tag:theconversation.com,2011:/global/topics/calories-14234/articlesCalories – The Conversation2023-10-10T21:43:33Ztag:theconversation.com,2011:article/2077232023-10-10T21:43:33Z2023-10-10T21:43:33ZWhat is the OMAD diet? Is one meal a day actually good for weight loss? And is it safe?<figure><img src="https://images.theconversation.com/files/551627/original/file-20231003-26-odr3p8.jpg?ixlib=rb-1.1.0&rect=152%2C26%2C5838%2C3449&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/female-bare-feet-weight-scale-bathroom-785794792">Shutterstock</a></span></figcaption></figure><p>What do British Prime Minister <a href="https://www.sciencefocus.com/the-human-body/one-meal-a-day-diet-omad">Rishi Sunak</a> and singer <a href="https://theconversation.com/one-meal-a-day-diet-popular-with-celebrities-could-do-more-harm-than-good-heres-why-203086">Bruce Springsteen</a> have in common?</p>
<p>They’re among an ever-growing group of public figures touting the benefits of eating just one meal a day.</p>
<p>As a result, the one meal a day (OMAD) diet is the latest attention-grabbing weight loss trend. Advocates claim it leads to fast, long-term weight loss success and better health, including delaying the ageing process. </p>
<p>Like most weight-loss programs, the OMAD diet makes big and bold promises. Here’s what you need to know about eating one meal a day and what it means for weight loss.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/whats-the-weight-set-point-and-why-does-it-make-it-so-hard-to-keep-weight-off-195724">What's the 'weight set point', and why does it make it so hard to keep weight off?</a>
</strong>
</em>
</p>
<hr>
<h2>The OMAD diet explained</h2>
<p>Essentially, the OMAD diet is a type of intermittent fasting, where you fast for 23 hours and consume all your daily calories in one meal eaten within one hour.</p>
<p>The OMAD diet rules are presented as simple and easy to follow:</p>
<ol>
<li><p>You can eat whatever you want, provided it fits on a standard dinner plate, with no calorie restrictions or nutritional guidelines to follow. </p></li>
<li><p>You can drink calorie-free drinks throughout the day (water, black tea and coffee). </p></li>
<li><p>You must follow a consistent meal schedule, eating your one meal around the same time each day.</p></li>
</ol>
<figure class="align-center ">
<img alt="Plate of chicken and veggies, next to a cup of dried fruit" src="https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551622/original/file-20231003-25-n2lo07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The one meal a day diet significantly restricts your calorie intake.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/ZjEeMnDiq00">Ella Olsson/Unsplash</a></span>
</figcaption>
</figure>
<p>Along with creating a calorie deficit, resulting in weight loss, advocates believe the OMAD diet’s extended fasting period <a href="https://www.frontiersin.org/articles/10.3389/fphys.2021.771944/full">leads to physiological changes</a> in the body that promote better health, including boosting your metabolism by triggering a process called ketosis, where your body burns stored fat for energy instead of glucose. </p>
<h2>What does the evidence say?</h2>
<p>Unfortunately, research into the OMAD diet is limited. Most studies have examined its impact on <a href="https://www.cell.com/cell-metabolism/pdf/S1550-4131(18)30512-6.pdf">animals</a>, and the <a href="https://pubmed.ncbi.nlm.nih.gov/35087416/">primary study</a> with humans involved 11 lean, young people following the OMAD diet for a mere 11 days.</p>
<p>Claims about the OMAD diet typically rely on research into intermittent fasting, rather than on the OMAD diet itself. There is <a href="https://www.cfp.ca/content/66/2/117.short">evidence</a> backing the efficacy of intermittent fasting to achieve weight loss. However, <a href="https://www.nature.com/articles/s41574-022-00638-x">most studies</a> have focused on short-term results only, typically considering the results achieved across 12 weeks or less.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-it-matter-what-time-of-day-i-eat-and-can-intermittent-fasting-improve-my-health-heres-what-the-science-says-203762">Does it matter what time of day I eat? And can intermittent fasting improve my health? Here's what the science says</a>
</strong>
</em>
</p>
<hr>
<p>One <a href="https://www.nejm.org/doi/full/10.1056/NEJMoa2114833">longer-term study from 2022</a> randomly assigned 139 patients with obesity to either a calorie-restricted diet with time-restricted eating between 8am and 4pm daily, or to a diet with daily calorie restriction alone for 12 months.</p>
<p>After 12 months, both groups had lost around the same weight and experienced similar changes in body fat, blood sugar, cholesterol and blood pressure. This indicates long-term weight loss achieved with intermittent fasting is not superior and on a par with that achieved by traditional dieting approaches (daily calorie restriction).</p>
<h2>So what are the problems with the OMAD diet?</h2>
<p><strong>1. It can cause nutritional deficiencies and health issues.</strong></p>
<p>The OMAD diet’s lack of nutritional guidance on what to eat for that one meal a day raises many red flags. </p>
<p>The meals we eat every day should include a source of protein balanced with wholegrain carbs, vegetables, fruits, protein and good fats to support <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071223/">optimum health, disease prevention and weight management</a>.</p>
<figure class="align-center ">
<img alt="Woman shops for groceries" src="https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551625/original/file-20231003-15-4yrdir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We’re likely to miss out on key nutrients if we eat one meal a day.</span>
<span class="attribution"><a class="source" href="https://www.pexels.com/photo/woman-in-green-shirt-looking-at-her-grocery-list-8422685/">Kampus Production/Pexels</a></span>
</figcaption>
</figure>
<p>Not eating a balanced diet will result in nutritional deficiencies that can result in poor immune function, fatigue and a decrease in bone density, leading to osteoporosis. </p>
<p>Fasting for 23 hours a day is also likely to lead to extreme feelings of hunger and uncontrollable cravings, which may mean you consistently eat foods that are not good for you when it’s time to eat. </p>
<p><strong>2. It’s unlikely to be sustainable.</strong></p>
<p>You might be able to stick with the OMAD diet initially, but it will wear thin over time. </p>
<p>Extreme diets – especially ones prescribing extended periods of fasting – aren’t enjoyable, leading to feelings of deprivation and social isolation during meal times. It’s hard enough to refuse a piece of office birthday cake at the best of times, imagine how this would feel when you haven’t eaten for 23 hours!</p>
<p>Restrictive eating can also lead to an unhealthy relationship with food, making it even harder to achieve and maintain a healthy weight. </p>
<p><strong>3. Quick fixes don’t work.</strong></p>
<p>Like other popular intermittent fasting methods, the OMAD diet appeals because it’s easy to digest, and the results appear fast. </p>
<p>But the OMAD diet is just another fancy way of cutting calories to achieve a quick drop on the scales. </p>
<p>As your weight falls, things will quickly go downhill when your <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4766925/">body activates its defence mechanisms</a> to defend your weight loss. In fact, it will regain weight – a response that stems from our hunter-gatherer ancestors’ need to survive periods of deprivation when food was scarce.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-it-true-the-faster-you-lose-weight-the-quicker-it-comes-back-heres-what-we-know-about-slow-and-fast-weight-loss-198301">Is it true the faster you lose weight the quicker it comes back? Here's what we know about slow and fast weight loss</a>
</strong>
</em>
</p>
<hr>
<h2>The bottom line</h2>
<p>Despite the hype, the OMAD diet is unsustainable, and it doesn’t result in better weight-loss outcomes than its predecessors. Our old habits creep back in and we find ourselves fighting a cascade of physiological changes to ensure we regain the weight we lost.</p>
<p>Successfully losing weight long-term comes down to:</p>
<ul>
<li><p>losing weight in small manageable chunks you can sustain, specifically periods of weight loss, followed by periods of weight maintenance, and so on, until you achieve your goal weight</p></li>
<li><p>making gradual changes to your lifestyle to ensure you form habits that last a lifetime.</p></li>
</ul>
<p><em>At the Boden Group, Charles Perkins Centre, we are studying the science of obesity and running clinical trials for weight loss. You can <a href="https://redcap.sydney.edu.au/surveys/?s=RKTXPPPHKY">register here</a> to express your interest.</em></p><img src="https://counter.theconversation.com/content/207723/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Nick Fuller works for the University of Sydney and has received external funding for projects relating to the treatment of overweight and obesity. He is the author and founder of the Interval Weight Loss program.</span></em></p>Like most weight-loss programs, the OMAD diet makes bold promises – and comes with risks.Nick Fuller, Charles Perkins Centre Research Program Leader, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2116132023-08-21T20:17:39Z2023-08-21T20:17:39ZCalories and kilojoules: how do we know the energy content of food, and how accurate are the labels?<figure><img src="https://images.theconversation.com/files/543631/original/file-20230821-17-t1wke.jpeg?ixlib=rb-1.1.0&rect=0%2C29%2C3888%2C2555&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Everything we consume contains energy our bodies use to move, grow and maintain health. To work out how much energy is in different foods and drinks, we need to first look at a few core concepts.</p>
<p>Firstly, you’ve probably heard of the units of measurement for energy – calories – as well as the metric equivalent, which is joules. One calorie is defined as the amount of energy required to raise the temperature of 1 gram of water by 1°C.</p>
<p>In human nutrition, the amounts of energy needed to maintain health, and to fuel a body, are much larger than the tiny singular calories used to heat up a gram of water. So, the term “calorie” in nutrition commonly refers to a <a href="https://www.sciencedirect.com/science/article/pii/S0022316622085546">kilocalorie</a> (or kcal), which is 1,000 calories. When you see the word “calories” on a nutrition label, it’s likely referring to kcals.</p>
<p>The energy stored in food and drinks is released when the body breaks down one or more of the four macronutrients inside the food (carbohydrates, proteins, fats, alcohol). The body then uses that energy for activities such as keeping our heart beating, our lungs breathing and our muscles moving. </p>
<p>When energy in food is estimated, it is the amount of energy food and drinks provide for these bodily processes. The four macronutrients provide <a href="https://www.sciencedirect.com/science/article/pii/S0002916522039454">different amounts of energy</a>:</p>
<ol>
<li> 1 gram of carbohydrate provides about 4 kcal of energy</li>
<li> 1 gram of fat provides about 9 kcal of energy</li>
<li> 1 gram of protein provides about 4 kcal of energy</li>
<li> 1 gram of alcohol provides about 7 kcal of energy.</li>
</ol>
<h2>How are calories estimated?</h2>
<p>There are two ways to estimate the amount of energy in food and drinks.</p>
<p>The first is called “bomb calorimetry”. This gold-standard method involves placing a small sample of food or drink inside a device known as a bomb calorimeter. The food is burned in the presence of oxygen, releasing heat. </p>
<p>The amount of heat released is directly related to the amount of energy in the food, allowing a calculation to be made. This method is most commonly used for foods rich in fats and is considered the most reliable (but expensive) method.</p>
<p>The second method, the Atwater system, is a much less expensive method for estimating energy content. It is more commonly used when calculating energy of most food and drinks sold in supermarkets. Named after legendary food researcher <a href="https://www.sciencedirect.com/science/article/pii/S0022316622065336">Wilbur Atwater</a>, this system uses a standard conversion factor for each macronutrient found in food and drinks. By estimating the amount of each of the four macronutrients, an approximate calculation of the total energy can be made. </p>
<p>However, this method requires detailed knowledge of the ingredients within composite foods (such as muesli bars or hamburgers) – which may reduce accuracy. There is also a margin of error to expect with the Atwater system, because it assumes each ingredient is always the same in composition. </p>
<p>For example, a cup of oats grown in one part of the country won’t necessarily have the exact same nutritional content as another cup of oats grown elsewhere, due to climate and soil differences. So, this system is an estimation based on an average.</p>
<p>Importantly, both methods estimate the amount of energy <em>in</em> food and drinks. But the actual energy our bodies extract from these foods and drinks can vary due to factors such as individual differences in digestion and absorption, as well as food processing and cooking methods.</p>
<h2>Why do foods have calories written on them?</h2>
<p>In Australia, it’s a <a href="https://www.foodstandards.gov.au/consumer/labelling/panels/Pages/default.aspx">legal requirement</a> for packaged food items to have a nutrition information panel that displays the number of kcal it contains. </p>
<p>However, homemade food items sold at places like a fresh market may not be required to provide a nutrition information panel. This will depend on the type of food being sold and the scale of the business operation.</p>
<p>Fresh foods such as fruit, vegetables and meat also don’t require a nutrition information panel. To find out the number of kcal in them, you can either run an experiment with a bomb calorimeter or look up an estimated value in an online nutrition database.</p>
<p>Food composition databases such as <a href="https://www.calorieking.com/us/en/">CalorieKing</a> compile information about the energy and nutrient content of various foods. Dietitians and other health professionals often use these databases to estimate the energy content of foods to inform dietary recommendations.</p>
<h2>Different international standards</h2>
<p>Both kJ and kcal refer to energy – they are just two different units of measurements (such as how inches and centimetres are two different units for measuring length). Kilojoules (kJ) is part of the International System of Units (SI).</p>
<p>Australia, New Zealand and some parts of Europe use kJ. The United States and the United Kingdom use kcal. To convert between calories and kilojoules you use the conversion factors: </p>
<ul>
<li>1 kcal = 4.184 kJ</li>
<li>1 kJ = 0.24 kcal (about ¼).</li>
</ul>
<p>For example, if you have a packet of chips with an energy content of 200 kcal, you can convert it to kJ as follows: 200 kcal × 4.184 = 836.8 kJ.</p>
<p>As for how many calories are acceptable to eat, the Australian Guidelines for Healthy Eating estimate the average adult requires about 7,000kJ or 1,670Kcal every day. However, differences in age, gender, size, health and physical activity will influence how much energy a person needs. </p>
<p>To estimate your personal energy requirements, you can use this <a href="https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients-dietary-energy-calculator#results-energy">nutrients and dietary energy calculator</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-time-to-bust-the-calories-in-calories-out-weight-loss-myth-199092">It's time to bust the 'calories in, calories out' weight-loss myth</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/211613/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lauren Ball works for The University of Queensland and receives funding from the National Health and Medical Research Council, Queensland Health, Royal Australian College of General Practitioners and Mater Misericordia. She is a Director of Dietitians Australia, a Director of the Darling Downs and West Moreton Primary Health Network and an Associate Member of the Australian Academy of Health and Medical Sciences.</span></em></p><p class="fine-print"><em><span>Emily Burch works for Southern Cross University. </span></em></p><p class="fine-print"><em><span>Katelyn Barnes works for The University of Queensland and ACT Health. </span></em></p>There are two main methods used to calculate the energy content in food and drinks.Lauren Ball, Professor of Community Health and Wellbeing, The University of QueenslandEmily Burch, Dietitian, Researcher & Lecturer, Southern Cross UniversityKatelyn Barnes, Postdoctoral Research Fellow, School of Human Movement and Nutrition Sciences, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1990922023-06-05T20:04:28Z2023-06-05T20:04:28ZIt’s time to bust the ‘calories in, calories out’ weight-loss myth<figure><img src="https://images.theconversation.com/files/526363/original/file-20230515-24510-h68d3e.jpg?ixlib=rb-1.1.0&rect=26%2C278%2C5964%2C3709&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-africanamerican-man-exercising-sunset-on-1810199758">Shutterstock</a></span></figcaption></figure><p>If you’ve ever tried to lose weight, there’s a good chance you’ve been told it all comes down to a simple “calories in, calories out” formula: burn more calories than you consume, and the kilos will disappear.</p>
<p>And it’s easy to see the appeal of breaking weight loss down into simple maths – just follow the formula, and you’ll achieve success. It’s also believable because many people do lose weight when they first adopt this approach.</p>
<p>Indeed, the diet industry’s reliance on the “calories in, calories out” concept is why society blames people for being overweight. Anyone who can’t follow this simple energy formula is only overweight because they lack the willpower to eat less and exercise more.</p>
<p>But the only simple truth here is that it’s time to bust the “calories in, calories out” myth as the only way to lose weight. Here’s why.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-exercise-help-you-lose-weight-198292">Does exercise help you lose weight?</a>
</strong>
</em>
</p>
<hr>
<h2>It’s nearly impossible to calculate accurately</h2>
<p>The many calorie-counting apps and online calculators available make it seem effortless. Simply enter your sex, age, height, weight, body composition and activity levels and they’ll tell you exactly how many calories you should eat daily to lose weight.</p>
<p>Unfortunately, no matter how accurate these calculators claim to be, they rely on averages and can’t determine the calorie intake appropriate for you with 100% accuracy. They can only estimate.</p>
<p>Similarly, our metabolic rate – how much energy we burn at rest – also varies from person to person based on many factors, including body composition or how much muscle and fat we have. Complicating things further, our metabolic rate also alters when we change our diet and lose weight.</p>
<figure class="align-center ">
<img alt="Brunch table with lots of food" src="https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526365/original/file-20230516-23656-jmyql3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Our metabolic rate varies from person to person.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/y3aP9oo9Pjc">Unsplash/Ali Inay</a></span>
</figcaption>
</figure>
<p>Calculating the calories in food – the other part of managing “calories in” – is also far from accurate. </p>
<p>While Australian food standards require foodstuffs to display Nutrition Information Panels showing energy in kilojoules, there are no requirements for information accuracy other than it must not be misleading. A worrying <a href="https://pubmed.ncbi.nlm.nih.gov/17077059/">+/-20% discrepancy is generally accepted</a> for the values shown on labels.</p>
<p>In practice, the variation can be much more than this. One Australian study found food contained anywhere <a href="https://pubmed.ncbi.nlm.nih.gov/17077059/">between 13% less and 61% more</a> energy or nutrient components than its packaging stated. </p>
<h2>Not all calories are created, or consumed, equally</h2>
<p>Another reason the simple “calories in, calories out” formula is not so simple is our bodies don’t consume every calorie the same way. What’s shown in your calorie counter is not what’s actually absorbed in your body. </p>
<p>Different calorie sources also have different effects on our hormones, brain response and energy expenditure, changing how we respond to and manage our food intake.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-last-5-kilos-really-are-the-hardest-to-lose-heres-why-and-what-you-can-do-about-it-195725">The last 5 kilos really are the hardest to lose. Here’s why, and what you can do about it</a>
</strong>
</em>
</p>
<hr>
<p>For example, while eating 180 calories worth of nuts is the same as eating 180 calories of pizza in terms of energy intake, the way these foods are absorbed and how they affect the body is very different.</p>
<p>While we absorb most of the calories in a slice of pizza, we don’t absorb about <a href="https://academic.oup.com/ajcn/article/100/suppl_1/412S/4576547?login=true">20% of the calories</a> in nuts because their fat is stored in the nut’s fibrous cell walls, which don’t break down during digestion. Nuts are also packed with fibre filling us up for longer, while a slice of pizza has us immediately reaching for another due to its low fibre content.</p>
<h2>Our bodies disrupt the formula</h2>
<p>The biggest failing of the “calories in, calories out” formula is it ignores that the body adjusts its control systems when calorie intake is reduced. So while the formula can support people achieving weight loss initially, the reduction in energy intake is <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5639963/">counteracted by mechanisms</a> that ensure lost weight is regained. </p>
<p>Namely, when your body registers a sustained decrease in the calories you consume, it believes its survival is threatened. So it automatically <a href="https://pubmed.ncbi.nlm.nih.gov/25896063/">triggers a series of physiological responses</a> to protect against the threat, reducing our metabolic rate and burning less energy.</p>
<p>This stems from our hunter-gatherer ancestors, whose bodies developed this response to adapt to periods of deprivation when food was scarce to protect against starvation. </p>
<figure class="align-center ">
<img alt="Dance class" src="https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526367/original/file-20230516-22708-w9tcrh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Our body slows our metabolism in response to weight loss.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/3ckWUnaCxzc">Unsplash/Danielle Cerullo</a></span>
</figcaption>
</figure>
<p>Research also suggests our bodies have a “<a href="https://theconversation.com/whats-the-weight-set-point-and-why-does-it-make-it-so-hard-to-keep-weight-off-195724">set point weight</a>”: a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990627/">genetically predetermined weight</a> our bodies try to maintain regardless of what we eat or how much we exercise. </p>
<p>Our bodies protect our set point as we lose weight, managing biological signals from the brain and hormones to hold onto fat stores in preparation for future reductions in our calorie intake.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/whats-the-weight-set-point-and-why-does-it-make-it-so-hard-to-keep-weight-off-195724">What's the 'weight set point', and why does it make it so hard to keep weight off?</a>
</strong>
</em>
</p>
<hr>
<p>The body achieves this in several ways, all of which directly influence the “calories in, calories out” equation, including:</p>
<ul>
<li><p><strong>slowing our metabolism</strong>. When we reduce our calorie intake to lose weight, we lose muscle and fat. This decrease in body mass results in an expected decrease in metabolic rate, but there is a <a href="https://pubmed.ncbi.nlm.nih.gov/7632212/">further 15% decrease in metabolism</a> beyond what can be accounted for, further disrupting the “calories in, calories out” equation. Even after we regain lost weight our metabolism <a href="https://pubmed.ncbi.nlm.nih.gov/27136388/">doesn’t recover</a>. Our thyroid gland also misfires when we restrict our food intake, and <a href="https://pubmed.ncbi.nlm.nih.gov/16322796/">fewer hormones are secreted</a>, also changing the equation by reducing the energy we burn at rest</p></li>
<li><p><strong>adapting how our energy sources are used</strong>. When we reduce our energy intake and start losing weight, our body <a href="https://pubmed.ncbi.nlm.nih.gov/7572701/">switches from using fat as its energy source</a> to carbohydrates and holds onto its fat, <a href="https://pubmed.ncbi.nlm.nih.gov/7572701/">resulting in less energy being burned</a> at rest</p></li>
<li><p><strong>managing how our adrenal gland functions</strong>. Our adrenal gland manages the hormone cortisol, which it releases when something that stresses the body – like calorie restriction – is imposed. Excess cortisol production and its presence in our blood <a href="https://pubmed.ncbi.nlm.nih.gov/10918539/">changes how our bodies process, store and burn fat</a>.</p></li>
</ul>
<figure class="align-center ">
<img alt="Greasy pizza" src="https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526369/original/file-20230516-17-5raf8w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Eating 180 calories worth of nuts is not the same as eating 180 calories of pizza in terms of energy intake.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/SU1LFoeEUkk">Unsplash/Alan Hardman</a></span>
</figcaption>
</figure>
<p>Our bodies also cleverly trigger responses aimed at increasing our calorie intake to regain lost weight, including: </p>
<ul>
<li><p><strong>adjusting our appetite hormones</strong>. When we reduce our calorie intake and deprive our bodies of food, our hormones work differently, <a href="https://pubmed.ncbi.nlm.nih.gov/22029981/">suppressing feelings of fullness</a> and telling us to eat more</p></li>
<li><p><strong>changing how our brain functions</strong>. When our calorie intake reduces, activity in our hypothalamus – the part of the brain that regulates emotions and food intake – also reduces, <a href="https://pubmed.ncbi.nlm.nih.gov/18568078/">decreasing our control</a> and judgement over our food choices.</p></li>
</ul>
<h2>Bottom line</h2>
<p>The “calories in, calories out” formula for weight loss success is a myth because it oversimplifies the complex process of calculating energy intake and expenditure. More importantly, it fails to consider the mechanisms our bodies trigger to counteract a reduction in energy intake. </p>
<p>So while you may achieve short-term weight loss following the formula, you’ll likely regain it. </p>
<p>What’s more, calorie counting can do more harm than good, taking the pleasure out of eating and contributing to developing an unhealthy relationship with food. That can make it even harder to achieve and maintain a healthy weight.</p>
<p>For long term weight loss, it’s important to follow evidence-based programs from health-care professionals and make gradual changes to your lifestyle to ensure you form habits that last a lifetime.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-menopause-making-me-put-on-weight-no-but-its-complicated-198308">Is menopause making me put on weight? No, but it's complicated</a>
</strong>
</em>
</p>
<hr>
<p><em>At the Boden Group, Charles Perkins Centre, we are studying the science of obesity and running clinical trials for weight loss. You can register for free <a href="https://redcap.sydney.edu.au/surveys/?s=RKTXPPPHKY">here</a> to express your interest.</em></p><img src="https://counter.theconversation.com/content/199092/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Nick Fuller works for the University of Sydney and has received external funding for projects relating to the treatment of overweight and obesity. He is the author and founder of the Interval Weight Loss program.</span></em></p>The diet industry’s reliance on the ‘calories in, calories out’ concept is why society blames people for being overweight. But it’s a myth.Nick Fuller, Charles Perkins Centre Research Program Leader, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1918252022-10-11T15:12:01Z2022-10-11T15:12:01ZWhy food labels showing the exercise needed to burn off calories won’t work for everyone<figure><img src="https://images.theconversation.com/files/488750/original/file-20221007-26-edpaj4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Knowing how much exercise it takes to burn the calories in certain foods may be easier for consumers to understand.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cheerful-handsome-african-american-guy-sportsman-2198788187">Prostock-studio/ Shutterstock</a></span></figcaption></figure><p>In an effort to tackle the <a href="https://www.gov.uk/government/statistics/statistics-on-obesity-physical-activity-and-diet-england-2020-ns">increasing prevalence of obesity</a>, the UK government has introduced a number of public health strategies over the years, including changes to how we label foods. For example, the “<a href="https://www.food.gov.uk/safety-hygiene/check-the-labe">traffic light</a>” colour-coding system, which was introduced in 2013, aims to make it <a href="https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003765">easier for consumers</a> to know whether or not the foods they’re eating are healthy for them. </p>
