tag:theconversation.com,2011:/us/topics/glycogen-37045/articlesGlycogen – The Conversation2022-05-19T12:23:24Ztag:theconversation.com,2011:article/1794542022-05-19T12:23:24Z2022-05-19T12:23:24ZIs intermittent fasting the diet for you? Here’s what the science says<figure><img src="https://images.theconversation.com/files/453968/original/file-20220323-23-zm8qqm.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Intermittent fasting could have an array of health benefits, but as of yet there are no long-term studies into its effects.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/intermitted-farsting-diet-concept-royalty-free-image/1361961784?adppopup=true">neirfy/iStock via Getty Images Plus</a></span></figcaption></figure><p>What if I told you all you need to do to lose weight is read a calendar and tell time? These are the basics for successfully following an intermittent fasting diet. </p>
<p>Can it be that simple, though? Does it work? And what is the scientific basis for fasting? As a registered dietitian and <a href="https://experts.okstate.edu/mckale.montgomery">expert in human nutrition and metabolism</a>, I am frequently asked such questions.</p>
<p>Simply stated, intermittent fasting is defined by alternating set periods of fasting with periods in which eating is permitted. One method is <a href="https://doi.org/10.1093/ajcn/86.1.7">alternate-day fasting</a>. On “fast days,” followers of this form of fasting are restricted to consuming no more than 500 calories per day; on “feast days,” which occur every other day, they can eat freely, with no restrictions on the types or quantities of foods eaten. </p>
<p>Other methods include the increasingly popular <a href="https://doi.org/10.1038/s41574-022-00638-x">5:2 method</a>. This form of fasting involves five days of feasting and two days of fasting per week. </p>
<p>Another variation relies on time-restricted eating. That means followers should fast for a specified number of hours – typically 16 to 20 per day – while freely consuming foods within a designated four- to eight-hour period.</p>
<p>But what about eating breakfast and <a href="https://doi.org/10.1056/NEJM198910053211403">then small meals throughout</a> the day to keep the body’s metabolism running? After all, that’s the <a href="https://doi.org/10.1093/ajcn/81.1.16">conventional wisdom</a> that many of us grew up with. </p>
<p>To answer these questions, it helps to understand the basics of human metabolism. </p>
<figure>
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<figcaption><span class="caption">A TV host went on a two-month intermittent fast to lose weight. Did it work?</span></figcaption>
</figure>
<h2>Human metabolism 101</h2>
<p>The human body requires a continual supply of energy to sustain life, and the foods we eat provide us with this energy. But because eating is often followed by periods of time without eating, an intricate set of biological pathways is in place to meet the body’s energy demands between meals. </p>
<p>Most of the pathways function at some level all the time, but they fluctuate following a meal in a predictable pattern called the <a href="https://doi.org/10.1007/s13679-018-0308-9">fed-fast cycle</a>. The time frames of the cycle can vary, depending on the food types eaten, the size of the meal and the person’s activity level.</p>
<p>So what happens, metabolically speaking, after we eat? Consuming carbohydrates and fats leads to a rise in blood glucose and also <a href="https://doi.org/10.1001/jama.2013.280593">lipid levels</a>, which include cholesterol and triglycerides. </p>
<p>This triggers the release of insulin from the pancreas. The insulin helps tissues throughout the body take up the glucose and lipids, which supplies the tissues with energy. </p>
<p>Once energy needs are met, leftover glucose is stored in the liver and skeletal muscle in a condensed form called glycogen. When glycogen stores are full, excess glucose converts to fatty acids and is stored in fat tissue. </p>
<p><a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/absorptive-state">About three to 18 hours</a> after a meal – again, depending upon a person’s activity level and size the of the meal – the amount of circulating blood glucose and lipids returns to baseline levels. So tissues then must rely on fuel sources already in the body, which are the glycogen and fat. A hormone called glucagon, secreted by the pancreas, helps facilitate the breakdown of glycogen and fat to provide energy for the body between meals. </p>
<p>Glucagon also initiates a process known as <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/gluconeogenesis">gluconeogenesis</a>, which is the synthesis of glucose from nondietary sources. This helps maintain the right level of blood glucose levels.</p>
<p>When the body reaches a true fasting state – about 18 hours to two days without additional food intake – the body’s stores of glycogen are depleted, and tissues like the heart and skeletal muscle start to rely heavily on fats for energy. That means an increase in the breakdown of the stored fats. </p>
<p>“