<p>But some critics feel that <a href="https://www.cambridge.org/core/journals/public-health-nutrition/article/colour-correct-the-interactive-effects-of-food-label-nutrition-colouring-schemes-and-food-category-healthiness-on-health-perceptions/6A88980505E4ACF910BC01564F85F2B2">this kind of labelling</a> may still be difficult for people to fully understand or practically apply, and may not necessarily lead to people choosing healthier food. Given obesity is <a href="https://www.gov.uk/government/statistics/obesity-profile-update-july-2022/obesity-profile-short-statistical-commentary-july-2022">still on the rise</a>, it’s clear current strategies aren’t working. </p>
<p>Recently, a team of researchers from Loughborough University proposed a <a href="https://www.lboro.ac.uk/schools/sport-exercise-health-sciences/news/2022/foodlabellingandphysicalactivity/">different system of food labelling</a> known as “physical activity calorie equivalent”, or Pace. This method illustrates how many minutes of exercise it would take to burn the calories in certain foods and drinks. The researchers showed that this new approach was easier for participants to understand – and may be more likely to help people avoid high-calorie foods. </p>
<p>But while these types of food labels have the benefit of being easier to understand, they could also run the risk of being misleading – and may not work for everyone.</p>
<h2>The benefits</h2>
<p>Alongside being easier to understand, the team from Loughborough also showed in a previous review that using exercise to illustrate the equivalent calories in food and drinks can help people <a href="https://pubmed.ncbi.nlm.nih.gov/31822568/">consume fewer calories</a> – around 65 fewer calories every time they ate – compared with other food labelling methods. </p>
<p>While this may not sound like much, over time it may help people <a href="https://www.bmj.com/content/363/bmj.k4867">over-eat less</a> and may also result in them <a href="https://pubmed.ncbi.nlm.nih.gov/26222056/#:%7E:text=Physical%20activity%20calorie%20equivalent%20%28PACE%29%20labels%20are%20an,fast%20food%20meals%20while%20encouraging%20patrons%20to%20exercis">eating fewer high-calorie foods</a> such as fast food. </p>
<p><a href="https://link.springer.com/article/10.1186/1475-2891-12-72">Other studies</a> have shown that Pace may also help <a href="https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-019-7960-1">increase physical activity levels</a> somewhat, which could be beneficial for those looking to be more active.</p>
<p>Using exercise to illustrate the calories in food may therefore be a useful tool for consumers as it provides understandable, relatable information that may help them <a href="https://www.sciencedirect.com/science/article/abs/pii/S0091743521003820?via%3Dihub">better plan</a> their <a href="https://www.sciencedaily.com/releases/2016/04/160406202430.htm">meals and workouts</a> – potentially leading to healthier food choices while encouraging physical activity, both of which are key in reducing or preventing obesity. </p>
<h2>The downsides</h2>
<p>While initial findings on exercise-based food labels seem promising, research is <a href="https://www.sciencedirect.com/science/article/abs/pii/S0091743521003820?via%3Dihub">still needed in real-world settings</a> and over <a href="https://www.bmj.com/content/353/bmj.i1856/rr-1">longer periods of time</a> if it’s going to inform future public health policy.</p>
<figure class="align-center ">
<img alt="An elderly couple take a walk outdoors." src="https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=456&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=456&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=456&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=574&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=574&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488752/original/file-20221007-18-zob8st.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=574&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Age is just one of the factors that affects how you burn calories.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/elderly-couple-walking-on-trail-exercise-724237843">LanaG/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Another clear pitfall of the Pace approach is that it <a href="https://ajph.aphapublications.org/doi/full/10.2105/AJPH.2011.300350">generalises calories burnt</a>. This means that the averages used on labels may not actually be true of how each person burns calories. </p>
<p>A <a href="https://pubmed.ncbi.nlm.nih.gov/27348753/">variety of factors</a> – such as the type of exercise you’re doing, how <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2278845/">intensely you’re exercising</a>, your age and <a href="https://www.jci.org/articles/view/114857">fitness level</a> – all influence the amount of calories you burn. The way we digest and metabolise foods is also <a href="https://www.nature.com/articles/ijo2008246">highly individual</a>. </p>
<p>This could mean that general food labels could be deceptive. It’s unlikely that the calories estimated to be burnt on the packet will apply to everyone. This could lead to some people eating more or less food than they need. </p>
<p>Another reason the information on these labels could be misleading is that it makes the assumption that all calories consumed are equal. For example, two foods with the same calorie content may have different levels of fibre, fat, sugars or protein. </p>
<p>All of these are <a href="https://theconversation.com/not-all-calories-are-equal-a-dietitian-explains-the-different-ways-the-kinds-of-foods-you-eat-matter-to-your-body-156900">metabolised differently</a>, which will influence how our foods are used and stored by our body. Low-fibre, <a href="https://pubmed.ncbi.nlm.nih.gov/16762948/">high-sugar, energy-dense foods</a>, for example, have been <a href="https://pubmed.ncbi.nlm.nih.gov/27104562/">associated with weight gain</a> compared with healthier options containing a similar number of calories. </p>
<p>Pace labels could also inadvertently encourage people to <a href="https://bmcobes.biomedcentral.com/articles/10.1186/s40608-014-0021-5">eat more poor-quality or ultra-processed foods</a> as they may feel they can just exercise to burn those calories off. However, <a href="https://pubmed.ncbi.nlm.nih.gov/21211100/">unhealthy, ultra-processed foods</a> can still <a href="https://pubmed.ncbi.nlm.nih.gov/33942057/">cause harm</a> to the body, even if the calories in them are used. </p>
<p>Other experts feel that such types of food label will only have a <a href="https://www.bmj.com/content/353/bmj.i1856/rr-1">short-term effect</a> in changing food choices. Another concern is that Pace could trigger eating disorders or <a href="https://www.bbc.co.uk/news/uk-50743683">over-exercise</a> in susceptible populations. It could also lead people to eat less so they can avoid doing the exercise required to burn off additional calories. </p>
<h2>Our view</h2>
<p>Labelling foods and drinks with the amount of exercise needed to burn them off may certainly have some benefits. However, it’s clear that a one-size-fits-all approach may be too simplistic when it comes to tackling obesity in a population. This is especially true when considering that every person’s diet, activity levels, lifestyle habits and even genetics are different from the next. </p>
<p>As such, strategies for reducing obesity should aim to take a more individualised approach to helping people increase their total daily <a href="https://pubmed.ncbi.nlm.nih.gov/12468415">movement and activity</a>, while also helping them evaluate their eating patterns and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105579/">portion sizes</a>, as well as choosing better-quality foods.</p><img src="https://counter.theconversation.com/content/191825/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>While these kinds of food labels may be easier to understand, they run the risk of being too generalised.Justin Roberts, Associate Professor, Health and Exercise Nutrition, Anglia Ruskin UniversityHenry Chung, Lecturer in Sport and Exercise Science, University of EssexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1867752022-09-09T15:19:42Z2022-09-09T15:19:42ZWeight loss: the time of day you eat your biggest meal has little effect – new study<figure><img src="https://images.theconversation.com/files/483564/original/file-20220908-4832-1jcbli.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C4737%2C3165&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/traditional-english-breakfast-image-isolated-on-89940679">Jan Mika/Shutterstock</a></span></figcaption></figure><p>Some of the most popular diet advice in recent years has centred around the idea that the right timing for your meals can make a big difference in the amount of weight you lose. It was long said that if you wanted to lose weight it was best to eat a large meal at the beginning of the day and keep any later meals smaller. </p>
<p>The logic behind this theory is understandable, especially given that almost every cell in the body follows the same 24-hour cycle that we do. Circadian clocks are found throughout the body and regulate the daily rhythms of most of our biological functions, including metabolism. </p>
<p>Because of these metabolic rhythms, scientists have proposed that the way in which we process meals varies at different times of the day. This field of research is called “<a href="https://onlinelibrary.wiley.com/doi/10.1111/jnc.15246">chrono-nutrition</a>”, and it has great potential for helping to improve people’s health.</p>
<p><a href="https://onlinelibrary.wiley.com/doi/10.1002/oby.20460">Two studies from 2013</a> suggested that consuming more calories <a href="https://www.nature.com/articles/ijo2012229">early in the day</a> and fewer calories in the evening helps people lose weight. Yet a <a href="https://www.cell.com/cell-metabolism/fulltext/S1550-4131(22)00344-8">major new study</a> has found that while the relative size of breakfast and dinner influences self-reported appetite, it has no effect on metabolism and weight loss.</p>
<p>To investigate the link between the size of breakfast and dinner and their effect on hunger, a team of researchers at the universities of Aberdeen and Surrey conducted a controlled study in healthy but overweight people. The participants were fed two diets, each for four weeks: a big breakfast and a small dinner, and a small breakfast with a big dinner. We kept lunches the same. </p>
<p>We provided all of the meals so we knew exactly how many calories study participants were consuming. We measured the participants’ metabolism, including monitoring how many calories they burned.</p>
<p>All study participants undertook both diet conditions so that the effect of meal patterns could be compared in the same people.</p>
<p>We predicted that a big breakfast and small dinner would increase calories burned and weight lost. Instead, the results of the experiment found no differences in body weight or any biological measures of energy usage between the two meal patterns. </p>
<p>Measures of energy usage included basal metabolic rate (how many calories your body uses at rest), physical activity, and use of a chemical form of water that enables assessment of <a href="https://doi.org/10.1016/j.xcrm.2021.100203">total daily energy use</a>.</p>
<p>There were also no differences in daily levels of blood glucose, insulin or lipids. This is important because changes of these factors in the blood are associated with metabolic health. </p>
<p><a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658129/">Our findings are consistent</a> with short-term (one to six days) <a href="https://doi.org/10.3945/ajcn.116.151332">meal-timing studies</a>, where participants live in a laboratory respiratory chamber (a small, air-tight room equipped with basic comforts) for the duration of the experiment. Together, the research suggests that the way our bodies process calories in the morning versus the evening does not influence weight loss in the way that has been reported in other studies.</p>
<figure class="align-center ">
<img alt="A picture of a plate on a table with a fork and knife on either side of it. In the centre of the plate is an old alarm clock." src="https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/483731/original/file-20220909-18-x59nuw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">When you decide to have your biggest meal of the day is up to you.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/alarm-clock-inside-plate-675866614">nehophoto/ Shutterstock</a></span>
</figcaption>
</figure>
<p>In our study, the only difference was a change in the self-reported feeling of hunger and related factors, such as the quantity of food they wanted to eat. Across the day, the meal pattern of big breakfast and small dinner caused participants to report less hunger throughout the day. This effect may be useful for people looking to lose weight, as it may help them better control their hunger and eat less. </p>
<p>As with all research, there were some limitations to our study. We only studied participants for four weeks for each meal pattern. <a href="https://www.nature.com/articles/ijo2012229">Past research</a> has shown the largest differences in the effects of early versus late energy intake <a href="https://onlinelibrary.wiley.com/doi/10.1002/oby.20460">after four weeks</a>. However, the fact that neither calories eaten nor calories burned changed over four weeks shows that body weight is unlikely to have changed if the study was longer.</p>
<p>Participants in the study were also allowed to choose the exact time of each meal. Despite this, there was a negligible difference in timing in each meal pattern.</p>
<p>Chrono-nutrition remains an exciting research area and there’s increasing evidence that meal timing can play an important role in improving the health of many people. However, our latest research indicates that the time of day you eat your biggest meal is not as important for weight loss as previously thought.</p><img src="https://counter.theconversation.com/content/186775/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Johnston receives funding from BBSRC, MRC, The Colt Foundation. He has performed consultancy work for Kellogg Marketing and Sales Company (UK) Limited, and collaborated with the Nestlé Institute of Health Sciences.</span></em></p><p class="fine-print"><em><span>Alex Johnstone receives funding from UKRI, The University of Aberdeen, The Scottish Government, National Health Service Endowments award, Tennovus Charity, Chief Scientist Office and European Community.</span></em></p><p class="fine-print"><em><span>Peter Morgan receives funding from Scottish Government and the Medical Research Council. In the past he has received funding from the BBSRC as well as from the pharmaceutical industry.</span></em></p>Previous studies suggested it was better to consume the bulk of your calories early in the day.Jonathan Johnston, Professor of Chronobiology and Integrative Physiology, University of SurreyAlex Johnstone, Personal Chair in Nutrition, The Rowett Institute, University of AberdeenPeter Morgan, Chair professor, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1827262022-07-19T17:34:43Z2022-07-19T17:34:43ZWarsaw Ghetto’s defiant Jewish doctors secretly documented the medical effects of Nazi starvation policies in a book rediscovered on a library shelf<figure><img src="https://images.theconversation.com/files/474632/original/file-20220718-76232-8ep20p.jpg?ixlib=rb-1.1.0&rect=120%2C111%2C1165%2C793&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The book includes haunting photos from inside the ghetto, along with its record of the medical effects of starvation.</span> <span class="attribution"><span class="source">'Maladie de Famine," American Joint Distribution Committee</span></span></figcaption></figure><p>In 1942, a group of starving Jewish scientists and doctors in the Warsaw Ghetto were collecting data on their starving patients. They hoped their research would benefit future generations through better ways to treat malnutrition, and they wanted the world to know of Nazi atrocities to prevent something similar from ever happening again. They recorded the grim effects of an almost complete lack of food on the human body in a rare book titled “<a href="https://www.worldcat.org/title/maladie-de-famine-recherches-cliniques-sur-la-famine-executees-dans-le-ghetto-de-varsovie-en-1942/oclc/613124708">Maladie de Famine</a>” (in English, “The Disease of Starvation: Clinical Research on Starvation in the Warsaw Ghetto in 1942”) that we <a href="https://dl.tufts.edu/concern/pdfs/h415pr96d">rediscovered in the Tufts University library</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="yellowed frontispiece of a book" src="https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=830&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=830&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=830&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1042&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1042&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474374/original/file-20220715-4647-pxtnux.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1042&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This French translation was donated to the Tufts University library in 1948.</span>
<span class="attribution"><span class="source">'Maladie de Famine,' American Joint Distribution Committee</span></span>
</figcaption>
</figure>
<p><a href="https://scholar.google.com/citations?user=HyTsVigAAAAJ&hl=en&oi=ao">As scientists who</a> <a href="https://scholar.google.com/scholar?q=irwin%20rosenberg&btnG=&hl=en&as_sdt=0%2C22">study starvation</a>, its biological effects and its use as a weapon of mass destruction, we believe the story of how and why Jewish scientists conducted this research in such extreme conditions is as important and compelling as its results. </p>
<p>The clandestine project’s lead doctor, Israel Milejkowski, wrote the books’s foreword. In it, he explains:</p>
<blockquote>
<p>“The work was originated and pursued under unbelievable conditions. I hold my pen in my hand and death stares into my room. It looks through the black windows of sad empty houses on deserted streets littered with vandalized and burglarized possessions. … In this prevailing silence lies the power and the depth of our pain and the moans that one day will shake the world’s conscience.”</p>
</blockquote>
<p>Reading these words, we were both transfixed, transported by his voice to a time and place where starvation was being used as a weapon of oppression and annihilation as the Nazis were systematically exterminating all Jews in their occupied territories. As scholars of starvation, we were also well aware that this book catalogs many of the justifications for the <a href="https://www.icrc.org/en/doc/war-and-law/treaties-customary-law/geneva-conventions/overview-geneva-conventions.htm">1949 Geneva Conventions</a>, which made starvation of civilians a war crime.</p>
<iframe src="https://embed.acast.com/60087127b9687759d637bade/63ce902162c0100011034184" frameborder="0" width="100%" height="190px"></iframe>
<p><iframe id="tc-infographic-561" class="tc-infographic" height="100" src="https://cdn.theconversation.com/infographics/561/4fbbd099d631750693d02bac632430b71b37cd5f/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>A defiant medical record</h2>
<p>Within months of their 1939 invasion of Poland, Nazi forces created the infamous Warsaw Ghetto. At its peak, more than <a href="https://www.jstor.org/stable/26627292">450,000 Jews were required to live in this small, walled-off area</a> of about 1.5 square miles (3.9 square kilometers) within the city, <a href="https://doi.org/10.2307/4065270">unable to leave even to look for food</a>.</p>
<p>Although Germans in Warsaw were allotted a <a href="https://hekint.org/2022/01/06/the-warsaw-ghetto-hunger-study/">daily ration of about 2,600 calories</a>, physicians in the ghetto estimated that Jews were able to consume only about 800 calories a day on average through a combination of rations and smuggling. That’s about half the calories volunteers consumed in <a href="https://doi.org/10.1093/jn/135.6.1347">a study on starvation</a> conducted near the end of World War II by researchers at the University of Minnesota, and less than a <a href="https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf">third of the average energy needs of an adult male</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="emaciated naked patient sits on hospital bed with nurse behind" src="https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=742&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=742&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=742&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=932&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=932&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474375/original/file-20220715-16-4kqicm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=932&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Even before mass deportations to death camps, many thousands of Jews died because of conditions within the Warsaw Ghetto.</span>
<span class="attribution"><span class="source">'Maladie de Famine,' American Joint Distribution Committee</span></span>
</figcaption>
</figure>
<p>When the Nazis designated the district of the Warsaw Ghetto, it enclosed two hospitals, one serving Jewish adults and another for Jewish children. The hospitals were allowed to continue to treat patients with whatever resources they could obtain, but Jews in general were <a href="https://www.archives.gov/publications/prologue/2010/winter/nuremberg.html">forbidden from conducting research</a>. Nevertheless, starting in February 1942, a group of Jewish doctors in the ghetto defied their captors by meticulously and secretly gathering data and observations on multiple biological aspects of starvation.</p>
<p>Then on July 22, 1942, Nazi forces entered the ghetto and destroyed the hospitals and other critical services. Patients and some of the doctors were killed outright or deported to be gassed, their laboratories, samples and some of their research destroyed.</p>
<p>With their own demise approaching, the remaining doctors spent the last nights of their lives meeting secretly in the cemetery buildings, transforming their data into a series of research articles. By October, as they put the finishing touches on the book, about <a href="https://encyclopedia.ushmm.org/content/en/article/deportations-to-and-from-the-warsaw-ghetto">300,000 Jews from the ghetto had already been gassed</a>. The physicians’ own data showed that another 100,000 had been killed through forced starvation and disease.</p>
<p>With final deportations of the few surviving Jews underway and his own death imminent, Milejkowski wrote of the dark, yawning emptiness of the ghetto at that moment, and the horrifying conditions the doctors had labored under to conduct and record the research. </p>
<p>Milejkowski had words for not only the reader, but also his dear colleagues, many of whom had already been executed.</p>
<blockquote>
<p>“What can I tell you, my beloved colleagues and companions in misery. You are a part of all of us. Slavery, hunger, deportation, those death figures in our ghetto were also your legacy. And you, by your work, could give the henchman the answer ‘Non omnis moriar,’ [I shall not wholly die].”</p>
</blockquote>
<p>The team’s act of resistance through science was its way to wring something good out of an evil situation, to show the world the quality of the Jewish doctor, but mostly to defy the Nazis’ intent to erase their existence.</p>
<p>With death knocking on the door, the doctors smuggled their precious research out of the ghetto to a sympathizer who buried it in the cemetery of the Warsaw hospital. Less than a year later, all but a few of the 23 authors were dead.</p>
<p>Immediately after the war, the manuscript was dug up and taken to one of the few surviving authors, Dr. Emil Apfelbaum, and the American Joint Distribution Committee in Warsaw, a charity whose main purpose at the time was to help <a href="https://www.jdc.org/video/75-years-later-remembering-jdcs-role-in-saving-wwii-survivors">Jewish survivors</a>. Together, they made the final edits and printed the six surviving articles, binding them into a book along with photos taken in the ghetto. Apfelbaum died just a couple of months before the final printing, broken by his years in the ghetto.</p>
<p>In 1948 and 1949, the American Joint Distribution Committee disseminated 1,000 copies of the French translation to hospitals, medical schools, libraries and universities across the U.S. It was one humble, crumbling copy of this book that waited to be “rediscovered” about 75 years later in the basement of a Tufts University library.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="black and white photo of an emaciated boy lying on a bed" src="https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474631/original/file-20220718-61161-bd2k07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many of the ghetto’s inhabitants had no other diseases beyond the effects of starvation.</span>
<span class="attribution"><span class="source">'Maladie de Famine,' American Joint Distribution Committee</span></span>
</figcaption>
</figure>
<h2>The book’s grim descriptions</h2>
<p>Based on observations of thousands of deaths from starvation, this research from the Warsaw Ghetto provides insight into the biological progression of starvation that scientists now are just beginning to understand.</p>
<p>For example, many Warsaw Ghetto residents who died of starvation were otherwise free of disease. The ghetto researchers found that while an otherwise healthy body diminished through starvation apparently had a decreased need for vitamins, the need for certain minerals remained. They saw few cases of scurvy (vitamin C deficiency), night blindness (vitamin A deficiency) or rickets (vitamin D deficiency). But they did see significant osteomalacia, a softening of the bones, as the body mined them for their stores of minerals.</p>
<p>When the doctors provided sugar to the severely malnourished, their energy-starved cells quickly absorbed it. This demonstrated that the ability to quickly absorb and use energy remained to the end, suggesting that energy was the single most important factor in starvation, not other micro- or macronutrients.</p>
<p>Each of these observations invites us as scientists to explore further. And with these lessons we can hope to prevent deaths or long-term harm from starvation through better treatment for the severely malnourished.</p>
<p>As scientists studying starvation today, it would be <a href="https://www.ama-assn.org/system/files/2019-01/code-of-medical-ethics-chapter-7.pdf">unthinkable and unethical to starve people</a> to learn how the human body adjusts and changes during the end stages of extreme starvation. Even if researchers go into a famine-stricken population to learn about starvation, they immediately treat the victims, erasing the very object of their research.</p>
<p>Partly as a result of the experience of the Warsaw Ghetto, the Geneva Conventions made <a href="https://ihl-databases.icrc.org/applic/ihl/ihl.nsf/Article.xsp?action=openDocument&documentId=ACF5220D585326BCC12563CD0051E8B6">intentional mass starvation a crime</a>, further strengthened by a U.N. Security Council Resolution <a href="https://www.un.org/press/en/2018/sc13354.doc.htm">as recently as 2018</a>. Nevertheless, this inhumane aspect of war <a href="https://theconversation.com/starving-civilians-is-an-ancient-military-tactic-but-today-its-a-war-crime-in-ukraine-yemen-tigray-and-elsewhere-184297">remains to this day</a>, as evidenced by current events in <a href="https://www.politico.eu/article/the-starvation-of-a-nation-how-putin-is-using-hunger-as-a-weapon-in-ukraine/">Ukraine</a> and <a href="https://www.economist.com/leaders/2021/10/09/ethiopia-is-deliberately-starving-its-own-citizens">Tigray</a>, Ethiopia.</p>
<p>Though “Maladie de Famine” has never been totally lost or forgotten, the lessons from the doctors’ research have faded to semi-obscurity. Eight decades after the destruction that ended their studies, we hope to shine a renewed light on this work and its enduring impact on physicians’ understanding of starvation and how to treat it. The unique data and observations regarding severe starvation that the Warsaw Ghetto doctors, despite their own suffering, presented in this precious book can even now help safeguard others from that same fate.</p>
<hr>
<p><em>The Joint Distribution Committee, which holds the copyright for “Maladie de Famine,” has allowed Tufts University to post a freely accessible <a href="https://dl.tufts.edu/concern/pdfs/h415pr96d">scan of the book</a> online.</em></p><img src="https://counter.theconversation.com/content/182726/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The story behind the research can be as compelling as the results. Recording the effects of starvation, a group of Jewish doctors demonstrated their dedication to science – and their own humanity.Merry Fitzpatrick, Research Assistant Professor of Nutrition Science and Policy, Tufts UniversityIrwin Rosenberg, Professor Emeritus of Nutrition and Medicine, Tufts UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1860882022-06-30T14:25:25Z2022-06-30T14:25:25ZWinning the Tour de France requires subtle physics, young muscles and an obscene amount of calories – 3 essential reads<figure><img src="https://images.theconversation.com/files/471684/original/file-20220629-15-kvfn1y.jpg?ixlib=rb-1.1.0&rect=23%2C52%2C2992%2C2053&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Last year's Tour de France winner was Tadej Pogacar, in the yellow jersey here – his second consecutive Tour title.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/tadej-pogacar-followed-by-jonas-vingegaard-during-the-climb-news-photo/1234302769?adppopup=true">SOPA Images/LightRocket via Getty Images</a></span></figcaption></figure><p>The <a href="https://www.letour.fr/en/">2022 Tour de France is here</a>. Starting in Copenhagen on July 1, the tour <a href="https://www.letour.fr/en/overall-route">covers almost 2,100 miles (3,380 kilometers)</a> over 24 days of riding through Denmark, Belgium, Switzerland and France. The tour is a feat of human athleticism, but to really understand how incredible it is to complete the race – much less win it – requires thinking about a unique blend of physics, biology and physiology. Mix those up just right and you get a Tour de France champion.</p>
<p>Over the years, The Conversation has published a series of stories covering the science of the Tour de France and elite athletics. Below are excerpts from three of those stories to help you better appreciate this spectacular race.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A wood engraving of two people riding old-school big wheel bikes." src="https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=520&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=520&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=520&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=654&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=654&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471687/original/file-20220629-22-3rg1tr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=654&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bicycles have changed a lot since they were first invented in the early 1800s, but the principles of keeping the bike below the rider’s center of gravity remain the same.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:The_American_Velocipede.jpg#/media/File:The_American_Velocipede.jpg">Theodore R. Davis / Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>1. The biomechanics of riding a bike</h2>
<p>Riding a bike is an easy thing to do once you learn, but the physics of how bikes and riders work together is surprisingly complicated. As <a href="https://scholar.google.com/citations?user=7XdBQfAAAAAJ&hl=en&oi=ao">Stephen Cain, a mechanical engineer</a> at West Virginia University, explains, “A big part of balancing a bicycle has to do with controlling the center of mass of the rider-bicycle system.” Basically, you have to keep the center of mass above the wheels – otherwise you tip over. </p>
<p>“Bicycle riders can use two main balancing strategies: steering and body movement relative to the bike,” says Cain. Steering keeps the bike underneath you while body movements subtly shift your center of gravity. Cain and his colleagues ran a study to understand the difference between how novice and professional cyclists balance a bike, and as he says in his article, they found that “both novice and expert riders exhibit similar balance performance at slow speeds. But at higher speeds, expert riders achieve superior balance performance by employing smaller but more effective body movements and less steering.” </p>
<p>This fine-scale control is why the racers in the Tour de France barely look like they are steering at all. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-mysterious-biomechanics-of-riding-and-balancing-a-bicycle-55093">The mysterious biomechanics of riding – and balancing – a bicycle</a>
</strong>
</em>
</p>
<hr>
<h2>2. How many calories do Tour riders burn?</h2>
<p>Think back to the last time you did some hard exercise and how hungry you were that evening. Now imagine how hungry you would be if you needed to ride your bike over 100 miles (165 km) and climb nearly 10,000 feet (about 3,050 meters) of elevation in less than five hours. This is what racers will have to do during Stage 12 of this year’s race as they traverse mountain passes through the French Alps. As <a href="https://scholar.google.com/citations?user=eHzYy_EAAAAJ&hl=en&oi=ao">Eric Goff, a sports physicist</a> at the University of Lynchburg explains, the cyclists are going to need a lot of fuel to pull this off. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pile of hamburgers." src="https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=335&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=335&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=335&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=421&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=421&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471689/original/file-20220629-26-6ezm1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=421&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Riders will burn around 120,000 calories over the course of the race, roughly equivalent to 210 Big Mac hamburgers.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/set-of-tasty-and-delicious-burgers-royalty-free-image/1318786684">Arbi Lena / iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>“To make a bicycle move, a Tour de France rider transfers energy from his muscles, through the bicycle and to the wheels that push back on the ground,” says Goff. Professional cyclists are in another league when it comes to producing power with their legs, but they are still limited by basic human biology. “Muscles, like any machine, can’t convert 100% of food energy directly into energy output,” explains Goff. “Muscles can be anywhere between 2% efficient when used for activities like swimming and 40% efficient in the heart.”</p>
<p>With mountains to climb and glory to claim, riders need to fuel their muscles with food. In his story, Goff calculates that over the course of the Tour de France, racers will burn an astonishing 120,000 calories – the equivalent of about 210 Big Macs.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tour-de-france-how-many-calories-will-the-winner-burn-163043">Tour de France: How many calories will the winner burn?</a>
</strong>
</em>
</p>
<hr>
<h2>3. Biology explains why professional athletes are young</h2>
<p>When you watch the Tour de France, soccer’s World Cup or the Olympics, it’s common to see a young teenage phenom, but it’s rare for anyone over the age of 40 to be competing.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/LVVwm9EM4XM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Professional cyclists are some of the fittest people on the planet, able to race up hills after biking for a hundred miles.</span></figcaption>
</figure>
<p><a href="https://scholar.google.com/citations?user=4-73LroAAAAJ&hl=en&oi=ao">Roger Fielding, an aging and exercise researcher</a> at Tufts University, writes that “old and young people build muscle in the same way.” But there is a biological reason no 50-year-old has ever won the Tour de France: “As you age, many of the biological processes that turn exercise into muscle become less effective.”</p>
<p>Muscles grow thanks to a number of complicated cellular pathways that are activated during exercise. When this network of receptors and signaling chemicals gets triggered, the body responds by increasing muscle size – and even makes some small tweaks to what genes are active. But as Fielding explains, in older people “the signal telling muscles to grow is much weaker for a given amount of exercise. These changes begin to occur when a person reaches around 50 years old and become more pronounced as time goes on.” </p>
<p>Many people can and do get into the best shape of their lives when they are in their 50s or 60s. But the fact that it is harder to get fit as you age is a major reason why it’s so important for older people to exercise – and why you won’t see any retirees leading the peloton in the Tour de France. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/50-year-old-muscles-just-cant-grow-big-like-they-used-to-the-biology-of-how-muscles-change-with-age-172941">50-year-old muscles just can’t grow big like they used to – the biology of how muscles change with age</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/186088/count.gif" alt="The Conversation" width="1" height="1" />
Three scientists explain the biology and physics of what goes into one of the world’s most grueling races, the Tour de France.Daniel Merino, Associate Breaking News Editor and Co-Host of The Conversation Weekly PodcastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1860972022-06-30T12:23:47Z2022-06-30T12:23:47ZTour de France: How many calories will the winner burn?<figure><img src="https://images.theconversation.com/files/471704/original/file-20220629-22-qb8z5u.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4132%2C3229&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Tour de France is one of the most physically taxing sporting feats imaginable.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/team-uae-emirates-tadej-pogacar-of-slovenia-wearing-the-news-photo/1233993203?adppopup=true">Phillippe Lopez/AFP via Getty Images</a></span></figcaption></figure><figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=255&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=255&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=255&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=321&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=321&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=321&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">CC-BY-ND.</span>
</figcaption>
</figure>
<p>Imagine you begin pedaling from the <a href="https://www.letour.fr/en/stage-12">start of Stage 12</a> of <a href="https://www.letour.fr/en">this year’s Tour de France</a>. Your very first task would be to bike approximately 20.6 miles (33.2 km) up to the peak of <a href="https://www.cyclinglocations.com/col-du-galibier-alps/">Col du Galibier</a> in the French Alps while gaining around 4,281 feet (1,305 m) of elevation. But this is only the first of three big climbs in your day. Next you face the peak of <a href="https://climbfinder.com/en/climbs/col-de-la-croix-de-fer">Col de la Croix de Fer</a> and then end the 102.6-mile (165.1-km) stage by taking on the famous <a href="https://climbfinder.com/en/climbs/alpe-d-huez">Alpe d'Huez</a> climb with its 21 serpentine turns. </p>
<p>On the fittest day of my life, I might not even be able to finish Stage 12 – much less do it in anything remotely close to the five hours or so the winner will take to finish the ride. And Stage 12 is just one of 21 stages that must be completed in the 24 days of the tour.</p>
<hr>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/tour-de-france-how-many-calories-will-the-winner-burn-186097&bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/us/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<p><a href="https://scholar.google.com/citations?user=eHzYy_EAAAAJ&hl=en&oi=ao">I am a sports physicist</a>, and I’ve <a href="http://johnericgoff.blogspot.com/">modeled the Tour de France</a> for nearly two decades using terrain data – like what I described for Stage 12 – and the laws of physics. But I still cannot fathom the physical capabilities needed to complete the world’s most famous bike race. Only an elite few humans are capable of completing a Tour de France stage in a time that’s measured in hours instead of days. The reason they’re able to do what the rest of us can only dream of is that these athletes can produce enormous amounts of power. Power is the rate at which cyclists burn energy and the energy they burn comes from the food they eat. And over the course of the Tour de France, the winning cyclist will burn the equivalent of roughly 210 Big Macs.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/S4O5voOCqAQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Cycling is a game of watts</h2>
<p>To make a bicycle move, a Tour de France rider transfers energy from his muscles, through the bicycle and to the wheels that push back on the ground. The faster a rider can put out energy, the greater the power. This rate of energy transfer is often measured in watts. Tour de France cyclists are capable of generating enormous amounts of power for incredibly long periods of time compared to most people.</p>
<p>For about 20 minutes, a fit recreational cyclist can consistently put out <a href="https://www.roadbikerider.com/average-wattage-cycling/">250 watts to 300 watts</a>. Tour de France cyclists can produce <a href="https://www.bicycling.com/racing/a20041587/cool-things-we-learned-from-tour-de-france-strava-files/">over 400 watts for the same time period</a>. These pros are even capable of <a href="https://www.cyclist.co.uk/in-depth/539/how-much-better-are-pro-cyclists">hitting 1,000 watts</a> for short bursts of time on a steep uphill – <a href="https://www.dailymotion.com/video/x6l981y">roughly enough power</a> to run a <a href="https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)">microwave oven</a>.</p>
<p>But not all of the energy a Tour de France cyclist puts into his bike gets turned into forward motion. Cyclists battle air resistance and frictional losses between their wheels and the road. They get help from gravity on downhills but they have to fight gravity while climbing. </p>
<p>I incorporate all of the physics associated with cyclist power output as well as the effects of gravity, air resistance and friction <a href="http://johnericgoff.blogspot.com/">into my model</a>. Using all that, I estimate that a typical Tour de France winner needs to put out an average of about 325 watts over the roughly 80 hours of the race. Recall that most recreational cyclists would be happy if they could produce 300 watts for just 20 minutes!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pile of hamburgers." src="https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Racers in the Tour de France need to eat three to four times as many calories as a person does normally.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-stack-against-black-background-royalty-free-image/1208752640?adppopup=true">Pietro Agliata/EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<h2>Turning food into miles</h2>
<p>So where do these cyclists get all this energy from? Food, of course! </p>
<p>But your muscles, like any machine, can’t convert 100% of food energy directly into energy output – muscles can be anywhere between <a href="https://www.pearson.ch/HigherEducation/Pearson/EAN/9780139228162/Mechanics-Heat-and-the-Human-Body">2% efficient when used for activities like swimming and 40% efficient in the heart</a>. In my model, I use an average efficiency of 20%. Knowing this efficiency as well as the energy output needed to win the Tour de France, I can then estimate how much food the winning cyclist needs.</p>
<p>Top Tour de France cyclists who complete all 21 stages burn about 120,000 calories during the race – or an average of nearly 6,000 calories per stage. On some of the more difficult mountain stages – like this year’s Stage 12 – racers will burn close to 8,000 calories. To make up for these huge energy losses, riders eat delectable treats such as <a href="https://www.cyclingweekly.com/news/racing/tour-de-france/this-is-what-you-have-to-eat-to-compete-in-the-tour-de-france-182775">jam rolls, energy bars and mouthwatering “jels” so they don’t waste energy chewing</a>. </p>
<p>Tadej Pogačar won both the 2021 and 2020 Tour de France and <a href="https://www.procyclingstats.com/rider/tadej-pogacar">weighs only 146 pounds</a> (66 kilograms). Tour de France cyclists don’t have much fat to burn for energy. They have to keep putting food energy into their bodies so they can put out energy at what seems like a superhuman rate. So this year, while watching a stage of the Tour de France, note how many times the cyclists eat – now you know the reason for all that snacking.</p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p>
<p><em>This is an updated version of a story originally published on June 24, 2021.</em></p><img src="https://counter.theconversation.com/content/186097/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Eric Goff does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Riders in the 2022 Tour de France will ride more than 2,100 miles (3,400 km) over the 21 flat and mountainous stages of the race. And they will burn an incredible amount of energy while doing so.John Eric Goff, Professor of Physics, University of LynchburgLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1835002022-06-10T14:54:13Z2022-06-10T14:54:13ZIs intermittent fasting actually good for weight loss? Here’s what the evidence says<figure><img src="https://images.theconversation.com/files/468199/original/file-20220610-16487-pgezi3.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6912%2C4611&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many people find intermittent fasting to be more flexible and easy to follow than other diets.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/204-fasting-diet-concept-one-third-1594385533">Marcin Malicki/ Shutterstock</a></span></figcaption></figure><p>If you’re someone who’s thought about losing weight or has wanted to get healthier in the past few years, you’ve probably come across these two words: intermittent fasting. From celebrities to fitness enthusiasts, intermittent fasting has many thousands of loyal advocates online, claiming this way of eating has helped them lose weight better than other diet methods have.</p>
<hr>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/is-intermittent-fasting-actually-good-for-weight-loss-heres-what-the-evidence-says-183500&bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/us/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<p>It’s easy to see the appeal of intermittent fasting as a weight loss method. Not only is it simple, it’s also flexible, can be adapted easily to every person, and doesn’t require you to eliminate foods or count calories. But despite its popularity, intermittent fasting may not actually be better than other diet methods when it comes to weight loss.</p>
<p>To date, numerous studies have shown intermittent fasting is as good as counting calories when it comes to weight loss – including a <a href="https://www.nejm.org/doi/full/10.1056/NEJMoa2114833">recent study</a>, which tracked participants for more than a year. </p>
<p>This has even been shown with many different types of intermittent fasting, including <a href="https://pubmed.ncbi.nlm.nih.gov/28459931/">alternate-day fasting</a> (where you fast or restrict calories every other day), <a href="https://pubmed.ncbi.nlm.nih.gov/30475957/">5:2 dieting</a> (eating normally five days a week, then fasting or restricting calories for two days) and <a href="https://www.nejm.org/doi/full/10.1056/NEJMoa2114833">time-restricted eating</a> (where you eat all of your days calories within a set time window, such as only eating during an eight hour window, then fasting for 16 hours). But no studies have yet shown intermittent fasting to be any better than conventional diets. </p>
<p>Intermittent fasting <a href="https://academic.oup.com/ajcn/article/104/6/1545/4564664">reduces the amount you eat</a>, but it may have a downside. It both reduces the amount of <a href="https://pubmed.ncbi.nlm.nih.gov/24898233/">physical activity we do</a>, and <a href="https://pubmed.ncbi.nlm.nih.gov/25970668/">reduces how hard we push during exercise</a>. </p>
<p>This is true <a href="https://pubmed.ncbi.nlm.nih.gov/32348797/">regardless of the type</a> of intermittent <a href="https://pubmed.ncbi.nlm.nih.gov/34135111/">fasting you do</a>. This suggests that when calorie intake is substantially reduced – even for a short period of time – the body adapts by reducing the number of calories used during exercise. Researchers aren’t entirely sure why this happens, however.</p>
<p>While this may not necessarily affect weight loss, lower physical activity levels can have other negative effects on health. For example, a recent <a href="https://pubmed.ncbi.nlm.nih.gov/34135111/">alternate-day fasting study</a> found that even just three weeks of this diet reduced physical activity levels and led to a greater loss of muscle mass than a daily calorie restriction diet. The fasting diet was also less effective than daily calorie restriction for fat loss.</p>
<figure class="align-center ">
<img alt="A woman in the gym performs a lat pulldown. A man behind her is using a machine to perform a chest press." src="https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/468201/original/file-20220610-20-5dnvek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Resistance training (such as weight lifting) may help prevent muscle loss from intermittent fasting.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/fitness-asian-woman-working-out-shoulder-599406365">Maridav/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Muscle mass is crucial for many reasons, including <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3716256/">regulating blood sugar levels</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/18615231/">staying physically able</a> as we get older. So diets that cause muscle loss are best avoided. However, combining intermittent fasting with exercise programmes – <a href="https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-016-1044-0">such as resistance training</a> – may help people better maintain lean muscle mass while encouraging fat loss.</p>
<h2>Are there other benefits to fasting?</h2>
<p>While intermittent fasting might not be a miracle solution when it comes to weight loss, that doesn’t mean it might not still have other health benefits.</p>
<p>A <a href="https://www.nature.com/articles/s41574-022-00638-x">recent review</a> on intermittent fasting found that it improved blood pressure, insulin sensitivity (how effectively the body regulates blood sugar) and lowered cholesterol levels to a similar extent as daily calorie restriction. </p>
<p>It is likely this effect is due to weight loss. But since few studies have followed participants for longer than a year, it’s hard to know whether the these effects persist. </p>
<p>Some research also suggests how you fast may also be key. A number of studies have shown promising results from <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/nbu.12467">early time-restricted eating</a>, which involves eating all your day’s calories in the early part of the day and fasting in the evening, usually from 4pm onwards. Eating early in the day aligns food intake with our natural circadian rhythms, which means nutrients are processed more efficiently. </p>
<p>Early time-restricted eating has also been shown to improve several markers of health, such as insulin sensitivity, which is a key risk factor for type 2 diabetes. These improvements were even seen <a href="https://pubmed.ncbi.nlm.nih.gov/29754952/">without weight loss</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-body-weight-affected-by-when-you-eat-heres-what-science-knows-so-far-143303">Is body weight affected by when you eat? Here's what science knows so far</a>
</strong>
</em>
</p>
<hr>
<p>There’s also evidence that outcomes from the 5:2 intermittent fasting diet can be improved by positioning the two very-low or no calorie diet days consecutively. This may lead to improvements in insulin sensitivity greater than what would be seen when practising <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017674/">daily calorie restriction</a>. </p>
<p>This might be due to spending more time in a fasted-state, which increases the amount of body fat you burn. Interestingly, exercising while fasting may also help you burn more fat and <a href="https://pubmed.ncbi.nlm.nih.gov/31628477/">improve insulin sensitivity</a>. </p>
<p>So while intermittent fasting might not be better than other diets for weight loss, making changes to how you do it – such as fasting in the evening – may help you see other health benefits. </p>
<p>For people who struggle to stick with calorie restriction diets, intermittent fasting is safe and may still be effective. It’s also worth noting that it’s best to combine intermittent fasting with exercise to experience the best results.</p><img src="https://counter.theconversation.com/content/183500/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Clayton has received research funding from the British Nutrition Foundation and The Society for Endocrinology.</span></em></p>Most research shows intermittent fasting to be no better for weight loss than counting calories.David Clayton, Senior Lecturer in Nutrition and Exercise Physiology, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1658672022-03-01T13:37:54Z2022-03-01T13:37:54ZWhat you eat can reprogram your genes – an expert explains the emerging science of nutrigenomics<figure><img src="https://images.theconversation.com/files/442404/original/file-20220124-23298-1b8yqek.jpg?ixlib=rb-1.1.0&rect=51%2C0%2C5700%2C3754&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Along with calories and nutrients, food can influence the genetic blueprints that shape who you are.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/cropped-image-of-hands-preparing-food-on-table-royalty-free-image/664647131?adppopup=true">Maskot via Getty Images</a></span></figcaption></figure><p><a href="https://theconversation.com/lo-que-usted-come-puede-reprogramar-sus-genes-un-experto-explica-la-ciencia-emergente-de-la-nutrigenomica-202423">Leer en español.</a> </p>
<p>People typically think of food as calories, energy and sustenance. However, the latest evidence suggests that food also “talks” to our genome, which is the genetic blueprint that directs the way the body functions down to the cellular level. </p>
<p>This communication between food and genes may affect your <a href="https://doi.org/10.1016/j.tibs.2020.04.002">health, physiology and longevity</a>. The idea that food delivers important messages to an animal’s genome is the focus of a field known as <a href="https://www.cancer.gov/publications/dictionaries/cancer-terms/def/nutrigenomics">nutrigenomics</a>. This is a discipline still in its infancy, and many questions remain cloaked in mystery. Yet already, we researchers have learned a great deal about how <a href="https://doi.org/10.1016/j.tibs.2020.04.002">food components affect the genome</a>.</p>
<p>I am a <a href="https://sites.lsa.umich.edu/dus-lab/">molecular biologist</a> who <a href="https://scholar.google.com/citations?user=MbZxwzMAAAAJ&hl=en">researches the interactions</a> <a href="https://doi.org/10.1016/j.tem.2020.11.011">among food</a>, <a href="https://doi.org/10.1016/j.neuint.2021.105099">genes</a> and <a href="https://doi.org/10.3389/fnbeh.2021.746299">brains</a> in the effort to better understand how food messages affect our biology. The efforts of scientists to decipher this transmission of information could one day result in healthier and happier lives for all of us. But until then, nutrigenomics has unmasked at least one important fact: Our <a href="https://www.youtube.com/watch?v=FmKPgBoCgKU">relationship with food is far more intimate</a> than we ever imagined. </p>
<h2>The interaction of food and genes</h2>
<p>If the idea that food can drive biological processes by interacting with the genome sounds astonishing, one need look no further than a beehive to find a proven and perfect example of how this happens. Worker bees labor nonstop, are sterile and live only a few weeks. The queen bee, sitting deep inside the hive, has a life span that lasts for years and a fecundity so potent she gives birth to an entire colony. </p>
<p>And yet, worker and queen bees are genetically identical organisms. They become two different life forms because of the <a href="https://doi.org/10.1126/science.1153069">food they eat</a>. The queen bee feasts on <a href="https://doi.org/10.1038/nature10093">royal jelly</a>; worker bees feed on nectar and pollen. Both foods provide energy, but royal jelly has an extra feature: <a href="https://doi.org/10.1038/embor.2011.9">its nutrients can unlock the genetic instructions</a> to create the anatomy and physiology of a queen bee. </p>
<p>So how is food translated into biological instructions? Remember that <a href="https://doi.org/10.1016/j.tibs.2020.04.002">food is composed of macronutrients</a>. These include carbohydrates – or sugars – proteins and fat. Food also contains micronutrients such as vitamins and minerals. These compounds and their breakdown products can trigger <a href="https://doi.org/10.1016/j.tem.2020.11.011">genetic switches that reside in the genome</a>. </p>
<figure class="align-center ">
<img alt="Two shopping carts lined up, one filled with fruits and vegetables, the other with sweets and high-fat foods." src="https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444859/original/file-20220207-25-1ick4pa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The field of nutrigenomics aims to decipher how different types of foods transmit different – and important – messages to our cells.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/healthy-vs-unhealthy-shopping-trolleys-royalty-free-image/108821364?adppopup=true">Peter Dazeley/The Image Bank via Getty Images</a></span>
</figcaption>
</figure>
<p>Like the switches that control the intensity of the light in your house, genetic switches determine how much of a certain gene product is produced. Royal jelly, for instance, contains compounds that <a href="https://doi.org/10.1038/embor.2011.9">activate genetic controllers</a> to form the queen’s organs and sustain her reproductive ability. In humans and mice, byproducts of the amino acid methionine, which are abundant in meat and fish, are known to influence genetic dials that are <a href="https://doi.org/10.1016/j.tibs.2020.04.002">important for cell growth and division</a>. And vitamin C plays a role in keeping us healthy by <a href="https://doi.org/10.3389/fgene.2021.675780">protecting the genome from oxidative damage</a>; it also promotes the function of cellular pathways that can repair the genome if it does get damaged.</p>
<p>Depending on the type of nutritional information, the genetic controls activated and the cell that receives them, the messages in food can influence <a href="https://doi.org/10.1038/nrm4048">wellness, disease risk and even life span</a>. But it’s important to note that to date, most of these studies have been conducted in animal models, like bees. </p>
<p>Interestingly, the ability of nutrients to alter the flow of genetic information can span across generations. Studies show that in humans and animals, <a href="http://dx.doi.org/10.1136/jmedgenet-2014-102577">the diet of grandparents</a> influences the activity of genetic switches and the disease risk and mortality of grandchildren. </p>
<h2>Cause and effect</h2>
<p>One interesting aspect of thinking of food as a type of biological information is that it gives new meaning to the idea of a food chain. Indeed, if our bodies are influenced by what we have eaten – down to a molecular level – then what the food we consume “ate” also could affect our genome. For example, compared to milk from grass-fed cows, the milk from grain-fed cattle has different amounts and types of <a href="https://doi.org/10.1186/1475-2891-9-10">fatty acids and vitamins C and A </a>. So when humans drink these different types of milk, their cells also receive different nutritional messages. </p>
<p>Similarly, a human mother’s diet changes the levels of fatty acids as well as vitamins such as B-6, B-12 and folate that are found in her breast milk. This could alter the type of nutritional messages reaching the baby’s own genetic switches, although whether or not this has an effect on the child’s development is, at the moment, unknown. </p>
<figure class="align-center ">
<img alt="A smiling young girl drinking a glass of milk through a straw." src="https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444867/original/file-20220207-69470-1qxu7h7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Food information derived from animals – such as cow’s milk – is transferred to the person drinking the milk.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/girl-drinking-milk-royalty-free-image/75939350?adppopup=true">Image Source/DigitalVision via Getty Images</a></span>
</figcaption>
</figure>
<p>And, maybe unbeknownst to us, we too are part of this food chain. The food we eat doesn’t tinker with just the genetic switches in our cells, but also with those of <a href="https://doi.org/10.1126/science.1223813">the microorganisms living in our guts, skin and mucosa</a>. One striking example: In mice, the breakdown of short-chain fatty acids by gut bacteria <a href="https://doi.org/10.1096/fj.14-259598">alters the levels of serotonin</a>, a brain chemical messenger that regulates mood, anxiety and depression, among other processes.</p>
<h2>Food additives and packaging</h2>
<p>Added ingredients in food can also alter the flow of genetic information inside cells. Breads and cereals <a href="https://doi.org/10.3945/an.114.007443">are enriched with folate</a> to prevent birth defects caused by deficiencies of this nutrient. But some scientists hypothesize that high levels of folate <a href="https://doi.org/10.1093/ajcn/87.3.517">in the absence of other naturally occurring micronutrients</a> such as vitamin B-12 could contribute to the higher incidence of colon cancer in Western countries, possibly by affecting the <a href="https://doi.org/10.1093/ajcn/nqaa259">genetic pathways that control growth</a>. </p>
<p>This could also be true with chemicals found in food packaging. Bisphenol A, or BPA, a compound found in plastic, <a href="https://doi.org/10.1016/j.bbi.2011.02.005">turns on genetic dials</a> in mammals that are critical to development, <a href="https://doi.org/10.3390/ijms21165761">growth and fertility</a>. For example, some researchers suspect that, <a href="https://doi.org/10.1111/1541-4337.12388">in both humans and animal models</a>, BPA influences the age of sexual differentiation and decreases fertility by making genetic switches more likely to turn on.</p>
<p>All of these examples point to the possibility that the genetic information in food could arise not just from its molecular composition – the amino acids, vitamins and the like – but also from the agricultural, environmental and economic policies of a country, or the lack of them.</p>
<p>Scientists have only recently begun decoding these genetic food messages and their role in health and disease. We researchers still don’t know precisely how nutrients act on genetic switches, what their rules of communication are and how the diets of past generations influence their progeny. Many of these studies have so far been done only in animal models, and much remains to be worked out about what the interactions between food and genes mean for humans. </p>
<p>What is clear though, is that unraveling the mysteries of nutrigenomics is likely to empower both present and future societies and generations.</p><img src="https://counter.theconversation.com/content/165867/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Dus receives funding from the National Science Foundation, the National Institute of Health, the Sloan Foundation, the Rita Allen Foundation, and the Klingenstein Foundation. She is affiliated with The University of Michigan, Ann Arbor. She is on the Advisory Board for the Trends in Endocrinology & Metabolism journal, the Editorial Board for the Chemical Senses journal, and the Advisory Board for the University of Michigan Museum of Natural History.</span></em></p>Scientists are just beginning to decode the genetic messages in your food – and how that may affect your health.Monica Dus, Associate Professor of Molecular, Cellular, and Developmental Biology, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1731972022-01-05T20:01:54Z2022-01-05T20:01:54ZA taste for sweet – an anthropologist explains the evolutionary origins of why you’re programmed to love sugar<figure><img src="https://images.theconversation.com/files/438857/original/file-20211222-48250-15eo0z2.jpg?ixlib=rb-1.1.0&rect=724%2C155%2C4914%2C3466&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Being able to perceive sweetness can guide foragers to the most calorie-rich picks.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-child-picking-blackberries-royalty-free-image/582364588">Elva Etienne/Moment via Getty Images</a></span></figcaption></figure><p>The sweetness of sugar is one of life’s great pleasures. People’s love for sweet is so visceral, food companies lure consumers to their products by adding sugar to almost everything they make: yogurt, ketchup, fruit snacks, breakfast cereals and even supposed health foods like granola bars.</p>
<p>Schoolchildren learn as early as kindergarten that sweet treats belong in the smallest tip of the food pyramid, and adults learn from the media about <a href="https://doi.org/10.3390/nu8110697">sugar’s role in unwanted weight gain</a>. It’s hard to imagine a greater disconnect between a powerful attraction to something and a rational disdain for it. How did people end up in this predicament?</p>
<p><a href="https://scholar.google.com/citations?user=zhY22GQAAAAJ&hl=en&oi=ao">I’m an anthropologist</a> who studies the evolution of taste perception. I believe insights into our species’ evolutionary history can provide important clues about why it’s so hard to say no to sweet.</p>
<h2>Sweet taste detection</h2>
<p>A fundamental challenge for our ancient ancestors was getting enough to eat.</p>
<p>The basic activities of day-to-day life, such as raising the young, finding shelter and <a href="https://doi.org/10.1086/jar.40.4.3629795">securing enough food</a>, <a href="https://www.nationalgeographic.com/foodfeatures/evolution-of-diet/">all required energy in the form of calories</a>. Individuals more proficient at garnering calories tended to be more successful at all these tasks. They survived longer and had more surviving children – they had greater fitness, in evolutionary terms.</p>
<p>One contributor to success was how good they were at foraging. Being able to detect sweet things – sugars – could give someone a big leg up.</p>
<p>In nature, sweetness signals the presence of sugars, an excellent source of calories. So foragers able to perceive sweetness could detect whether sugar was present in potential foods, especially plants, and how much.</p>
<p>This ability allowed them to assess calorie content with a quick taste before investing a lot of effort in gathering, processing and eating the items. Detecting sweetness helped early humans gather plenty of calories with less effort. Rather than browsing randomly, they could target their efforts, improving their evolutionary success. </p>
<h2>Sweet taste genes</h2>
<p>Evidence of sugar detection’s vital importance can be found at the most fundamental level of biology, the gene. Your ability to perceive sweetness isn’t incidental; it is etched in your body’s genetic blueprints. Here’s how this sense works.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Microscopic view of cells just beneath tongue's surface." src="https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Microscopic cross section of the tongue’s surface. Taste buds are clusters of cells embedded beneath the tongue’s surface, facing into the mouth through a small pore (top). Here, the taste bud is the round cluster of cells at center.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/shows-a-single-taste-bud-with-a-taste-pore-facing-royalty-free-image/139826481">Ed Reschke/Stone via Getty Images</a></span>
</figcaption>
</figure>
<p><a href="https://www.scientificamerican.com/article/making-sense-of-taste-2006-09/">Sweet perception</a> <a href="https://doi.org/10.1038/nrn.2017.68">begins in taste buds</a>, clusters of cells nestled barely beneath the surface of the tongue. They’re exposed to the inside of the mouth via small openings called taste pores.</p>
<p>Different subtypes of cells within taste buds are each responsive to a particular taste quality: sour, salty, savory, bitter or sweet. The subtypes produce receptor proteins corresponding to their taste qualities, which sense the chemical makeup of foods as they pass by in the mouth.</p>
<p>One subtype produces bitter receptor proteins, which respond to toxic substances. Another produces savory (also called umami) receptor proteins, which sense amino acids, the building blocks of proteins. <a href="https://doi.org/10.1007/s12031-020-01642-4">Sweet-detecting cells produce a receptor protein</a> called TAS1R2/3, which <a href="https://sitn.hms.harvard.edu/flash/2013/the-bittersweet-truth-of-sweet-and-bitter-taste-receptors/">detects sugars</a>. When it does, it sends a neural signal to the brain for processing. This message is how you perceive the sweetness in a food you’ve eaten.</p>
<p>Genes encode the instructions for how to make every protein in the body. The sugar-detecting receptor protein TAS1R2/3 is encoded by a pair of genes on chromosome 1 of the human genome, conveniently named TAS1R2 and TAS1R3.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="black bat hangs upside down from branch, holding fruit" src="https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A fruit bat enjoys a sweet treat.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/one-fiji-flying-fox-isolated-on-white-background-copy-space-news-photo/1095489104">Avalon/Universal Images Group via Getty Images</a></span>
</figcaption>
</figure>
<p>Comparisons with other species reveal just how deeply sweet perception is embedded in human beings. The TAS1R2 and TAS1R3 genes <a href="https://www.discovermagazine.com/planet-earth/accounting-for-taste-why-a-bear-but-not-a-seal-will-steal-your-cupcake">aren’t only found in humans</a> – <a href="https://doi.org/10.1007/s11434-013-5811-5">most other vertebrates have them, too</a>. They’re found in monkeys, cattle, rodents, dogs, bats, lizards, pandas, fish and myriad other animals. The two genes have been in place for hundreds of millions of years of evolution, ready for the first human species to inherit.</p>
<p>Geneticists have long known that genes with important functions are kept intact by natural selection, while genes without a vital job tend to decay and sometimes disappear completely as species evolve. Scientists think about this as the use-it-or-lose-it theory of evolutionary genetics. The presence of the TAS1R1 and TAS2R2 genes across so many species testifies to the advantages sweet taste has provided for eons.</p>
<p>The use-it-or-lose-it theory also explains the remarkable discovery that animal species that don’t encounter sugars in their typical diets have <a href="https://doi.org/10.1073/pnas.1118360109">lost their ability to perceive it</a>. For example, many carnivores, who benefit little from perceiving sugars, harbor only broken-down relics of TAS1R2.</p>
<h2>Sweet taste liking</h2>
<p>The body’s sensory systems detect myriad aspects of the environment, from light to heat to smell, but we aren’t attracted to all of them the way we are to sweetness.</p>
<p>A perfect example is another taste, bitterness. Unlike sweet receptors, which detect desirable substances in foods, bitter receptors detect undesirable ones: toxins. And the brain responds appropriately. While sweet taste tells you to keep eating, bitter taste tells you to spit things out. This makes evolutionary sense. </p>
<p>So while your tongue detects tastes, it is your brain that decides how you should respond. If responses to a particular sensation are consistently advantageous across generations, <a href="https://doi.org/10.1016/j.cub.2017.11.016">natural selection fixes them in place</a> and <a href="https://doi.org/10.1038/007417a0">they become instincts</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/r2aMf3oTxss?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Even newborns have a preference for sweet and an aversion to bitter.</span></figcaption>
</figure>
<p>Such is the case with bitter taste. Newborns don’t need to be taught to dislike bitterness – they reject it instinctively. The opposite holds for sugars. Experiment after experiment finds the same thing: <a href="https://doi.org/10.1097/MCO.0b013e328346df65">People are attracted to sugar from the moment they’re born</a>. These responses can be shaped by later learning, but they <a href="https://www.npr.org/sections/thesalt/2014/03/19/291406696/why-a-sweet-tooth-may-have-been-an-evolutionary-advantage-for-kids">remain at the core of human behavior</a>.</p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://memberservices.theconversation.com/newsletters/?nl=science&source=inline-science-best">Sign up for The Conversation’s science newsletter</a>.]</p>
<h2>Sweetness in humans’ future</h2>
<p>Anyone who decides they want to reduce their sugar consumption is up against millions of years of evolutionary pressure to find and consume it. People in the developed world now live in an environment where society produces more sweet, refined sugars than can possibly be eaten. There is a destructive mismatch between the evolved drive to consume sugar, current access to it and the human body’s responses to it. In a way, we are victims of our own success.</p>
<p>The attraction to sweetness is so relentless that <a href="https://doi.org/10.3389/fpsyt.2018.00545">it has been called an addiction</a> comparable to nicotine dependence – itself notoriously difficult to overcome.</p>
<p>I believe it is worse than that. From a physiological standpoint, nicotine is an unwanted outsider to our bodies. People desire it because it plays tricks on the brain. In contrast, the desire for sugar has been in place and genetically encoded for eons because it provided fundamental fitness advantages, the ultimate evolutionary currency.</p>
<p>Sugar isn’t tricking you; you are responding precisely as programmed by natural selection.</p>
<p></p><hr> <p></p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em>This article is part of a series examining sugar’s effects on human health and culture. <a href="https://theconversation.com/us/topics/sugar-2022-114641">You can read the articles on theconversation.com.</a></em></p><img src="https://counter.theconversation.com/content/173197/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Wooding does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you ever feel like you can’t stop eating sugar, you are responding precisely as programmed by natural selection. What was once an evolutionary advantage has a different effect today.Stephen Wooding, Assistant Professor of Anthropology and Heritage Studies, University of California, MercedLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1725712022-01-05T13:45:41Z2022-01-05T13:45:41ZWhat’s the difference between sugar, other natural sweeteners and artificial sweeteners? A food chemist explains sweet science<figure><img src="https://images.theconversation.com/files/438548/original/file-20211220-15-4utuse.jpg?ixlib=rb-1.1.0&rect=349%2C445%2C4427%2C2663&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sugar is just one of many flavor enhancers people and companies use to sweeten foods and beverages.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/food-service-tray-with-sugar-packets-salt-and-royalty-free-image/1000353706?adppopup=true">Marie LaFauci/Moment via Getty Images</a></span></figcaption></figure><p>A quick walk down the drink aisle of any corner store reveals the incredible ingenuity of food scientists in search of sweet flavors. In some drinks you’ll find sugar. A diet soda might have an artificial or natural low-calorie sweetener. And found in nearly everything else is high fructose corn syrup, the king of U.S. sweetness.</p>
<p>I am a <a href="https://chemistry.richmond.edu/faculty/knolin/">chemist who studies compounds found in nature</a>, and I am also a lover of food. With confusing food labels claiming foods and beverages to be diet, zero-sugar or with “no artificial sweeteners,” it can be confusing to know exactly what you are consuming.</p>
<p>So what are these sweet molecules? How can cane sugar and artificial sweeteners produce such similar flavors? First, it is helpful to understand how taste buds work.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two girls licking lollipops." src="https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438556/original/file-20211220-50043-nhxa2s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">You perceive sweet flavors when certain molecules bind to the taste buds on your tongue.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/two-girls-eating-lollipops-outdoors-royalty-free-image/724286183?adppopup=true">Bomin Jeong/EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<h2>Taste buds and chemistry</h2>
<p>The “<a href="https://theconversation.com/that-neat-and-tidy-map-of-tastes-on-the-tongue-you-learned-in-school-is-all-wrong-44217">taste map</a>” – the idea that you taste different flavors on different parts of your tongue – is far from the truth. People are able to taste all flavors anywhere there are taste buds. So what’s a taste bud?</p>
<p>Taste buds are areas on your tongue that contain dozens of taste <a href="http://www.vivo.colostate.edu/hbooks/pathphys/digestion/pregastric/taste.html">receptor cells</a>. These cells can detect the five flavors – sweet, sour, salty, bitter and umami. When you eat, food molecules are dissolved in saliva and then washed across the taste buds, where they bind to the different taste receptor cells. Only molecules with certain shapes can bind to certain receptors, and this produces the perception of different flavors. </p>
<p>Molecules that taste sweet bind to specific proteins on the taste receptor cells called <a href="https://teachmephysiology.com/biochemistry/molecules-and-signalling/g-protein/">G-proteins</a>. When a molecule binds these G-proteins, it triggers a series of signals that are sent to the brain where it is interpreted as sweet. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram of a glucose molucule." src="https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=649&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=649&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=649&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=815&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=815&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438560/original/file-20211220-23354-1etdb6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=815&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Glucose is the simplest of sugars and is a circle of carbon atoms with oxygen and hydrogen atoms attached to the ring.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Alpha-D-Glucopyranose.svg#/media/File:Alpha-D-Glucopyranose.svg">NEUROtiker/WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>Natural sugars</h2>
<p>Natural sugars are types of carbohydrates known as <a href="https://www.biologyonline.com/dictionary/saccharide">saccharides</a> that are made of carbon, oxygen and hydrogen. You can imagine sugars as rings of carbon atoms with pairs of oxygen and hydrogen attached to the outside of the rings. The oxygen and hydrogen groups are what make sugar sticky to the touch. They behave like Velcro, sticking to the oxygen and hydrogen pairs on other sugar molecules.</p>
<p>The simplest sugars are single-molecule sugars called monosaccharides. You’ve probably heard of some of these. Glucose is the most basic sugar and is mostly made by plants. <a href="https://foodinsight.org/what-is-fructose/">Fructose</a> is a sugar from fruit. <a href="https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Supplemental_Modules_(Biological_Chemistry)/Carbohydrates/Monosaccharides/Galactose">Galactose</a> is a sugar in milk. </p>
<p>Table sugar – or <a href="https://www.sugar.org/sugar/what-is-sugar/">sucrose</a>, which comes from sugar cane – is an example of a dissacharide, a compound made of two <a href="https://www.biologyonline.com/dictionary/monosaccharide">monosaccharides</a>. Sucrose is formed when a <a href="https://sphweb.bumc.bu.edu/otlt/mph-modules/ph/ph709_basiccellbiology/PH709_BasicCellBIology3.html">glucose molecule</a> and a <a href="https://sphweb.bumc.bu.edu/otlt/mph-modules/ph/ph709_basiccellbiology/PH709_BasicCellBIology3.html">fructose molecule</a> join together. Other common dissacharides are lactose from milk and maltose, which comes grains.</p>
<p>When these sugars are eaten, the body processes each of them slightly differently. But eventually they are broken down into molecules that your body converts into energy. The amount of energy from sugar – and all food – is measured in calories.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aisle of soda." src="https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438557/original/file-20211220-15-88xiit.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">High fructose corn syrup is the main sweetener for many processed foods and drinks.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/sanibel-island-jerrys-foods-grocery-store-soda-aisle-news-photo/1189380097?adppopup=true">Jeff Greenberg/Universal Images Group via Getty Images</a></span>
</figcaption>
</figure>
<h2>High fructose corn syrup</h2>
<p>High fructose corn syrup is a staple of U.S. foods, and this hybrid sugar sweetener needs a category all on its own. <a href="https://foodinsight.org/what-is-high-fructose-corn-syrup/">High fructose corn syrup</a> is made from corn starch – the main carbohydrate found in corn. Corn starch is made of <a href="http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/polysac.html">thousands of glucose molecules</a> bonded together. At an industrial scale, the starch is broken into individual glucose molecules using <a href="https://www.fda.gov/food/food-additives-petitions/high-fructose-corn-syrup-questions-and-answers">enzymes</a>. This glucose is then treated with a second enzyme to convert some of it into fructose. Generally, high fructose corn syrup is roughly <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/high-fructose-corn-syrup">42%-55% fructose</a>.</p>
<p>This blend is sweet and cheap to produce but has a high calorie content. As with other natural sugars, <a href="https://theconversation.com/sugar-isnt-just-empty-fattening-calories-its-making-us-sick-49788">too much high fructose corn syrup is bad for your health</a>. And since most processed foods and drinks are packed full of the stuff, it is easy to consume too much. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small green plant in a pot." src="https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=790&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=790&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=790&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=993&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=993&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438561/original/file-20211220-23354-o8hpsb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=993&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A chemical in the stevia plant also produces sweet flavors.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Stevia_rebaudiana_(potted_plant).jpg#/media/File:Stevia_rebaudiana_(potted_plant).jpg">Gabriela F. Ruellan/WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>Natural nonsugar sweeteners</h2>
<p>The second category of sweeteners could be defined as natural nonsugar sweeteners. These are food additives such as stevia and monk fruit, as well as natural sugar alcohols. These molecules aren’t sugars, but they can still bind to the sweet receptors and therefore taste sweet.</p>
<p><a href="https://dx.doi.org/10.1097%2FNT.0000000000000094">Stevia</a> is a molecule that comes from the leaves of the <em>Stevia redaudiana</em> plant. It contains “sweet” molecules that are much larger than most sugars and have three glucose molecules attached to them. These molecules are 30 to 150 times sweeter than glucose itself. The sweet molecules from monk fruit are similar to stevia and 250 times sweeter than glucose. </p>
<p>The human body has a really hard time breaking down both stevia and monk fruit. So even though they’re both really sweet, you don’t get any calories from eating them.</p>
<p><a href="https://www.ynhh.org/services/nutrition/sugar-alcohol.aspx">Sugar alcohols</a>, like sorbital, for example, are not as sweet as sucrose. They can be found in a variety of foods, including pineapples, mushrooms, carrots and seaweed, and are often added to diet drinks, sugar-free chewing gum and many other foods and drinks. Sugar alcohols are made of chains of carbon atoms instead of circles like normal sugars. While they are composed of the same atoms as the sugars, sugar alcohols are not absorbed well by the body so they are considered low-calorie sweeteners.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Packets of Splenda, Sweet'N Low and Equal." src="https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=237&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=237&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=237&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=298&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=298&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438555/original/file-20211220-50538-tkxi4f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=298&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chemists have developed a number of lab-made chemicals that taste sweet and are sold as no-sugar sweeteners.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:No-Calorie-Sweetener-Packets.jpg#/media/File:No-Calorie-Sweetener-Packets.jpg">Evan Amos/WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>Artificial sweeteners</h2>
<p>The third way to make something sweet is to add <a href="https://dx.doi.org/10.1007%2Fs13197-011-0571-1">artificial sweeteners</a>. These chemicals are produced in labs and factories and are not found in nature. Like all things that taste sweet, they do so because they can bind to certain receptors in taste buds. </p>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.] </p>
<p>So far, the U.S. Food and Drug Administration has <a href="https://www.fda.gov/food/food-additives-petitions/additional-information-about-high-intensity-sweeteners-permitted-use-food-united-states">approved six artificial sweeteners</a>. The most well known are probably saccharin, aspartame and sucralose – better known as Splenda. Artificial sweeteners all have different chemical formulas. Some resemble natural sugars while others are radically different. They are usually many times sweeter than sugar – saccharin is an incredible 200 to 700 times sweeter than table sugar – and some of them are hard for the body to break down.</p>
<p>While a sweet dessert may be a simple pleasure for many, the chemistry of how your taste buds perceive sweetness is not so simple. Only molecules with the perfect combination of atoms taste sweet, but bodies deal with each of these molecules differently when it comes to calories. </p>
<p></p><hr> <p></p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em>This article is part of a series examining sugar’s effects on human health and culture. <a href="https://theconversation.com/us/topics/sugar-2022-114641">You can read the articles on theconversation.com.</a></em></p><img src="https://counter.theconversation.com/content/172571/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kristine Nolin does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Just because something is sweet doesn’t necessarily mean it is sugary. There are a number of molecules that taste sweet. To understand how and why takes a little bit of chemistry.Kristine Nolin, Associate Professor of Chemistry, University of RichmondLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1569002021-12-27T12:58:46Z2021-12-27T12:58:46ZNot all calories are equal – a dietitian explains the different ways the kinds of foods you eat matter to your body<figure><img src="https://images.theconversation.com/files/438740/original/file-20211221-27-qlzv07.jpg?ixlib=rb-1.1.0&rect=0%2C405%2C4431%2C3320&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Even if two foods share the same calorie count, there can be major differences in how they affect your body.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/healthy-and-unhealthy-food-background-from-fruits-royalty-free-image/1249589196">Julia_Sudnitskaya/iStock via Getty Images</a></span></figcaption></figure><p>A calorie is a calorie is a calorie, at least from a thermodynamic standpoint. It’s defined as the amount of energy needed to raise the temperature of 1 kilogram of water by 1 degree Celsius (2.2 pounds by 1.8 degrees Fahrenheit).</p>
<p>But when it comes to health and your body’s energy balance, not all calories are equal.</p>
<p>For example, <a href="https://doi.org/10.1056/NEJMoa022207">some studies have reported</a> that <a href="https://doi.org/10.1186/1743-7075-11-53">diets that are</a> <a href="https://doi.org/10.1038/sj.ijo.0800867">high-protein</a>, <a href="https://doi.org/10.1210/jc.2002-021480">low-carbohydrate</a> or a combination of the two do <a href="https://doi.org/10.1056/NEJMoa022637">yield greater weight loss</a> than diets with other levels of fat, protein and carbs.</p>
<p>If every calorie in food were the same, you wouldn’t expect to see weight-loss differences among people who eat the same number of calories that are doled out in different types of food.</p>
<p><a href="https://scholar.google.com/citations?user=nrjfStkAAAAJ&hl=en&oi=ao">Dietitians like me</a> know there are many factors that influence what a calorie means for your body. Here’s what we understand about calories and nutrition so far.</p>
<h2>Energy actually available to your body</h2>
<p>In the late 1800s, chemist W.O. Atwater and his colleagues devised a system to figure out how much energy – that is, how many calories – various foods contain. Basically, he burned up food samples and recorded how much energy they released in the form of heat.</p>
<p>Not every bit of energy in food that can combust in the lab is actually available to your body, though. What scientists call <a href="https://doi.org/10.1093/jn/124.suppl_9.1738S">metabolizable energy</a> is the difference between the total energy of the food consumed and the energy that passes out of your body, undigested, in feces and urine. For each of the three macronutrients – proteins, carbohydrates and fats – Atwater devised a percentage of the calories they contained that would actually be metabolizable.</p>
<p><iframe id="ncG8V" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/ncG8V/5/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>According to the Atwater system, one gram of each macronutrient is estimated to provide a certain number of calories. The U.S. Department of Agriculture still uses these calculations today to come up with an <a href="https://fdc.nal.usda.gov/">official calorie number</a> for every food.</p>
<h2>How much energy you use</h2>
<p>What you eat can affect what scientists call your body’s <a href="https://doi.org/10.1007/978-1-4419-1005-9_454">energy expenditure</a>. That’s how much energy it takes to keep you alive – energy you use breathing, digesting, keeping your blood flowing and so on – along with what you exert moving your body. You might have heard this <a href="https://theconversation.com/whether-slow-or-fast-heres-how-your-metabolism-influences-how-many-calories-you-burn-each-day-149231">referred to as metabolism</a>.</p>
<p>Diet quality can alter the body’s energy expenditure, which is also called the <a href="https://doi.org/10.1172/JCI112913">thermic effect of food</a>. For example, in one study, people eating the same number of calories per day but on either a low-carbohydrate diet or a low-fat diet had <a href="https://doi.org/10.1001/jama.2012.6607">differences in total energy expenditure</a> of about 300 calories per day. Those eating very low-carb diets used the most energy, while those eating low-fat diets used the least.</p>
<p>In another study, <a href="https://doi.org/10.1002/j.1550-8528.1994.tb00074.x">high-fat diets led to lower</a> total energy expenditure than high-carb diets did. Other researchers reported that although substituting carbs for fat did not alter energy expenditure, people who increased their protein intake to 30%-35% of their diet <a href="https://doi.org/10.1093/ajcn/79.5.899S">used more energy</a>.</p>
<p>In general, diets high in carbohydrates, <a href="https://doi.org/10.1038/sj.ijo.0800810">fat or both produce a 4%-8% increase</a> in energy expenditure, while meals <a href="https://doi.org/10.1038/sj.ejcn.1600578">high in protein cause an 11%-14% increase</a> above the resting metabolic rate. Protein has a higher thermic effect because it’s harder for the body to break down. Although these variations aren’t huge, they could <a href="https://doi.org/10.17925/EE.2013.09.02.111">contribute to the obesity epidemic</a> by encouraging a subtle average weight gain.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Nutrition Facts panels from multiple food packages" src="https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438736/original/file-20211221-25-1qkrnq3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nutrition Facts food labels contain much more than just calorie counts – for good reason.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/nutrition-label-giving-information-on-good-food-royalty-free-image/185262405">Imagesbybarbara/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>Quality of the calories you eat</h2>
<p>Dietitians pay attention to a <a href="https://doi.org/10.1001/jama.287.18.2414">food’s glycemic index</a> and <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/glycemic-load">glycemic load</a> – that is, how quickly and how much it will increase your blood glucose levels. A rise in blood glucose triggers the release of insulin, which in turn influences energy metabolism and storage of excess energy as fat.</p>
<p>Foods like white rice, cakes, cookies and chips are all high on the glycemic index/load. Green vegetables, raw peppers, mushrooms and legumes are all low on the glycemic index/load. There is some evidence to suggest that foods <a href="https://doi.org/10.1016/j.numecd.2013.04.008">lower on the glycemic index/load</a> may be <a href="https://doi.org/10.1001/jama.287.18.2414">better for keeping blood sugar levels regulated</a> – regardless of the calories they contain.</p>
<p>Reward centers in the brain light up when people eat high glycemic index/load foods, highlighting the <a href="https://doi.org/10.3945/ajcn.113.064113">pleasurable and addictive effect</a> of foods like candy or white breads.</p>
<p><a href="https://doi.org/10.1371/journal.pmed.1003053">The fiber content of food</a> is another thing to consider. Your body can’t digest fiber – found in plant foods like fruits, vegetables, whole grains and beans – for energy. So foods high in fiber tend to have <a href="https://doi.org/10.3945/ajcn.117.163246">less metabolizable energy</a> and can help you feel full on fewer calories.</p>
<p>Empty calories – those from foods with minimal or no nutritional value – are another factor to consider. Things like white sugar, soft drinks and many ultra-processed snacks don’t provide much, if any, benefit in the form of protein, vitamins or minerals along with their calories. The opposite would be <a href="https://www.cancer.gov/publications/dictionaries/cancer-terms/def/nutrient-dense-food">nutrient-dense foods</a> that are high in nutrients or fiber, while still being relatively low in calories. Examples are spinach, apples and beans.</p>
<p>And don’t think of empty calories as neutral. Nutritionists consider them harmful calories because they can have a negative effect on health. <a href="https://doi.org/10.1056/NEJMoa1014296">Foods that are the biggest contributors to weight gain</a> are potato chips, potatoes, sugar-sweetened beverages and meats, both processed and unprocessed. On the other hand, foods that are inversely associated with weight gain are vegetables, whole grains, fruits, nuts and yogurt.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="view from above of plates on a table where people are eating" src="https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438737/original/file-20211221-27-1rjoeti.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Food provides more than calories.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/friends-eating-together-royalty-free-image/658616918">Ridofranz/iStock via Getty Images</a></span>
</figcaption>
</figure>
<h2>More to health than calories and weight</h2>
<p>It is indisputable that for weight loss, the difference between the number of calories consumed and the number of calories exerted through exercise is the most important factor. But don’t fool yourself. While weight plays a role in health and longevity, weight loss alone doesn’t equate to health.</p>
<p>Yes, some high-protein diets seem to promote weight loss at least in the short term. But epidemiologists know that in areas where people live the longest – close to 100 years on average – they <a href="https://doi.org/10.1093/jn/131.11.3065S">eat a primarily plant-based diet</a>, with very low or no animal-based protein and low or moderate fat in the form of mono- and polyunsaturated fats.</p>
<p>I often hear friends or clients say things like “it’s those carbs that are making me fat” or “I need to go on a low-carb diet.” But these complaints drive dietitians like me, well, nuts. Carbohydrates include foods like Coca-Cola and candy canes, but also apples and spinach. Cutting down on simple carbs like soft drinks, refined-flour bakery items, pasta and sweets will definitely have a positive impact on health. But eliminating carbohydrates like vegetables and fruit will have the opposite effect.</p>
<p><a href="https://doi.org/10.1016/j.ebiom.2019.04.005">A plant-based diet</a> <a href="https://doi.org/10.1136/bmj.m2412">high in plant-based protein</a> <a href="https://doi.org/10.1016/j.cell.2015.02.020">and carbohydrates</a> mostly from vegetables, fruit, nuts and legumes is <a href="https://doi.org/10.1079/phn2004558">the healthiest diet researchers know of</a> for longevity and prevention of chronic diseases like heart disease, cancer, hypertension and many other conditions. </p>
<p>The modern Western diet suffers from an <a href="https://doi.org/10.1038/ijo.2012.225">increase in quantity of calories</a> consumed with a concurrent <a href="https://doi.org/10.3945/ajcn.114.100867">decrease in the quality of calories</a> consumed. And researchers now know that calories from different foods <a href="https://doi.org/10.1056/NEJMoa1014296">have different effects</a> on fullness, insulin response, the process of turning carbs to body fat, and metabolic energy expenditure.</p>
<p>Where your health is concerned, count more on the quality of the calories you consume than the calorie count.</p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p><img src="https://counter.theconversation.com/content/156900/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Terezie Tolar-Peterson does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>In almost every way, one cheeseburger does not equal six apples. With the goal of optimal health in mind, a calorie is not a calorie is not a calorie.Terezie Tolar-Peterson, Associate Professor of Food Science, Nutrition & Health Promotion, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1658042021-12-02T13:42:06Z2021-12-02T13:42:06ZSea otters demonstrate that there is more to muscle than just movement – it can also bring the heat<figure><img src="https://images.theconversation.com/files/432004/original/file-20211115-21-1852gim.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C3637&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sea otters are born with a supercharged metabolism.
</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/cute-sea-otter-making-a-splash-royalty-free-image/1304610196">Adria Photography/Moment via Getty Images</a></span></figcaption></figure><p>Life in the cold can be difficult for animals. As the body chills, organs including the brain and muscles slow down. </p>
<p>The body temperature of animals such as reptiles and amphibians mostly depends on the temperature of their environment – but mammals can increase their metabolism, using more energy to warm their body. This allows them to <a href="https://doi.org/10.1146/annurev.ph.57.030195.000441">live in colder areas and stay active when temperatures drop</a> at night or during winter months. </p>
<p>Although scientists know mammals can increase their metabolism in the cold, it has not been clear which organs or tissues are using this extra energy to generate more heat. Staying warm is especially challenging for small, aquatic mammals like sea otters, so we wanted to know how they have adapted to survive the cold. </p>
<p>We assembled <a href="https://scholar.google.com/citations?hl=en&user=j27jLwUAAAAJ">a</a> <a href="https://scholar.google.com/citations?hl=en&user=oWs13ikAAAAJ">research</a> <a href="https://scholar.google.com/citations?hl=en&user=-BQkMmoAAAAJ">team</a> with expertise in both human and marine mammal metabolism, including <a href="https://scholar.google.com/citations?hl=en&user=hsiWIEEAAAAJ">Heidi Pearson</a> of the University of Alaska Southeast and <a href="https://scholar.google.com/citations?hl=en&user=G3AiPisAAAAJ">Mike Murray</a> of the Monterey Bay Aquarium. Understanding energy use in animals adapted to life in the cold may also provide clues for manipulating human metabolism.</p>
<h2>Sea otter metabolism</h2>
<p>It is especially difficult for water-living mammals to stay warm because <a href="https://doi.org/10.1080/23328940.2021.1988817">water conducts heat away from the body much faster than air</a>. Most marine mammals have large bodies and a thick layer of fat or <a href="https://doi.org/10.1080/23328940.2021.1988817">blubber for insulation</a>. </p>
<p>Sea otters are the smallest of the marine mammals, and do not have this thick layer of blubber. Instead, they are insulated by the densest fur of any mammal, with as many as <a href="https://doi.org/10.1111/j.1748-7692.1992.tb00120.x">a million hairs per square inch</a>. This fur, however, is high maintenance, requiring <a href="https://www.youtube.com/watch?v=sgFMVRtkpVY&list=PLq_DVMr7CmlIb0n3DhtcU8lESsxX-wqP7&index=2">regular grooming</a>. About 10% of a sea otter’s <a href="https://doi.org/10.1242/jeb.02767">daily activity</a> involves maintaining the insulating layer of air trapped in their fur.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Z4OKk2lErwc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Grooming is a never-ending job.</span></figcaption>
</figure>
<p>Dense fur is not enough, by itself, to keep sea otters warm. To generate enough body heat, their metabolic rate at rest is <a href="https://link.springer.com/book/10.1007%2F978-3-319-98280-9">about three times higher</a> than that of most mammals of similar size. This high metabolic rate has a cost, though.</p>
<p>To obtain enough energy to fuel the high demand, sea otters must eat <a href="https://doi.org/10.1086/physzool.55.1.30158441">more than 20% of their body mass</a> in food each day. In comparison, humans eat around 2% of their body mass – about <a href="https://doi.org/10.1079/BJN19810074">3 pounds (1.3 kilograms) of food per day</a> for a 155-pound (70 kg) person.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sea otter floating on its back eating a crab." src="https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/432007/original/file-20211115-17-rlq9ul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Feeding on Dungeness crab in Monterey Bay, California.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/sea-otter-and-crab-royalty-free-image/1209955271">Chase Dekker Wild-Life Images/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>Where does the heat come from?</h2>
<p>When animals eat, the energy in their food cannot be used directly by cells to do work. Instead, the food is broken down into simple nutrients, such as fats and sugars. These nutrients are then transported in the blood and absorbed by cells. </p>
<p>Within the cell are compartments called mitochondria where nutrients are converted into <a href="https://www.nature.com/scitable/definition/atp-318/">ATP</a> – a high-energy molecule that acts as the energy currency of the cell. </p>
<p>The process of converting nutrients into ATP is similar to <a href="https://www.usgs.gov/special-topic/water-science-school/science/hydroelectric-power-how-it-works?qt-science_center_objects=0#qt-science_center_objects">how a dam turns stored water into electricity</a>. As water flows out from the dam, it makes electricity by spinning blades connected to a generator – similar to wind turning the blades on a windmill. If the dam is leaky, some water – or stored energy – is lost and cannot be used to make electricity.</p>
<p>Similarly, leaky mitochondria are less efficient at making ATP from nutrients. Although the leaked energy in the mitochondria cannot be used to do work, it generates heat to warm the sea otter’s body.</p>
<p><a href="https://doi.org/10.1152/physrev.1997.77.3.731">All tissues in the body use energy and make heat</a>, but some tissues are larger and more active than others. Muscle makes up 30% of the body mass of most mammals. When active, muscles consume a lot of energy and produce a lot of heat. You have undoubtedly experienced this, whether getting hot during exercise or <a href="https://theconversation.com/its-cold-a-physiologist-explains-how-to-keep-your-body-feeling-warm-108816">shivering when cold</a>. </p>
<p>To find out if muscle metabolism helps keep sea otters warm, we studied small muscle samples from sea otters ranging in size and age from newborn pups to adults. We placed the muscle samples in small chambers designed to monitor oxygen consumption – a measure of how much energy is used. By adding different solutions that stimulated or inhibited various metabolic processes, we determined how much energy the mitochondria could use to make ATP – and how much energy could go into heat-producing leak. </p>
<p>We discovered the mitochondria in <a href="https://doi.org/10.1126/science.abf4557">sea otter muscles could be very leaky</a>, allowing otters to turn up the heat in their muscles without physical activity or shivering. It turns out that sea otter muscle is good at being inefficient. The energy “lost” as heat while turning nutrients into movement allows them to survive the cold.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sea otter floats on her back, feeding her pup small bits of food." src="https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=516&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=516&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431999/original/file-20211115-17-1g2znp7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=516&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A mother sea otter ‘hand-feeds’ her baby bits of crab. Moro Bay, California.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/feeding-baby-dinner-royalty-free-image/582228357">PhotoviewPlus/Moment Open via Getty Images</a></span>
</figcaption>
</figure>
<p>Remarkably, we found newborn pups have the same metabolic ability as adults, even though their muscles have not yet matured for swimming and diving. </p>
<h2>Broader implications</h2>
<p>Our research clearly demonstrates that muscle is important for more than just movement. Because muscle makes up such a large portion of body mass, even a small increase in muscle metabolism can dramatically increase how much energy an animal uses. </p>
<p>[<em>More than 140,000 readers get one of The Conversation’s informative newsletters.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140K">Join the list today</a>.]</p>
<p>This has important implications for human health. If scientists discover ways to safely and reversibly increase skeletal muscle metabolism at rest, doctors could possibly use this as a tool to reduce climbing rates of obesity by increasing the amount of calories a patient can burn. Conversely, reducing skeletal muscle metabolism could conserve energy in patients suffering from cancer or other wasting diseases and could reduce food and resources needed to support astronauts on long-duration spaceflight.</p><img src="https://counter.theconversation.com/content/165804/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Randall Davis has received research funding from the National Science Foundation and NOAA.</span></em></p><p class="fine-print"><em><span>Melinda Sheffield-Moore and Traver Wright do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research finds that ‘leaky mitochondria’ help keep sea otters warm.Traver Wright, Research Assistant Professor of Health and Kinesiology, Texas A&M UniversityMelinda Sheffield-Moore, Professor of Health and Kinesiology, Texas A&M UniversityRandall Davis, Regents Professor, Department of Marine Biology, Texas A&M UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1637112021-10-21T12:46:35Z2021-10-21T12:46:35ZDecades of hype turned protein into a superfood – and spawned a multibillion-dollar industry<figure><img src="https://images.theconversation.com/files/426263/original/file-20211013-27-pl9dc1.jpg?ixlib=rb-1.1.0&rect=131%2C59%2C7817%2C5195&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A protein-rich shake is often the way many people try to get more of this nutrient into their diets.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/african-american-woman-at-home-drinking-a-smoothie-royalty-free-image/1206327568?adppopup=true">andresr E+ via Getty Images</a></span></figcaption></figure><p>Do you ever blend up a protein smoothie for breakfast, or grab a protein bar following an afternoon workout? If so, you are likely among the millions of people in search of more protein-rich diets. </p>
<p><a href="https://drinkprotein2o.com/">Protein-enriched products are ubiquitous</a>, and these days it seems protein can be infused into anything – even water. But the problem, as <a href="https://www.mayoclinichealthsystem.org/providers/kristi-wempen-rdn">Kristi Wempen</a>, a nutritionist at Mayo Clinic, <a href="https://www.mayoclinichealthsystem.org/hometown-health/speaking-of-health/are-you-getting-too-much-protein">points out</a>, is that “contrary to all the hype that everyone needs more protein, most Americans get twice as much as they need.”</p>
<p>Many of us living in the most economically developed countries are buying into a <a href="https://www.pcrm.org/good-nutrition/nutrition-information/protein">myth</a> of protein deficiency created and perpetuated by food companies and a wide array of self-identified health experts. Global retail sales of protein supplement products – usually containing a combination of whey, casein or plant-based proteins such as peas, soy or brown rice – reached a <a href="https://www.grandviewresearch.com/industry-analysis/protein-supplements-market">staggering US$18.9 billion in 2020</a>, with the U.S. making up around half of the market. </p>
<p>I am a <a href="https://www.historians.org/publications-and-directories/perspectives-on-history/september-2020/protein-territory-isolation-introducing-the-ahas-2020%E2%80%9321-fellowship-winners">food historian</a> and recently spent a month at the Library of Congress trying to answer the question of why we have historically been – and remain – so focused on dietary protein. I wanted to explore the ethical, social and cultural implications of this multibillion-dollar industry. </p>
<h2>Experts weigh in</h2>
<p>Weight-loss surgeon <a href="https://www.truehealthinitiative.org/council_member/garth-davis/">Garth Davis</a> <a href="https://harperone.com/blog/is-our-obsession-with-meat-killing-us/">writes</a> in his book “Proteinaholic” that “‘eat more protein’ may be the worst advice ‘experts’ give to the public.” Davis contends that most physicians in the U.S. have never actually examined a patient with protein deficiency because simply by eating an adequate number of daily calories we are also most likely getting enough protein. </p>
<p>In fact, Americans currently <a href="https://www.health.harvard.edu/staying-healthy/the-hidden-dangers-of-protein-powders">consume almost two times</a> the National Academy of Medicine’s recommended daily intake of protein: 56 grams for men and 46 grams for women – the equivalent of two eggs, a half-cup of nuts and 3 ounces of meat – although optimal protein intake may vary depending on age and activity level. </p>
<p>For example, if you’re a dedicated athlete you might need to consume higher quantities of protein. Generally, though, <a href="https://www.health.harvard.edu/nutrition/when-it-comes-to-protein-how-much-is-too-much">a 140-pound person should not exceed 120 grams of protein per day</a>, particularly because a high protein diet can <a href="https://pubmed.ncbi.nlm.nih.gov/32669325/">strain kidney</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/28454041/">liver function</a> and increase risks of developing heart disease and cancer. </p>
<p><a href="https://www.hsph.harvard.edu/walter-willett/">Walter Willett</a>, chairman of the department of nutrition at the Harvard T.H. Chan School of Public Health, describes high protein intake as “<a href="https://www.nytimes.com/2016/12/06/well/eat/can-you-get-too-much-protein.html?auth=link-dismiss-google1tap">one of the fundamental processes that increase the risk of cancer</a>.” Beyond these concerns, processed supplements and protein bars are often packed with calories and may contain more sugar than a candy bar. </p>
<p>As stated in The New York Times, however, “the protein supplement market is booming among the young and healthy,” those who arguably need it least. The <a href="https://www.nytimes.com/2016/12/06/well/eat/can-you-get-too-much-protein.html#:%7E:text=Studies%20show%20that%20protein%2Drich,extra%20strain%20on%20the%20kidneys">retail sales of protein products</a> in the United States were at $9 billion in 2020, <a href="https://www.nytimes.com/2017/07/28/well/eat/how-much-protein-do-we-need.html">up from about $6.6 billion in 2015</a>. </p>
<p>Fats and carbohydrates have, along with sugar, taken turns being vilified since the identification of macronutrients (fats, proteins and carbs) over a century ago. As food writer <a href="https://www.theguardian.com/profile/bee-wilson">Bee Wilson</a> points out, protein has managed to remain the “<a href="https://www.theguardian.com/news/2019/jan/04/protein-mania-the-rich-worlds-new-diet-obsession">last macronutrient left standing</a>.” </p>
<p>Why has protein endured as the supposed holy grail of nutrients, with many of us wholeheartedly joining the quest to consume ever-greater quantities? </p>
<h2>The scoop on protein products</h2>
<p>The history of manufacturing and marketing protein-enriched products goes back almost as far as the discovery of protein itself. </p>
<p>German chemist <a href="https://www.britannica.com/biography/Justus-Freiherr-von-Liebig">Justus von Liebig</a>, one of the earliest to identify and study macronutrients, came to regard protein “<a href="http://cup.columbia.edu/book/nutritionism/9780231156561">as the only true nutrient</a>.” Liebig was also the first to mass-produce and distribute a product associated with protein in the 1860s, “Liebig’s Extract of Meat.”</p>
<p>Author Gyorgy Scrinis <a href="http://cup.columbia.edu/book/nutritionism/9780231156561">writes that through</a> “advertising and favorable publicity, the [Liebig’s Extract of Meat] company achieved ‘considerable success.’” Particularly for those who could not afford to purchase meat, the extract seemed a reasonable and satiating substitute. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A wagon being pulled by two oxen with people walking alongside." src="https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427575/original/file-20211020-20-yrpl5o.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">French advertising for Liebig’s Extract of Meat.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/7/7f/Fleischextrakt_0002781_m.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Protein consumption has remained a central component of nutritional advice and marketing campaigns ever since, even amid recycled and recurring arguments over the optimal amount of protein and whether plant or animal sources are best. </p>
<p>Around the time Liebig launched his extract company, John Harvey Kellogg, a staunch vegetarian, set out to <a href="https://www.penguinrandomhouse.com/books/216458/the-kelloggs-by-howard-markel/">redefine traditional American meals</a> at his health sanitarium in Battle Creek, Michigan.</p>
<p>The Kellogg family invented flaked breakfast cereals, granola, nut butters and various “nut meats,” which they produced, packaged, marketed and sold across the nation. Kellogg wrote countless tracts denouncing meat-heavy diets and assuring readers that high-protein plant foods could easily replace meat.</p>
<p>In an April 1910 issue of his periodical “Good Health,” Kellogg posited that “Beans, peas, lentils and nuts afford an ample proportion of the protein elements which are essential for blood making and tissue building.”</p>
<h2>How protein regained its status</h2>
<p>Alongside the meat and cereal companies consistently touting the high protein content of their foods, the first processed protein shake appeared on the market in 1952 with bodybuilder mogul Bob Hoffman’s <a href="https://physicalculturestudy.com/2016/06/15/soy-science-and-selling-bob-hoffmans-hi-proteen-powder/">Hi-Proteen Shakes, made from a combination of soy protein, whey and flavorings</a>.</p>
<p>In the 1970s through the 1990s, protein products remained visible but receded somewhat with the dietary spotlight firmly fixed on low-calorie, low-fat, sugar-free snack foods and beverages <a href="https://doi.org/10.3390/nu10010039">following the publication of studies</a> linking sugar and saturated fat consumption to heart disease. These decades gave us Slimfast and Diet Coke as well as fat-free (and guilt-free) SnackWell’s cookies and Lay’s potato chips.</p>
<p>New research in 2003, however, <a href="https://doi.org/10.1097/00075197-200311000-00005">suggested high-protein diets could aid in weight loss</a>, and protein quickly regained its former nutrient-superstar status. </p>
<p>Entire diets followed, each offering an array of protein drinks and bars. Robert Atkins first published his low-carb, high-protein “<a href="https://www.penguinrandomhouse.com/books/6004/dr-atkins-diet-revolution-by-robert-c-atkins-md/">Dr. Atkins’ Diet Revolution</a>” in 1982. It went on to become one of the 50 best-selling books of all time by the early 2000s, despite a <a href="https://doi.org/10.1056/NEJMoa022207">New England Journal of Medicine article in 2003 clearly recommending</a> that “Longer and larger studies [were] required to determine the long-term safety and efficacy of low-carbohydrate, high-protein, high-fat diets” such as Atkins’.</p>
<p>[<em>Over 115,000 readers rely on The Conversation’s newsletter to understand the world.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=100Ksignup">Sign up today</a>.]</p>
<p>The long-term pursuit of protein in hopes of achieving bigger muscles, smaller waists and fewer hunger pangs shows no sign of abating, and there has never been a dearth of those willing to take advantage of the public’s dietary goals by handing out unnecessary advice or a new protein-packed product. </p>
<p>In the end, most people living in high-income nations are consuming enough protein. When we replace meals with a protein bar or shake, we also risk missing out on the rich sources of antioxidants, vitamins and many other benefits of real food.</p><img src="https://counter.theconversation.com/content/163711/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hannah Cutting-Jones received funding from the Kluge Center at the Library of Congress as part of a 2021 American Historical Association Fellowship. </span></em></p>A food historian spent a month at the Library of Congress trying to answer the question of why we have historically been, and remain, so focused on dietary protein. Here is what she found.Hannah Cutting-Jones, Lecturer, Department of History, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1676682021-10-01T13:00:33Z2021-10-01T13:00:33ZTen small changes you can make today to prevent weight gain<figure><img src="https://images.theconversation.com/files/424187/original/file-20211001-21-c7n5u8.jpg?ixlib=rb-1.1.0&rect=17%2C0%2C3817%2C2160&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Make your daily dog walks a little longer.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/side-view-young-happy-woman-casual-1786823897">Serhii Bobyk/ Shutterstock</a></span></figcaption></figure><p>Between the <a href="https://www.acpjournals.org/doi/10.7326/0003-4819-119-7_Part_2-199310011-00004">ages of 20 and 55</a>, most adults gain between <a href="https://europepmc.org/article/NBK/nbk133218">0.5 and 1kg</a> a year, which could see some people become overweight or obese over time. This weight gain isn’t usually the result of overeating large amounts of food. Instead, it’s usually caused by eating a small amount – around <a href="https://academic.oup.com/ajcn/article/89/2/477/4596677">100-200 extra calories</a> – more than <a href="https://www.nhs.uk/common-health-questions/food-and-diet/what-should-my-daily-intake-of-calories-be/">is needed</a> each day.</p>
<p>The good news is that we may be able to prevent ourselves from gaining weight by making small changes to our diet or physical activity. <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/obr.13357">Our recent review</a> found that eating 100-200 calories less, or burning an extra 100-200 calories each day, may be enough to stop ourselves from gaining weight in the long run. This is known as a “small-changes approach”, which was first proposed in 2004 by <a href="https://academic.oup.com/ajcn/article/89/2/477/4596677">James Hill</a>, an American expert on obesity, to help people manage their weight. </p>
<p>Many small studies have investigated the use of the small-changes approach for weight management. We combined the results of these smaller studies into a larger review to get an average (and more statistically reliable) result of the effect of this approach on weight management. We looked at 19 trials – 15 of which tested a small-changes approach to prevent weight gain, and four that test this approach for weight loss. </p>
<p>We analysed the data of nearly 3,000 people in weight-gain prevention trials, and 372 people in weight-loss trials. Participants were aged between 18 and 60, 65% of whom were female. In those who used the small-changes approach to prevent weight gain, we found that participants gained almost 1kg less compared with those who didn’t use this approach over a period of eight to 14 months. The 1kg difference was statistically significant, meaning it was unlikely to be the result of chance.</p>
<p>While the small-changes approach was shown to be effective for preventing weight gain, it was not proven to be effective for weight loss. </p>
<h2>Preventing weight gain</h2>
<p>The trials we looked at used a number of different small changes to help participants prevent weight gain. Here are some of the successful techniques used in these trials:</p>
<figure class="align-center ">
<img alt="A chocolate bar cut in half." src="https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424189/original/file-20211001-27-cjhbx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">If you do decide to have something sweet, consider saving some of it for tomorrow.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/chocolate-226202980">Fabio Balbi/ Shutterstock</a></span>
</figcaption>
</figure>
<ol>
<li><p><strong>Get off the bus one stop earlier and walk the rest of the way</strong>. You may end up walking ten to 15 minutes more and this could help you burn up to <a href="https://coolconversion.com/calories-burned/Calories-burned_-walking_-10_minutes">60 calories</a>. Doing this on the way home as well could mean you burn up to 120 calories. </p></li>
<li><p><strong>Skip the chips that come as a side.</strong> Small portions of oven chips served alongside main meals contain <a href="https://www.nutracheck.co.uk/calories/calories_in_vegetables/calories_in_oven_chips_thick_cut_frozen_baked">hundreds of calories</a> . Saying no to these – or opting for a salad or vegetables as a side instead – could help you reduce your daily calorie intake by up to 200 calories. </p></li>
<li><p><strong>Switch from a regular to a diet drink</strong>. Although it might not taste the same, making this switch could reduce your calorie intake by <a href="https://www.healthyman.com.au/how-many-calories-in-can-of-coke/">145 calories</a>. However, recent research suggests that <a href="https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2784545?utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_term=092821">switching to diet drinks</a> may not be great for weight management – so choosing to drink water instead of your regular fizzy drink might be best. </p></li>
<li><p><strong>Have an Americano instead of a latte.</strong> The milk in a regular latte can contain up to <a href="https://www.fatsecret.com/calories-nutrition/generic/milk-cows-fluid-whole?portionid=1136439&portionamount=300.000#:%7E:text=There%20are%20186%20calories%20in%20300%20ml%20of,beginning%20any%20weight%20loss%20effort%20or%20diet%20regimen..">186 calories</a>, so switching to an Americano could prevent weight gain.</p></li>
<li><p><strong>Add one less tablespoon of oil while cooking.</strong> One tablespoon of olive oil, for example, contains slightly over <a href="https://www.fatsecret.com/calories-nutrition/usda/olive-oil?portionid=30460&portionamount=1.000#:%7E:text=There%20are%20119%20calories%20in%201%20tablespoon%20of,Common%20Serving%20Sizes%3A%20Star%20Extra%20Light%20Olive%20Oil">100 calories</a>, so using less can be one way of avoiding additional calories. </p></li>
<li><p><strong>If you have something sweet, save half of it for tomorrow.</strong> Eating only half a KitKat, for example, could reduce your calorie intake by about 102 calories – and give you something to look forward to tomorrow. </p></li>
<li><p><strong>Take one or two fewer potatoes in your roast dinner</strong>. One medium roast potato can contain as many as <a href="https://www.fatsecret.com/calories-nutrition/generic/white-potato-roasted?portionid=21189&portionamount=1.000">200 calories</a>, so be mindful of how many you put on your plate. </p></li>
<li><p><strong>Take phone meetings while walking.</strong> You could burn an extra <a href="https://fatcalories.org/interesting-about-calories/30-minute-walk-how-many-calories.html">100 calories</a> if you opted to take a 30-minute phone call on the go. </p></li>
<li><p><strong>Avoid sweets.</strong> Saying no to cakes, biscuits and other sweets could help you easily cut an extra 100-200 calories from your diet – maybe more, depending on the food.</p></li>
<li><p><strong>Take your dog for an extra 30-minute brisk walk each day.</strong> The dog will appreciate it, and you could burn over <a href="https://burned-calories.com/sport/walking-fast#:%7E:text=Then%20we%20multiply%20this%20with%200.0175%20and%20the,minutes%20of%20Walking%20%28fast%29%20you%20burn%20154%20kcal.">150 calories</a>. </p></li>
</ol>
<p>The small-changes approach has many advantages for managing weight. First, small changes are easier to incorporate into everyday life over larger ones. For example, it’s easier to eat 100-200 fewer calories a day than to eat 500 fewer calories each day (basically, an entire meal). Small changes are also easier to <a href="https://pubmed.ncbi.nlm.nih.gov/33651994/">maintain in the long run</a>, which is key to managing weight. And, if people succeed at making these small changes, it may lead them to make <a href="http://happyheartfamilies.citymax.com/f/self_efficacy.pdf">bigger changes</a> in their life.</p><img src="https://counter.theconversation.com/content/167668/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Making small changes daily can help prevent weight gain in the long run.Claire Madigan, Senior Research Associate, Centre for Lifestyle Medicine and Behaviour, Loughborough UniversityHenrietta Graham, PhD Researcher, Sport, Exercise and Health Sciences, Loughborough UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1661342021-08-19T15:50:11Z2021-08-19T15:50:11ZMetabolism may not slow after 20 – so why do we still gain weight?<figure><img src="https://images.theconversation.com/files/416966/original/file-20210819-15-qlp2nw.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4500%2C2991&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Don't blame your metabolism for middle age weight gain.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/male-on-weight-scale-check-diet-1087799819">Monthira/ Shutterstock</a></span></figcaption></figure><p>For a long time, it was believed that after the age of 20 your metabolism decreased dramatically – making it harder to lose weight and keep in shape. But a <a href="https://pubmed.ncbi.nlm.nih.gov/34385400/">recent study</a> has shown our metabolism – also known as energy expenditure – stays relatively stable between the ages of 20 and 60, before decreasing at older ages. </p>
<p>The researchers looked at existing studies on energy expenditure from 29 different countries. In total, they looked at data on around 6,400 people from birth to 95 years of age. Each study measured energy expenditure using a method called <a href="https://doubly-labelled-water-database.iaea.org/dataOverview">doubly labelled water</a>. This has participants drink a special type of water, in which a safe, non-radioactive marker has been added. The marker identifies the hydrogen and oxygen present in the water, which allows researchers to track how quickly the body processes both. Urine samples are then taken from each person to track the rate they’ve both travelled through the body. This gives researchers an accurate measure of a person’s <a href="https://www.bbc.co.uk/bitesize/guides/zg2xxnb/revision/1">metabolic rate</a> – the amount of energy they used in a day.</p>
<p>The analysis showed that energy expenditure (metabolism) rapidly increased from birth to one year. After this, energy expenditure gradually decreased until the age of 20, at which point it became stable until age 60 – even during pregnancy. After 60 was when energy expenditure begins to fall. These findings were true even when researchers took into account different factors – such as physical activity and body composition (how much fat or muscle a person had and how much they weighed) – which can affect a person’s metabolism. </p>
<p>This study builds on our understanding of the human metabolism. Knowing how our metabolism may (or may not) change during our lives can be important for knowing how diseases – such as obesity, diabetes, heart disease and even some cancers – can be treated. </p>
<p>But one problem with the study’s findings is that they didn’t take into account a person’s energy intake. Many people still see their weight increase as they get older, despite their metabolism staying relatively the same throughout their life. This suggests that weight gain isn’t a result of a slowing metabolism. Rather, it’s more likely to be due to eating more food (energy) than our body uses. </p>
<h2>Energy and weight gain</h2>
<p>Metabolism is affected by many factors – including the <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/339317/SACN_Dietary_Reference_Values_for_Energy.pdf">amount of food we eat</a>, how much physical activity we get, weight, and whether we have a lot of muscle. Metabolism can also affect how energy is obtained from foods. For example, when we <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897177/">eat more than we need</a>, the body is more likely to use carbohydrates and protein from these foods as fuel, and store the fat – causing weight gain. Weight gain and obesity are both linked to metabolic rate, caused by eating more energy than we use.</p>
<figure class="align-center ">
<img alt="A family sitting around a dinner table eating." src="https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=541&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=541&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417001/original/file-20210819-15-1e93mpt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=541&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s important to be aware of what – and how much – you’re eating.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/big-multigenerational-family-dinner-process-top-1679988679">Soloviova Liudmyla/ Shutterstock</a></span>
</figcaption>
</figure>
<p>With so many things to keep track of, it can be difficult to understand how best to manage one’s weight. This is why experts have created <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/339317/SACN_Dietary_Reference_Values_for_Energy.pdf">national recommendations</a> of how many calories people of different ages and activity levels should get. These recommendations are made using data on energy expenditure – rather than energy intake. This is because measuring expenditure is thought to be more accurate than measuring energy intake, which is usually done by asking people to self-report what they eat daily. </p>
<p>But the problem with using data on energy expenditure is that these recommendations are made using an average value – so what works for some may not work for everyone. For example, some people who are not very active may need to eat less than guidelines recommend. This may also be why we’re seeing such a mismatch with energy expenditure levels and reported energy intakes in British adults. In fact, <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/485982/familyfood-2014report-17dec15.pdf">some studies</a> suggest they are eating well below what the daily recommendations are – and yet we’re still seeing more people <a href="https://www.nuffieldtrust.org.uk/resource/obesity">becoming overweight and obese</a> in the UK every year. </p>
<p>Why people appear to be eating below the national recommendations could be due to a number of reasons. For example, research on energy intake shows that some participants may <a href="http://www.behaviouralinsights.co.uk/wp-content/uploads/2016/08/16-07-12-Counting-Calories-Final.pdf">misreport</a> how much they eat daily in surveys. Under-reporting may not be the whole story. Even apps which <a href="https://pubmed.ncbi.nlm.nih.gov/30089491/">measure food intake</a> in detail also give lower values of the amount people eat compared to recommendations. This can make it look like people are actually eating less than they need. Other things, such as amount of activity and body size can affect how much energy we need. Recommendations may not take these things adequately into account.</p>
<p>What is promising about the data from this study is that it used a more accurate measure of energy expenditure with people of all ages than some studies have used in the past. This study shows us that energy needs don’t appear to change dramatically over an adult’s life, so these findings may well be useful for adjusting our current recommendations for energy requirements. But it will be key to match new recommendations on energy intakes to how requirements can vary from each person according to their activity levels and body weight. It will also be important to develop better ways of personalising recommendations, so that each person can manage their weight most effectively. </p>
<p>But there are still many simple ways a person can prevent weight gain throughout their life. Keeping physically active and having a healthy diet are both important. Although there can be some margin of error, recording food intake daily can help track how much you’re eating, and can be useful for knowing where you may need to cut back if your weight increases.</p><img src="https://counter.theconversation.com/content/166134/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Janet Cade Chairs the Board of Dietary Assessment Ltd and developed myfood24. She has received funding from the UK Medical Research Council in the past. She is Hon Sec for the Association for Nutrition. </span></em></p>Eating more than your metabolism burns is likely to cause you to gain weight.Janet Cade, Professor of Nutritional Epidemiology and Public Health, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1630432021-06-24T18:17:19Z2021-06-24T18:17:19ZTour de France: How many calories will the winner burn?<figure><img src="https://images.theconversation.com/files/407957/original/file-20210623-17-1ye6i7d.jpg?ixlib=rb-1.1.0&rect=0%2C16%2C1569%2C1015&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tour de France riders have to eat constantly to replenish the energy they burn. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/filipbossuyt/50369397086/">Filip Bossuyt/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=255&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=255&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=255&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=321&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=321&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407956/original/file-20210623-21-1kl10a5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=321&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">CC-BY-ND.</span>
</figcaption>
</figure>
<p>Imagine you begin pedaling from the <a href="https://www.letour.fr/en/stage-17">start of Stage 17</a> of <a href="https://www.letour.fr/en">this year’s Tour de France</a>. First, you would bike approximately 70 miles (112 km) with a gradual increase in elevation of around 1,300 feet (400 m). But you’ve yet to hit the fun part: the <a href="https://en.wikipedia.org/wiki/Hautes-Pyr%C3%A9n%C3%A9es">Hautes-Pyrénées</a> mountains. Over the next 40 miles (64 km) you would have to climb three <a href="https://www.letour.fr/en/stage-17">mountain peaks with a net increase of a mile (1.6 km) in elevation</a>. On the fittest day of my life, I might not even be able to finish Stage 17 – much less do it in anything remotely close to the five hours or so the winner will take to finish the ride. And Stage 17 is just one of 21 stages that must be completed in the 23 days of the tour.</p>
<p><a href="https://scholar.google.com/citations?user=eHzYy_EAAAAJ&hl=en&oi=ao">I am a sports physicist</a>, and I’ve <a href="http://johnericgoff.blogspot.com/">modeled the Tour de France</a> for nearly two decades using terrain data – like what I described for Stage 17 – and the laws of physics. But I still cannot fathom the physical capabilities needed to complete the world’s most famous bike race. Only an elite few humans are capable of completing a Tour de France stage in a time that’s measured in hours instead of days. The reason they’re able to do what the rest of us can only dream of is that these athletes can produce enormous amounts of power. Power is the rate at which cyclists burn energy and the energy they burn comes from the food they eat. And over the course of the Tour de France, the winning cyclist will burn the equivalent of roughly 210 Big Macs.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/S4O5voOCqAQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Cycling is a game of watts</h2>
<p>To make a bicycle move, a Tour de France rider transfers energy from his muscles, through the bicycle and to the wheels that push back on the ground. The faster a rider can put out energy, the greater the power. This rate of energy transfer is often measured in watts. Tour de France cyclists are capable of generating enormous amounts of power for incredibly long periods of time compared to most people.</p>
<p>For about 20 minutes, a fit recreational cyclist can consistently put out <a href="https://www.roadbikerider.com/average-wattage-cycling/">250 watts to 300 watts</a>. Tour de France cyclists can produce <a href="https://www.bicycling.com/racing/a20041587/cool-things-we-learned-from-tour-de-france-strava-files/">over 400 watts for the same time period</a>. These pros are even capable of <a href="https://www.cyclist.co.uk/in-depth/539/how-much-better-are-pro-cyclists">hitting 1,000 watts</a> for short bursts of time on a steep uphill – <a href="https://www.dailymotion.com/video/x6l981y">roughly enough power</a> to run a <a href="https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)">microwave oven</a>.</p>
<p>But not all of the energy a Tour de France cyclist puts into his bike gets turned into forward motion. Cyclists battle air resistance and frictional losses between their wheels and the road. They get help from gravity on downhills but they have to fight gravity while climbing. </p>
<p>I incorporate all of the physics associated with cyclist power output as well as the effects of gravity, air resistance and friction <a href="http://johnericgoff.blogspot.com/">into my model</a>. Using all that, I estimate that a typical Tour de France winner needs to put out an average of about 325 watts over the roughly 80 hours of the race. Recall that most recreational cyclists would be happy if they could produce 300 watts for just 20 minutes!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A pile of hamburgers." src="https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407960/original/file-20210623-21-fn773v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Racers in the Tour de France need to eat three to four times as many calories as a person does normally.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-stack-against-black-background-royalty-free-image/1208752640?adppopup=true">Pietro Agliata/EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<h2>Turning food into miles</h2>
<p>So where do these cyclists get all this energy from? Food, of course! </p>
<p>But your muscles, like any machine, can’t convert 100% of food energy directly into energy output – muscles can be anywhere between <a href="https://www.pearson.ch/HigherEducation/Pearson/EAN/9780139228162/Mechanics-Heat-and-the-Human-Body">2% efficient when used for activities like swimming and 40% efficient in the heart</a>. In my model, I use an average efficiency of 20%. Knowing this efficiency as well as the energy output needed to win the Tour de France, I can then estimate how much food the winning cyclist needs.</p>
<p>Top Tour de France cyclists who complete all 21 stages burn about 120,000 calories during the race – or an average of nearly 6,000 calories per stage. On some of the more difficult mountain stages – like this year’s Stage 17 – racers will burn close to 8,000 calories. To make up for these huge energy losses, riders eat delectable treats such as <a href="https://www.cyclingweekly.com/news/racing/tour-de-france/this-is-what-you-have-to-eat-to-compete-in-the-tour-de-france-182775">jam rolls, energy bars and mouthwatering “jels” so they don’t waste energy chewing</a>. </p>
<p><a href="https://www.procyclingstats.com/rider/tadej-pogacar">Last year’s winner</a>, Tadej Pogačar, weighs only 146 pounds. Tour de France cyclists don’t have much fat to burn for energy. They have to keep putting food energy into their bodies so they can put out energy at what seems like a superhuman rate. So this year, while watching a stage of the Tour de France, note how many times the cyclists eat – now you know the reason for all that snacking.</p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/163043/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Eric Goff does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Riders in the 2021 Tour de France will ride more than 2,100 miles (3,400 km) over the 21 flat and mountainous stages of the race. And they will burn an incredible amount of energy while doing so.John Eric Goff, Professor of Physics, University of LynchburgLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1546202021-02-16T13:38:41Z2021-02-16T13:38:41ZDieting may slow metabolism – but it doesn’t ruin it<figure><img src="https://images.theconversation.com/files/384472/original/file-20210216-19-l7hmwo.jpg?ixlib=rb-1.1.0&rect=289%2C213%2C4034%2C3022&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The body slows your metabolism on purpose to prevent weight loss. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/diet-nutrition-113341153">Gts/ Shutterstock</a></span></figcaption></figure><p>When it comes to dieting, research shows the majority of people will regain some – if not most – of the <a href="https://academic.oup.com/ajcn/article/74/5/579/4737391">weight they’ve lost</a>. While there are many reasons why this weight regain may happen, some popular claims online are that it’s because dieting permanently wrecks your metabolism. But while it’s true that dieting slows your metabolism, it also improves your metabolism in many positive ways.</p>
<p>When we talk about metabolism, we’re typically referring to your <a href="https://formnutrition.com/inform/everything-you-need-to-know-about-your-basal-metabolic-rate/">metabolic rate</a>. This is the number of calories your body burns at rest. Of course, the more activity we do, the more calories we burn. In order to lose weight through dieting, you need to consume fewer calories than you’re using. This forces the body to use its energy stores – like fat – to meet the shortfall. Your metabolic rate will also change as a result.</p>
<p>The loss of lean tissue (muscle) when you diet – which burns around <a href="https://www.nature.com/articles/0803537">15-25 calories</a> per kilogram each day – <a href="https://academic.oup.com/ajcn/article/112/5/1157/5906569">lowers resting metabolic rate</a>, meaning you need fewer calories than you previously did. But the body also deliberately <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/">slows down metabolism</a> to preserve energy stores and minimise weight loss. </p>
<p>When the body senses <a href="https://www.nature.com/articles/0803516">depleted fat stores</a> it triggers adaptive thermogenesis, a process which further reduces resting metabolic rate – and may stunt weight loss <a href="https://pubmed.ncbi.nlm.nih.gov/26627218/">despite strict dieting</a>. Adaptive thermogenesis can kick in <a href="https://academic.oup.com/ajcn/article/102/4/807/4564599">within three days</a> of starting a diet, and is suggested to persist way beyond dieting – even hampering weight maintenance and <a href="https://academic.oup.com/ajcn/article/88/4/906/4650207">favouring weight regain</a>.</p>
<p>One example of adaptive thermogenesis’s effect was seen in a widely publicised <a href="https://pubmed.ncbi.nlm.nih.gov/27136388/">2016 study</a> which looked at former contestants of US reality TV show “The Biggest Loser”. It showed that participants had a significant decrease in their metabolic rate, even several years after initial weight loss. Participants needed to eat up to <a href="https://pubmed.ncbi.nlm.nih.gov/27581740/">500 calories less</a> than expected daily. </p>
<p>Other studies have also shown metabolic slowing with weight loss, but with much smaller decreases (<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5097076/">around 100 calories fewer a day</a> to maintain weight). However, there’s less certainty whether this slowing persists once people are <a href="https://pubmed.ncbi.nlm.nih.gov/32844188/">weight stable</a>. </p>
<figure class="align-center ">
<img alt="A man fills out a diet plan." src="https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/384473/original/file-20210216-17-856873.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Adaptive thermogenesis may stunt weight loss – even if you follow a strict diet.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/healthy-lifestyle-diet-nutrition-concept-520169236">Rawpixel.com</a></span>
</figcaption>
</figure>
<p>Research seems to show that most adaptive thermogenesis happens in the actual <a href="https://pubmed.ncbi.nlm.nih.gov/32599082/">dieting phase</a> as a temporary response to the amount of weight being lost. Overall, we don’t have <a href="https://academic.oup.com/ajcn/article/108/4/658/5129189">conclusive evidence</a> to support the notion that metabolic rate remains slowed over the long term (over a year post-diet). </p>
<p>It’s worth noting many factors can affect metabolic rate, so changes to it after dieting may vary between people. For example, one study on fasting diets showed metabolic rate indeed decreases as a result – but those who had the <a href="https://pubmed.ncbi.nlm.nih.gov/32118268/">the greatest decrease</a> in metabolic rate already had a higher metabolic rate to begin with. <a href="https://pubmed.ncbi.nlm.nih.gov/28163316/">Overestimaing metabolic rates</a> at the start of a study or <a href="https://pubmed.ncbi.nlm.nih.gov/20164308/">errors in predicting</a> metabolic rate after weight loss could both also affect study results. </p>
<p>It’s agreed that metabolic rate slows because of weight loss, due to both decreasing body size, and as a way of preserving key tissues and fuel reserves. But there’s currently no consensus on how much it slows by. Quantifying and predicting this slowing is something we’re currently researching <a href="https://www.cambridge.org/core/services/aop-cambridge-core/content/view/96FF7F85D9D8BE5BA32C69BEAB754BF4/S0029665119001253a.pdf/div-class-title-predicting-weight-loss-using-differential-equations-prelude-div.pdf">at the University of Surrey</a>.</p>
<h2>Metabolic changes</h2>
<p>A decrease in metabolic rate is just one change that occurs with weight loss, however. </p>
<p>When we lose weight, the main change we see is a decrease in body fat. This decrease is actually our fat cells shrinking in size – they don’t actually disappear. This <a href="https://pubmed.ncbi.nlm.nih.gov/25614203/">shrinking of fat cells</a> signals the body’s fuel stores are emptying, causing a drop in the hormone <a href="https://joe.bioscientifica.com/view/journals/joe/223/1/T83.xml">leptin</a>. Ordinarily leptin inhibits appetite and increases metabolic rate – but when leptin levels plumment, metabolic rate slow and hunger increases.</p>
<p>The gut also releases fewer <a href="https://pubmed.ncbi.nlm.nih.gov/29364588/">incretins</a> (hormones which regulate appetite) when we lose weight, which could <a href="https://pubmed.ncbi.nlm.nih.gov/22029981/">persist beyond dieting</a>. Less leptin and fewer incretins may make us feel hungrier and can lead to <a href="https://pubmed.ncbi.nlm.nih.gov/29717270/">over eating</a>.</p>
<p>When fat cells shrink, they’re able to take up glucose and store fat more efficiently to help restore lost fuel. Your body also <a href="https://diabetes.diabetesjournals.org/content/62/6/1990.long">creates more fat cells</a> so that you can store more fat in the future to better cope with this calorie “crisis” the next time it happens.</p>
<p>But as contradictory as it sounds, all these changes actually result in a more efficient and <a href="https://pubmed.ncbi.nlm.nih.gov/31303390/">ultimately healthier metabolism</a>. For example, smaller fat cells are better for our health, as <a href="https://www.sciencedirect.com/science/article/pii/S000293430801019X?via%3Dihub">over-inflated “sick” fat cells</a> don’t work as well in getting rid of surplus sugar and fat. This can lead to high levels of sugar and fat in the blood, increasing risk of insulin resistance, diabetes, and cardiovascular disease.</p>
<p>So dieting doesn’t technically ruin your metabolism but rather improves it by helping it work better. But without care, this <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5513193/">metabolic improvement</a> can conspire against you to <a href="https://pubmed.ncbi.nlm.nih.gov/32099104/">regain the weight, and even overshoot</a> your original weight. </p>
<p>Studies show exercise (or simply physical activity) may be one way to prevent weight regain, by improving our ability to <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-789X.2008.00547.x">maintain our weight</a> and can potentially <a href="https://pubmed.ncbi.nlm.nih.gov/18356845/">minimise metabolic slowing</a>. Exercise can also help <a href="https://cdnsciencepub.com/doi/10.1139/apnm-2017-0280">regulate appetite and fuel burning</a> in the short term, and may make weight loss more <a href="https://pubmed.ncbi.nlm.nih.gov/28543022/">sustainable</a> in the long term.</p><img src="https://counter.theconversation.com/content/154620/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Certain body processes aim to prevent weight loss by slowing our metabolic rate.Adam Collins, Principal Teaching Fellow, Nutrition, University of SurreyAoife Egan, PhD Researcher, Mathematical Modelling of Weight-loss, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1492312020-12-28T13:35:57Z2020-12-28T13:35:57ZWhether slow or fast, here’s how your metabolism influences how many calories you burn each day<figure><img src="https://images.theconversation.com/files/376587/original/file-20201223-15-3whpcv.jpg?ixlib=rb-1.1.0&rect=194%2C72%2C5197%2C3338&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Why does it seem like some people can eat anything and not gain a pound while others are the opposite?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/mother-looking-at-son-royalty-free-image/535080170">Heide Benser/The Image Bank via Getty Images</a></span></figcaption></figure><p>It’s a common dieter’s lament: “Ugh, my metabolism is so slow, I’m never going to lose any weight.” </p>
<p>When people talk about a fast or slow metabolism, what they’re really getting at is how many calories their body burns as they go about their day. The idea is that someone with a slow metabolism just won’t use up the same amount of energy to do the same task as does someone with a fast metabolism.</p>
<p>But does the speed of metabolism really vary all that much from person to person? I’m a nutrition scholar who focuses on the biological, environmental and socioeconomic factors that influence body composition. This question is trickier than it might first seem – and whatever the current speed of your metabolism, there are things that will nudge it into lower or higher gears.</p>
<h2>Your body’s energy needs</h2>
<p>Metabolism is a biological term that refers to all the chemical reactions needed to maintain life in an organism. Your metabolism accomplishes three main jobs: <a href="https://www.ncbi.nlm.nih.gov/books/NBK26882/">converting food into energy</a>; breaking down food into its building blocks for protein, lipid, nucleic acid and some carbohydrate; and eliminating nitrogen wastes. </p>
<p>If you’re agonizing over the speed of your metabolism, you’re probably focused on how much energy you’re getting from the foods you eat and how much your body is using. The <a href="https://www.ncbi.nlm.nih.gov/books/NBK218769/">energy value of a food</a> is measured in calories.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="older couple eat energy bars on a bike ride" src="https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/376476/original/file-20201222-23-q2kzbq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Metabolism can be a way to think about the energy you take in and the energy you expend.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/african-american-couple-with-bikes-eating-snack-royalty-free-image/521419354">kali9/E+ via Getty Images</a></span>
</figcaption>
</figure>
<p>Your caloric needs can be divided into two categories. </p>
<p>Basal metabolic rate is the minimum amount of <a href="https://doi.org/10.1079/phn2005801">calories required for basic functions at rest</a>. Resting energy expenditure is the amount of calories you body use while resting or sleeping – <a href="https://doi.org/10.4103/ijem.IJEM_484_16">about 60%-65% of your total energy expenditure</a>. It doesn’t take into account the calories you’d need to power everything else you do – moving around, or activity energy expenditure (25%-30%), thinking, even digesting food (5%-10%). So your total energy expenditure combines the two: your resting energy expenditure plus your energy expenditures for other activities.</p>
<h2>Coming up with a number</h2>
<p>The <a href="https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines/appendix-2/">estimated daily caloric intake needs</a> for an adult woman of 126 pounds (57 kilograms) range from 1,600 to 2,400 calories per day. For a man of 154 pounds (70 kilograms), daily calorie needs can range from about 2,000 to 3,000 calories per day. That’s about 11-14 calories per pound of body weight (25-30 calories per kilogram).</p>
<p>In contrast, <a href="https://www.ncbi.nlm.nih.gov/books/NBK560758/">infants burn about 50 calories per pound of weight per day</a> (120 calories per kilogram). This requirement continuously decreases as the child ages. So infants have the highest metabolism of all. This extra calorie requirement is necessary <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2642618/">for growth</a>.</p>
<p>So if two women of the same weight can have caloric needs that vary by as much as 30%, does that mean the woman whose body uses up more calories has a faster metabolism than the woman whose body uses fewer calories? Not necessarily. One woman might spend more of her day physically active and thus need more energy to power her walking commute and after-work kickboxing class, for instance. </p>
<p>Beyond those rough guideline ranges, there are many ways to estimate resting and total energy expenditure if you want to figure out your body’s specific calorie needs. One common and easy method is to use predictive formulas <a href="https://doi.org/10.1093/ajcn/51.2.241">such as the Mifflin-St. Jeor</a> or <a href="https://pubmed.ncbi.nlm.nih.gov/11817239/">Harris-Benedict</a> equations which are <a href="https://doi.org/10.1016/j.nutres.2007.01.016">based on your age, height, weight and gender</a> to figure out how much energy your body needs just to be alive. To calculate total energy expenditure, you also need to add the activity factor. </p>
<p><a href="https://www.indirectcalorimetry.net/2017/10/04/understanding-indirect-calorimetry/">Indirect calorimetry</a> is another way to estimate metabolic rate. Energy expenditure is calculated by measuring the amount of oxygen used, and carbon dioxide released by the body. Your body relies on oxygen to perform all its jobs of metabolism. For every liter of oxygen you use, you <a href="https://icuprimaryprep.files.wordpress.com/2012/05/nutrition-and-metabolism.pdf">use about 4.82 calories of energy</a> from glycogen or fat. Respiratory indirect calorimetry is typically done at a doctor’s office, though small, portable, more affordable devices are increasingly being brought to market. </p>
<h2>Factors that influence metabolic rate</h2>
<p>Metabolic rate and calorie requirements vary from person to person <a href="https://www.ncbi.nlm.nih.gov/books/NBK221834/">depending on factors</a> such as genetics, gender, age, body composition and amount of exercise you do. </p>
<p>Health status and certain medical conditions may also influence metabolism. For example, one regulator of metabolism is the thyroid gland, located at the front of the neck just below the Adam’s apple. <a href="https://doi.org/10.1152/physrev.00030.2013">The more thyroxin a person’s thyroid gland produces</a>, the higher that person’s basal metabolic rate will be.</p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p>
<p>Having a fever can also affect a person’s basal metabolic rate. For <a href="https://www.ncbi.nlm.nih.gov/books/NBK331/">each increase of 0.9 degrees Fahrenheit (0.5 C)</a> in a person’s internal body temperature, their basal metabolic rate increases by approximately 7%.</p>
<p>Other medical conditions that influence basal metabolic rate can include muscle wasting (atrophy), <a href="https://derangedphysiology.com/main/required-reading/endocrinology-metabolism-and-nutrition/Chapter%20318/physiological-adaptation-prolonged-starvation">prolonged starvation</a>, low oxygen levels in the body (hypoxia), muscular disorders, depression and <a href="https://doi.org/10.2337/diabetes.48.8.1607">diabetes</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman with grey hair working out with small weights" src="https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/376477/original/file-20201222-50514-1lwoh30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It takes more energy to maintain muscle than fat in your body.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/mature-mexican-woman-working-out-royalty-free-image/1168227653">adamkaz/E+ via Getty Images</a></span>
</figcaption>
</figure>
<p>Another important factor is body composition. For example, an overweight woman with a body composition of 40% body fat and 75 pounds of muscle mass will burn fewer calories while resting than a woman with 30% body fat and 110 pounds of muscle mass; <a href="https://doi.org/10.1038/oby.2011.256">muscle tissue is more metabolically active than fat tissue</a> in the body. </p>
<p>This is also why <a href="https://doi.org/10.1016/j.arr.2009.08.002">basal metabolic rate decreases with age</a>. As people get older, they typically lose muscle mass and gain fat tissue – which equates to a <a href="https://doi.org/10.3143/geriatrics.30.572">decrease in basal metabolic rate of approximately 1% to 2% per decade</a>.</p>
<p>If you really want to give your metabolism a jolt, the easiest way is to bump up your muscle mass and activity level. By increasing muscle mass, you’ll also increase the base number of calories needed <a href="https://doi.org/10.1172/JCI114857">to maintain those muscles</a>. Instead of complaining about a slow metabolism, you can try to turn it up to be at least a bit quicker.</p>
<p><em>This article was updated to include metric measurements for weights.</em></p><img src="https://counter.theconversation.com/content/149231/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Terezie Tolar-Peterson does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There are some factors you can’t change about your metabolism. But there are things you can do to influence how much energy your body uses over the course of the day.Terezie Tolar-Peterson, Associate Professor of Food Science, Nutrition & Health Promotion, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1506912020-12-10T13:35:49Z2020-12-10T13:35:49ZWhy we’re so bad at counting the calories we eat, drink or burn<figure><img src="https://images.theconversation.com/files/374019/original/file-20201209-22-1ln4wx3.jpg?ixlib=rb-1.1.0&rect=48%2C116%2C1839%2C945&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Getting the portions right can be tricky. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/typical-swedish-scandinavian-christmas-food-royalty-free-image/1183586464">knape/E+ via Getty Images</a></span></figcaption></figure><p>People <a href="https://www.seattletimes.com/seattle-news/health/you-do-eat-more-at-the-holidays-evolution-trained-you-to/">often eat more than usual</a> around the holidays – and this year more than most as the <a href="https://www.nytimes.com/2020/12/04/health/many-of-us-are-stress-eating-because-of-the-pandemic.html">pandemic prompts many to stress eat</a>.</p>
<p>A common way to avoid putting on extra weight is by choosing healthier options with fewer calories per serving. One problem with this strategy is that <a href="https://www.sharecare.com/health/portion-control/how-large-portions-affect-weight">people tend to eat more of something</a> if they think it’s healthier. For example, a guest at a holiday feast may fill her plate with Brussels sprouts instead of carb-heavy foods, like mashed potatoes, that people associate with more weight gain. </p>
<p>But that works only if you’re reasonably good at counting or comparing calories across dishes and quantities – a topic we explored in a <a href="https://cdn.theconversation.com/static_files/files/1356/woolleyliujcr.pdf?1607191495">series of studies</a> that will be published in the Journal of Consumer Research. We learned it’s a lot harder to do than you might think. </p>
<h2>Counting calories</h2>
<p>Health experts generally recommend two ways of evaluating the caloric content of foods: <a href="http://www.doi.org/10.1111/obr.12165">try to come up with exact numerical counts</a> in food portions or simply think in qualitative terms about high- and low-calorie foods – brie cheese and mashed potatoes = high, peas and Brussels sprouts = low. </p>
<p><a href="https://www.economist.com/1843/2019/02/28/death-of-the-calorie">Those who favor the latter method</a> contend it will lead to similar conclusions but will be easier for most people to do regularly. But our research suggests these two methods result in very different calorie estimates – with a significant impact on dieting. </p>
<p>In our first study, we recruited several hundred undergraduate students and showed them two pictures: an image of a plate of 20 grams of chocolate-covered almonds and one with 33 grams of plain roasted almonds – without disclosing the actual weights.</p>
<p>We then randomly asked half of them to guess how many calories each plate had on a scale from “very few” to “a lot” and the others to provide their best precise numerical estimate. Participants were then shown the images again and asked to pick the lower-calorie option of the two – which we then let them eat. </p>
<figure class="align-center ">
<img alt="A plate of almonds next to a plate of a smaller quantity of chocolate-covered almonds" src="https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373959/original/file-20201209-23-1gn56ld.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Which plate has more calories?</span>
<span class="attribution"><span class="source">Kaitlin Woolley</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>We found that participants who used the scale thought the larger portion of almonds had fewer calories than the chocolate-covered ones. And when choosing a low-calorie snack, most students chose the regular almonds. On the other hand, most of the students who made numerical guesses correctly chose the chocolate-covered almonds as the less caloric option. On average, they estimated the chocolate-covered almonds had about 111 calories, versus 117 for the regular ones. </p>
<p>But even this group greatly underestimated just how many calories the larger portion of regular almonds had: 200, double the number of calories in the chocolate-covered ones. </p>
<p>We believe the reason those who rated their estimates on a scale got it so wrong is because they were thinking qualitatively rather than quantitatively. A scale from “very few” to “a lot” sounds similar to “very healthy” to “very unhealthy.” Participants got so focused on the notion that the roasted almonds are healthier that they forget that the amount they consume is also an important factor in estimating calories. The mental effort of trying to come up with an actual figure forces one to consider both health and quantity.</p>
<h2>Turkeys and burgers</h2>
<p>We then repeated variations of the first study, including one in which we had participants estimate the number of calories burned in various low- and high-intensity workouts, with similar results. We also considered different foods.</p>
<p>For that study, we asked 277 people who had eaten at Subway and McDonald’s in the previous year to estimate calories in a 12-inch turkey sub sandwich and a cheeseburger. People asked to make scaled, qualitative estimates for both thought the turkey sub had fewer calories, while those who made numeric estimates correctly guessed that the sub actually had more calories – in fact, 510 versus just 300 for the burger.</p>
<p>To see if we can find a way to correct for this consistent error involving qualitative estimates, we set up the earlier almond study but first asked some participants to look at 12 pictures of different-sized snack plates and judge the portion size on a sliding scale from very small to very large.</p>
<p>Participants then estimated calorie amounts for the small plate of chocolate-covered almonds and the large plate of regular almonds. Drawing their attention to portion size helped all participants become more accurate in their estimates, which was especially useful for people making qualitative estimates.</p>
<p>[<em>Insight, in your inbox each day.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=insight">You can get it with The Conversation’s email newsletter</a>.]</p>
<p>So, while people are not all that good at counting calories, whether consumed in food or burned from exercise, there are ways to get better at it. Just bear this in mind at the next feast, when you’re tempted to cover your plate with Brussels sprouts.</p><img src="https://counter.theconversation.com/content/150691/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>People worried about gaining weight over the holidays may try to estimate how many calories are in the foods they put on their plates. But it’s not as easy as it looks.Kaitlin Woolley, Assistant Professor of Marketing, Cornell UniversityPeggy Liu, Assistant Professor of Business Administration and Ben L. Fryrear Faculty Fellow, University of PittsburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1503412020-12-08T12:09:03Z2020-12-08T12:09:03ZMetabolic confusion diet won’t boost metabolism – but it could have other benefits<figure><img src="https://images.theconversation.com/files/373577/original/file-20201208-17-5yf5ho.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C7488%2C4985&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The diet could reinforce bad eating habits.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/concept-mock-fresh-salad-fried-chicken-496719403">Bon Appetit/ Shutterstock</a></span></figcaption></figure><p>The “metabolic confusion” diet is one of the latest fad diets to be blowing up on social media. Like many fad diets, it promises you can lose weight while still eating what you want. </p>
<p>Fans of the diet claim that by switching between very low calorie days and high calorie days, you can lose weight while simultaneously speeding up your metabolism. It may sound promising, but there’s no research to back these claims.</p>
<p>The metabolic confusion diet is similar to <a href="https://formnutrition.com/inform/intermittent-fasting/">intermittent fasting</a>, but without the extremes of energy (calorie) restriction. A person on the diet might, for example, eat only 1,200 calories one day, then eat 2,000 calories the next. Although there hasn’t been any research looking specifically at the metabolic confusion diet, we might compare it with a popular form of intermittent fasting: the <a href="https://theconversation.com/heres-the-skinny-on-fasting-for-weight-loss-the-5-2-diet-13820">5:2 diet</a> where you eat as usual for five days, then either fast for two days or only eat around 500 calories. </p>
<p>Despite being able to eat as much as you like on “feed days”, people <a href="https://pubmed.ncbi.nlm.nih.gov/32873926/">may not feel more hungry</a> and still end up eating <a href="https://pubmed.ncbi.nlm.nih.gov/19793855/">less overall</a> – and even <a href="https://pubmed.ncbi.nlm.nih.gov/20815899/">less on the feed days</a> than they did before starting intermittent fasting. This supports the idea that intermittent fasting can lead to <a href="https://www.mdpi.com/2076-328X/7/1/4">comparable weight loss</a> as conventional diets, where you restrict calories daily. </p>
<p>But while these diets may be successful in getting people to eat less, they may actually reinforce bad eating habits and poor diet quality (such as consuming high-energy, highly-processed foods and drinks), as people may think they can “treat” themselves following low-calorie days. Indeed, research has shown people following these diets have a <a href="https://pubmed.ncbi.nlm.nih.gov/30514879/">less nutritious diet</a> than those following traditional calorie-controlled diets. </p>
<p>Other studies have shown that people following the 5:2 diet <a href="https://theconversation.com/intermittent-fasting-if-youre-struggling-to-lose-weight-this-might-be-why-123498">consume more calories</a> before fast days unconsciously – which could very well happen on the metabolic confusion diet, too.</p>
<p>The other reason for the metabolic confusion diet’s popularity is because fans of the diet claim that switching between low- and high-calorie days keeps your metabolism active, causing you to burn more calories as a result. It’s also believed that this “confusion” will stop <a href="https://pubmed.ncbi.nlm.nih.gov/21677272/">biological resistance</a> – such as an increase in appetite – to the diet that may derail weight loss or cause you to regain any weight you’ve lost.</p>
<p>But when we lose weight, our <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5097076/">body needs</a> <a href="https://pubmed.ncbi.nlm.nih.gov/7632212/">fewer calories to survive</a>. These changes to our metabolic rate (the baseline amount of calories our body needs to function daily) can even be seen <a href="https://pubmed.ncbi.nlm.nih.gov/27136388/">several years following weight loss</a>. This is thought to be the result of <a href="https://pubmed.ncbi.nlm.nih.gov/18279786/">body mechanisms</a> that adjust the metabolic rate downwards through a special process (called <a href="https://pubmed.ncbi.nlm.nih.gov/26627218/">adaptive thermogenesis</a>). This process aims to stop energy from being wasted by preserving it in fat tissue and other fuel reserves. Increased appetite is another way the body tries to restore lost body weight.</p>
<figure class="align-center ">
<img alt="A woman looking into her fridge late at night." src="https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373579/original/file-20201208-22-z6opjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Your body will try to prevent you from losing weight.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/rear-view-young-woman-looking-fridge-561901111">Andrey_Popov/ Shutterstock</a></span>
</figcaption>
</figure>
<p>The other key selling point of the metabolic confusion diet is that it prevents your metabolism from slowing as you lose weight. However, when we look at studies on intermittent fasting, we see the <a href="https://www.mdpi.com/2076-328X/7/1/4/htm#B18-behavsci-07-00004">same reduction</a> in resting metabolic rate as <a href="https://pubmed.ncbi.nlm.nih.gov/29508693/">traditional calorie-restricted diets</a> do. </p>
<p>The <a href="https://pubmed.ncbi.nlm.nih.gov/27569118/">odd study</a> that has suggested intermittent fasting raises your metabolic rate can often be explained by the inclusion of total fasting. </p>
<p>Fasting causes an acute <a href="https://pubmed.ncbi.nlm.nih.gov/761706/">metabolic starvation response</a>, leading the body to burn through more of its reserved fuel for around 24-48 hours after a fast. All short-term emergency fuel management measures to glucose supply to the brain. But even in this case, any temporary increase in metabolism may be barely detectable. Also, some studies have actually shown <a href="https://pubmed.ncbi.nlm.nih.gov/28446382/">greater reductions in metabolic rate</a> with intermittent fasting. </p>
<p>The truth is that <a href="https://pubmed.ncbi.nlm.nih.gov/22846776/">no matter how you lose weight</a>, your metabolic rate will decrease. Even certain types of exercise, may not necessarily increase metabolism – with studies on endurance training (such as long-distance running) showing that <a href="https://pubmed.ncbi.nlm.nih.gov/6686116">metabolic rate slows</a> in order to use energy more efficiently during exercise. However, the body does burn more calories immediately after exercise to <a href="https://formnutrition.com/inform/what-is-epoc-and-can-it-impact-post-workout-weight-loss/">help muscles recover</a>, especially after <a href="https://pubmed.ncbi.nlm.nih.gov/32656951/">higher intensity exercise</a>. Regular weight training could potentially lead to a <a href="https://pubmed.ncbi.nlm.nih.gov/32397898/">higher metabolic rate</a>. </p>
<h2>Potential benefits</h2>
<p>But if the metabolic confusion diet functions similarly to intermittent fasting, it may have other benefits beyond just weight loss.</p>
<p>Intermittent periods of energy restriction have been shown to improve <a href="https://pubmed.ncbi.nlm.nih.gov/28091348/">glucose (blood sugar) and lipid (fat) metabolism</a>. This means the body is better able to deal with <a href="https://pubmed.ncbi.nlm.nih.gov/29508693/">carbohydrate and fat from a meal</a>. This makes the body better able to tolerate indulgent foods when we encounter them.</p>
<p>By this token intermittent fasting-type diets can improve your ability to manage fuels in the body – known as <a href="https://pubmed.ncbi.nlm.nih.gov/28467922/">metabolic flexibility</a>. Metabolic flexibility means you’re better at burning and storing carbohydrates when you need to, and equally <a href="https://pubmed.ncbi.nlm.nih.gov/16574156/">better at managing</a> the storage and release of fat from fat stores. This improves insulin sensitivity, which reduces overall risk from disease, such as cardiovascular disease and diabetes. All of this is independent of weight or weight loss. </p>
<p>Although the metabolic confusion diet may be just another fad diet, it may have benefits other than losing weight given it’s similarity to intermittent fasting. While it can’t “speed up” your metabolism, diets that allow us to have more flexibility in the way we eat are more sustainable and easier to follow in the long run.</p><img src="https://counter.theconversation.com/content/150341/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adam Collins does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>This latest fad diet draws many parallels with other intermittent fasting-type diets.Adam Collins, Senior Teaching Fellow, Nutrition, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1410962020-09-08T13:04:13Z2020-09-08T13:04:13ZCalories or macros: nutritionist explains which works best for weight loss or building muscle<figure><img src="https://images.theconversation.com/files/356944/original/file-20200908-14-yazh2e.jpg?ixlib=rb-1.1.0&rect=7%2C7%2C4863%2C3234&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Whether tracking macros or counting calories, you'll need to get used to recording everything you eat and drink daily.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/dieting-calories-control-wellness-woman-using-1225749835">Pormezz/ Shutterstock</a></span></figcaption></figure><p>While reducing calorie intake is a proven way to reduce your weight, there’s no shortage of diets promising the same results but with more flexibility. One such popular diet is “<a href="https://www.healthline.com/nutrition/iifym-guide#:%7E:text=IIFYM%2C%20or%20%E2%80%9CIf%20It%20Fits,namely%20protein%2C%20fat%20and%20carbohydrates.">If It Fits Your Macros</a>” (IIFYM), which offers users less restriction in what they eat, while still guaranteeing results.</p>
<p>Rather than counting calories, IIFYM counts the daily <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4960974/">macronutrients</a> (fats, carbohydrates, and proteins) found in the foods and drinks we consume. Many people like the diet because it offers flexibility and allows them to consume any food as long as it fits into their daily macronutrient (“macro”) requirements.</p>
<p>However, there’s currently no scientific research that has specifically examined whether counting macros is as effective as other methods in achieving different weight goals. Past research has looked into the effects of reducing or manipulating individual macros for weight loss, such as comparing the effect of consuming a <a href="https://examine.com/nutrition/low-fat-vs-low-carb-for-weight-loss/">low-fat versus low-carbohydrate</a> diet or comparing four diets containing different proportions of <a href="https://www.nejm.org/doi/10.1056/NEJMoa0804748">fat, carbohydrate and protein</a>. Ultimately, researchers found no significant, long-term difference between the diets on how much weight they helped people lose) – and all are difficult to adhere to in the long term. </p>
<p>As such, this makes it difficult to know whether counting calories or macros is more useful when it comes to your different body weight goals.</p>
<h2>Weight loss</h2>
<p>The basic principle to achieving weight loss is eat less energy than your body requires on a daily basis and you will lose weight. Any diet can lead to weight loss as long as this basic principle is applied. </p>
<p>The tricky part is establishing what our energy requirements really are. The most practical and accurate measure of this, <a href="https://www.researchgate.net/publication/304339946_Indirect_calorimetry_in_nutritional_therapy_A_position_paper_by_the_ICALIC_study_group">indirect calorimetry</a> (a measurement of the gases that we breathe from which energy expenditure can be estimated), is still not 100% accurate. And the <a href="https://jandonline.org/article/S0002-8223(05)00149-5/abstract">prediction equations</a> commonly used in dietary counselling and by online apps to set calorie intake goals for weight loss are even more inaccurate. This is especially so in those who are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5622772/%20%20">overweight or obese</a> due to the equations being based on body weight, and not taking account of fat mass.</p>
<p>But whether you’re counting calories or macros, you still need this starting point to work from to keep within your targets. While our actual energy requirements are uncertain and can vary greatly depending on how active we are, our <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/618167/government_dietary_recommendations.pdf">requirements for macronutrients</a> are more certain, based on government guidelines.</p>
<p>An advantage of counting macros is that it ensures that some <a href="https://www.nutrition.org.uk/healthyliving/basics/exploring-nutrients.html?limitstart=0">essential nutrients</a> are incorporated into your diet, instead of focusing solely on calories. Counting calories takes no account of nutrients. And while it seems obvious that choosing wholesome nutritious sources of calories is better than processed, high-sugar and saturated fat foods, you could hypothetically eat seven chocolate bars (each worth 228 calories, a total of 1,596 calories) and still lose weight if your total energy expenditure is around 2,000 calories a day.</p>
<p><a href="https://www.calculator.net/macro-calculator.html?ctype=metric&cage=48&csex=f&cheightfeet=5&cheightinch=10&cpound=165&cheightmeter=166&ckg=60&cactivity=1.55&cgoal=m&cmop=0&cformula=m&cfatpct=20&printit=0&x=64&y=16">Macro calculations</a> are estimated based on body weight, height and activity levels and can be adjusted to your weight goal. While fewer restrictions on what to eat may be a bonus for some on IIFYM, for others keeping track of macro intake and hitting those targets can be difficult and time consuming.</p>
<figure class="align-center ">
<img alt="Young woman uses smartphone to track food calories." src="https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/356947/original/file-20200908-18-eujzz5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tracking both macros and calories can be time consuming.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-pretty-woman-using-smart-phone-401552449">RossHelen/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Whatever you’re counting you’ll require an affinity for reading food labels and keeping a record of all foods and fluids consumed throughout the day. While there are numerous online nutritional databases and apps that help you track macros and calories, they may not always be accurate either. Plus there’s the added complication that we may not actually absorb all of the <a href="https://theconversation.com/why-most-food-labels-are-wrong-about-calories-35081#:%7E:text=Your%20body%20gets%20two%2Dthirds,among%20cooked%20foods%2C%20digestibility%20varies.">energy or nutrients</a> that food labels list, making it even harder to meet specific targets.</p>
<p>Additionally, neither method will guarantee that you meet all of your other nutrient requirements. For example, as macros only focus on carbs, protein and fats, they may overlook the importance of other <a href="https://www.nhs.uk/conditions/vitamins-and-minerals/">vitamins and minerals</a>, such as vitamin A, which are essential for staying healthy and preventing deficiencies. Unless combined with dietary advice about making permanent changes to a <a href="https://www.nhs.uk/live-well/eat-well/the-eatwell-guide/">healthy balanced diet</a>, neither method is a long-term solution to weight loss or maintenance.</p>
<h2>Muscle gain</h2>
<p>On the opposite end of the spectrum are people looking to gain weight to build muscle. Someone looking to <a href="https://www.bda.uk.com/resource/sport-exercise-nutrition.html">gain muscle</a> would need to increase their basic daily protein intake to around 1.2-1.7 grams of protein per kilogram of body weight for muscles to repair any micro-damage that occurs from resistance or strength training which is necessary for muscle growth. As well as protein, <a href="https://www.tandfonline.com/doi/full/10.1080/02640414.2011.574722">energy and carbohydrate needs</a> must also be met to ensure the body has enough fuel available to work out. This is where keeping track of macros, instead of counting calories, could be useful to ensure all protein and carbohydrate requirements are met. </p>
<p>Timings of macros are also important for muscle growth. Research shows regular protein intake <a href="https://jissn.biomedcentral.com/articles/10.1186/s12970-018-0215-1">throughout the day</a> and after exercise, rather than large single doses, is recommended for muscle growth and refuelling.</p>
<p>Ultimately, which method you choose for altering body weight and composition depends on your goals and how motivated and tech savvy you are. If you are keen to learn more about the nutrients in the food you are eating then counting macros may be for you. For those who find endless counting and monitoring tedious it may be easier to follow more general guidance for <a href="https://www.bda.uk.com/resource/weight-loss.html">weight loss or maintenance</a> or for <a href="https://www.bda.uk.com/resource/sport-exercise-nutrition.html">bulking up</a>.</p><img src="https://counter.theconversation.com/content/141096/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Kinrade does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Counting macronutrients offers more food flexibility – but may be most useful when trying to build muscle.Emma Kinrade, Lecturer in Nutrition and Dietetics, Glasgow Caledonian UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1431622020-07-24T12:22:17Z2020-07-24T12:22:17ZLove avocados? Thank the toxodon<figure><img src="https://images.theconversation.com/files/349221/original/file-20200723-29-nkn0qn.jpg?ixlib=rb-1.1.0&rect=31%2C7%2C5204%2C3312&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The finicky fruit took some time to adapt to California's climate.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/avocado-groves-san-diego-california-usa-c1900s-published-by-news-photo/463970581?adppopup=true">Print Collector via Getty Images</a></span></figcaption></figure><p>Given avocado’s popularity today, it’s hard to believe that we came close to not having them in our supermarkets at all. </p>
<p>In my book “<a href="https://press.uchicago.edu/ucp/books/book/distributed/A/bo50552476.html">Avocado: A Global History</a>,” I explain how the avocado survived a series of ecological and cultural close calls that could have easily relegated them to extinction or niche delicacy. Instead, the avocado persevered, prospered – and became <a href="https://spoonuniversity.com/lifestyle/the-10-most-instagrammed-foods-and-drinks-of-all-time">one of the most Instagrammed foods in the world</a>.</p>
<h2>A ‘ghost of evolution’</h2>
<p>Avocados are in <a href="https://www.britannica.com/plant/laurel-plant-Laurus-genus">the laurel family</a>, the same group of plants that includes bay leaves and cinnamon. Laurel trees prosper in warm subtropical climates, and the avocado evolved in the warming climates of Central America during the <a href="https://www.nationalgeographic.com/science/prehistoric-world/neogene/">Neogene period</a>, roughly 10 million years ago.</p>
<p>During the Pleistocene era, which followed the Neogene, the biggest animals on Earth were what we call the megaherbivores – giant animals that subsisted almost entirely on a vegetarian diet. Most of these, like <a href="https://www.mentalfloss.com/article/77099/10-big-facts-about-giant-ground-sloths">the giant ground sloth</a>, would have dwarfed today’s largest megaherbivore, the African elephant. The giant herbivores of Pleistocene Mesoamerica like the <a href="https://www.britannica.com/animal/gomphothere">gomphothere</a>, <a href="https://blog.nationalgeographic.org/2014/05/07/diggers-in-the-dark-discovering-giant-armadillos-in-brazils-pantanal/">the giant armadillo</a> and the <a href="https://www.nationalgeographic.com/science/phenomena/2015/03/18/darwins-strangest-beast-finds-place-on-tree/">toxodon</a> needed hundreds of pounds of food a day just to survive. Since food like leaves and grasses are so low in calories and fat, the animals prized any energy dense and fatty foods. </p>
<p>Enter: the avocado.</p>
<p>Megaherbivores didn’t peel the avocados and eat the green meat like we do today. Instead, their throats and digestive tracts were so large that they would simply swallow the avocado whole and excrete the undigested pit. In a process known as <a href="https://doi.org/10.3389/fevo.2019.00265">endozoochory</a>, the pile of manure would serve as food for the next generation of avocado trees. As these giant animals roamed and grazed on avocados, they spread the fruit across what is now central Mexico.</p>
<figure class="align-center ">
<img alt="A toxodon – an extinct animal bigger than an elephant – grazes." src="https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349218/original/file-20200723-21-zlxkam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Megaherbivores like the toxodon were the avocado’s best friend.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/7/71/Toxodon_platensis.jpg">Robert Bruce Horsfall/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>But once the megaherbivores died off, the fruit was in a bind. The herbivores that were left had throats far too small to ingest a whole avocado seed, and dropping a giant seed at your own roots is a poor survival strategy for a tree; to thrive, it needs to disperse more broadly. </p>
<p>Avocados became what the botanist Connie Barlow calls a “<a href="http://arnoldia.arboretum.harvard.edu/pdf/articles/2001-61-2-anachronistic-fruits-and-the-ghosts-who-haunt-them.pdf">Ghost of Evolution</a>” – a species that should have gone extinct but was somehow able to survive. What the avocado had going for it was the lifespan of its trees, which survive much longer than most fruit trees. There are 100-year-old trees still producing fruit in California and 400-year-old trees in central Mexico.</p>
<p>By living so long and being so well adapted to their ecological niche, avocados were able to hold on until their next dispersers – <em>Homo sapiens</em> – came along.</p>
<h2>More stops and starts</h2>
<p>The earliest humans in Mesoamerica were quick to appreciate the virtues of the avocado. Groups like the Olmecs and the Maya started the first avocado orchards and began cultivating specimens that tasted the best and had the meatiest fruits, a process of trait selection that gave us the kinds of avocados we love today. Avocados were so important to the Maya that <a href="https://ancientmayalife.blogspot.com/2018/01/avocados-and-ancient-maya.html">the 14th month of their calendar was named for them</a>.</p>
<p>In the 1830s, Floridian <a href="https://fsi.colostate.edu/avocados/">Dr. Henry Perrine</a> was introduced to avocados while serving as U.S. consul in Campeche, Mexico, and thought they would be an excellent addition to Florida’s horticultural offerings. </p>
<p>He sent some seeds to a friend on Indian Key in Florida who planted them. Not long after Perrine returned, the Second Seminole War <a href="https://www.seminolenationmuseum.org/history/seminole-nation/the-seminole-wars/">broke out</a>. Perrine and his family sought shelter from the fighting on the key, but he was killed during a raid on the island by one of the warring factions. The island was abandoned and the avocado trees were forgotten.</p>
<p>Hot and humid Florida had been hospitable to the avocado, but California has enough cold snaps in the winter months to make it difficult for most avocado varieties to thrive there. This could have been another dead end for the fruit, but early settlers in California took another stab at establishing them in the U.S. After a few failed attempts in the 1850s and 1860s, grower <a href="https://www.californiaavocado.com/avocado101/the-california-difference/avocado-history">Judge R. B. Ord obtained a few cold-hardy specimens from central Mexico</a>. A cold-tolerant variety was needed if California was to have a profitable avocado industry. Without it, the avocado might have remained a delicacy local to Mexico and its neighbors.</p>
<p>One of the earliest cold-hardy specimens was a variety given the name “<a href="http://www.lauriemeadows.info/food_garden/fruit/Avocado_cv_Fuerte.html">Fuerte</a>,” which means “strong” in Spanish. The Fuerte avocado earned its name because it was one of the few varieties that survived the famous “<a href="https://www.redlandsdailyfacts.com/2007/01/28/the-1913-freeze-the-first-and-the-worst-for-redlands/">Freeze of ‘13</a>,” a spell of cold weather that nearly ruined the nascent fruit industries of Southern California in the winter of 1913.</p>
<p>Until the 1940s, the Fuerte was the most popular avocado variety in America and made up about <a href="https://www.kcrw.com/culture/shows/good-food/the-rise-and-fall-of-the-fuerte-avocado">75% of avocados sold</a>.</p>
<h2>The Hass comes to pass</h2>
<p>The Fuerte has since been relegated to niche product, <a href="https://www.specialtyproduce.com/produce/Fuerte_Avocados_6723.php#:%7E:text=The%20Fuerte%20avocado%20is%20the,standard%20for%20judging%20other%20varieties">and represent only about 2% of the California market</a>. Instead, the lion’s share of avocados sold today are the variety known as Hass, which rhymes with “pass.” </p>
<p>But were it not for a couple of kids with precocious palates, the world may never have tasted a Hass avocado, with the fruit remaining an odd delicacy for the well-to-do. </p>
<p>The Hass avocado is named for <a href="https://www.cooksinfo.com/rudolph-hass">Rudolph Hass</a>, a mailman who lived in La Habra, California. Originally from Milwaukee, Hass <a href="https://depts.washington.edu/moving1/dustbowl_migration.shtml">joined the thousands of Americans who went west to California</a> in the 1920s and 1930s. </p>
<p>After reading a brochure about the money to be made in avocado ranching, he borrowed enough money to buy a small plot of land with Fuerte avocado trees on it. In the late 1920s, Hass bought some avocado seeds to grow rootstock for his budding nursery. One of these seeds grew a funny tree that rejected the Fuerte limbs that Hass wanted to <a href="https://www.thespruce.com/what-does-grafting-mean-4125565">graft</a> onto it – a process that involves combining two tree plants with distinct characteristics. He was about to cut the misbehaving tree out, but his kids told him that these odd little avocados were their favorites, so he relented and kept the tree. After trying them himself, he thought they had marketing potential and began selling them to people at work and at a market in town.</p>
<p>Hass avocados slowly caught on, and in 1935 Hass patented the tree, <a href="https://themindcircle.com/the-hass-avocado-mother-tree/">the first patent awarded for a tree in America</a>. But most growers, instead of buying his tree, evaded his patent and simply grafted their cuttings themselves. This practice was illegal, but enforcement in the 1930s was spotty. </p>
<figure class="align-center ">
<img alt="A race car detailed with an advertisement for the Hass avocado." src="https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349219/original/file-20200723-23-132x6x1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Hass avocado is everywhere – but its creator never cashed in.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/dave-blaney-driver-of-the-hass-avocados-from-mexico-news-photo/71455094?adppopup=true">Jamie Squire/Getty Images</a></span>
</figcaption>
</figure>
<p>Today, Americans eat <a href="https://www.verobc.com/avocado-consumption-on-super-bowl-day/">100 million pounds</a> <a href="https://www.bloomberg.com/news/articles/2020-01-30/super-bowl-plans-spur-record-avocado-imports-by-u-s-from-mexico">of avocados</a> on Super Bowl Sunday, and Hass should have died a rich man. Instead, he never earned enough to quit the post office. It’s estimated that <a href="https://www.dailynews.com/2017/07/02/gardening-hass-avocado-patent-didnt-earn-rudolph-hass-as-much-as-he-hoped/">he only made about US$5,000</a> on the patent in his lifetime.</p><img src="https://counter.theconversation.com/content/143162/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jeffrey Miller does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If it weren’t for historical and biological happenstance, few would be eating avocados today.Jeffrey Miller, Associate Professor of Hospitality Management, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1401502020-06-09T12:05:11Z2020-06-09T12:05:11ZWeight loss: here’s why those last few pounds can be hardest to lose – according to science<figure><img src="https://images.theconversation.com/files/340385/original/file-20200608-176571-19id8u7.jpg?ixlib=rb-1.1.0&rect=10%2C0%2C6699%2C4476&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Here's why your progress may have stalled.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/flat-lay-composition-scales-healthy-food-1292487769">New Africa/ Shutterstock</a></span></figcaption></figure><p>So you’ve done everything you’re supposed to. You’re eating in a calorie deficit, are exercising a few times a week, and are getting close to your weight loss goal. And then you hit a plateau with only a few pounds to lose – and they just won’t seem to budge.</p>
<p>It’s long been a complaint that those last five pounds can often be the hardest to lose. And the answer to why this is the case reveals a lot about the dynamic relationship between body weight and appetite (what we feel when we say we’re “hungry”), and about how, as humans, we’re almost always “ready to eat”.</p>
<p>When dieting to lose weight, there are two basic reasons why weight loss typically slows down over time. The first reason is that calorie (energy) expenditure decreases with weight loss. This “<a href="https://pubmed.ncbi.nlm.nih.gov/21872751/">slowed metabolism</a>” happens because fewer calories are required to maintain and move a lighter body. </p>
<p>We can even estimate with reasonable accuracy how <a href="https://pubmed.ncbi.nlm.nih.gov/21872751/">calorie expenditure changes</a> according to weight. For example, a 175-centimetre-tall, moderately active 45-year-old man who weighs 90 kilograms would need to <a href="https://www.niddk.nih.gov/bwp">reduce his calorie intake</a> from 3,200 to 2,270 kcal a day to lose 15 kilograms in six months. It’s worth noting that what we normally call “calories” are actually kilocalories or kcal, which is equal to 1,000 calories.</p>
<p>If he stuck to this diet of 2,270 kcal a day throughout, he would lose on average 2.6 kilograms a month during the first five months and 1.8 kilograms in the final month. He’d then need to eat around 2,780 kcal daily to maintain his goal weight of 75 kilograms.</p>
<p>The second reason why losing weight becomes progressively difficult is that weight loss is accompanied by an <a href="https://pubmed.ncbi.nlm.nih.gov/27059321/">increase in appetite</a>. The hormone leptin tells our brain how much fat is stored in our body. When we have more fat stored, leptin increases and reduces appetite. But when we lose body fat, the leptin <a href="https://pubmed.ncbi.nlm.nih.gov/27059321/">“brake” on our appetite</a> is partly released, <a href="https://pubmed.ncbi.nlm.nih.gov/28202588/">making us a little more hungry</a>.</p>
<p>Changes in calorie expenditure and the effect of body fat stores on appetite both stabilise body weight over the long term. But their effects are barely noticeable in the short term. Instead, at any point in the day the dominant influence on our appetite is how long ago we last ate and how full we still feel from our last meal. In other words, we get hungry when our <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/nbu.12237">stomach tells our brain</a> that it’s empty, or nearly empty.</p>
<h2>Ready to eat</h2>
<p>Left unchecked, signals from our stomach leave us vulnerable to overeating. This is because our stomach has the capacity to accommodate more calories than we expend. For example, a recent study found that when participants were served pizza for lunch and invited to eat until they felt “comfortably full”, they ate 1,580 kcal. When they were asked to eat as much as they could, they ate <a href="https://pubmed.ncbi.nlm.nih.gov/32248846/">twice that amount</a> – their daily calorie requirement in a single meal. This shows that we are almost always ready to eat – and capable of eating beyond a level of comfortable fullness.</p>
<p>Fullness is determined partly by the fat, carbohydrate and protein content of the meal, and partly by its overall bulk. For example, if the meal <a href="https://pubmed.ncbi.nlm.nih.gov/28724643/">contains more fibre</a>, it’s more filling – which is why it’s hard to overeat bulky foods such as fruits and vegetables.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/340386/original/file-20200608-176580-aekcms.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We naturally prefer higher energy-dense foods, like pizza.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/juicy-slice-pizza-being-served-1724874964">Zui01/ Shutterstock</a></span>
</figcaption>
</figure>
<p>If the study’s participants had been offered apples instead, they wouldn’t have been able to eat 1,580 kcal, let alone twice that amount. Because the concentration of calories in apples (their energy density) is only 50 kcal per 100 grams, they would need to eat over three kilograms of apples to eat 1,580 kcal. Pizza has around 280 kcal per 100 grams – over five times higher than the energy density of apples. Fullness per calorie is higher for foods that have a lower energy density. So, we’d feel more full if we ate the same number of calories from apples than pizza. </p>
<p>But we generally find foods that have a high energy density, like pizza (and chocolate and crisps - each over 500 kcal per 100 grams) <a href="https://pubmed.ncbi.nlm.nih.gov/29038018/">more delicious</a>. Biologically, this is probably because these foods are a valuable resource – their low fullness per calorie means we can eat more. So we’re prone to overeat high-calorie foods for two reasons: they’re less filling per calorie, and they’re more delicious (and pleasurable) to eat. But recent research shows that high-calorie foods often don’t <a href="https://pubmed.ncbi.nlm.nih.gov/29038018/">give us that much more pleasure</a> when we eat them. This should make it possible to reduce calorie intake without significantly affecting pleasure. </p>
<p>For example, choosing to eat 100 grams of strawberry yoghurt (95 kcal) instead 100 grams of strawberry cheesecake (at least 250 kcal) may be less pleasurable – but only slightly. With repetition, you may find yourself choosing the lower calorie option out of habit – and keeping your weight in check.</p>
<p>But over time, eating less can be difficult. It’s hard to maintain vigilance and restraint to resist our desire to eat delicious, higher energy-dense foods. Dieting lapses are therefore inevitable, and over time our <a href="https://pubmed.ncbi.nlm.nih.gov/10343341/">motivation to maintain eating restraint</a> and increase physical activity may weaken. This can add further to the perception that the last five pounds is harder to lose.</p>
<p>Overall, our weight settles around a point that is a balance between the lure of the foods that we include in our diet, our eating restraint, and the energy we expend in physical activity. We can change all three, although choosing foods with lower energy density may be an especially effective strategy to reduce weight. And for maintaining that healthier weight, it is worth keeping in mind that lighter bodies require fewer calories.</p><img src="https://counter.theconversation.com/content/140150/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Rogers has received funding from the Biological and Biotechnological Sciences Research Council (research funding), and Sugar Nutrition UK (research funding). Peter Rogers has provided consultancy services for Coca-Cola Great Britain and Lucozade Ribena Suntory. Peter Rogers is a member of the British Nutrition Foundation scientific advisory committee
</span></em></p>Don’t give up just yet.Peter Rogers, Professor of Biological Psychology, University of BristolLicensed as Creative Commons – attribution, no derivatives.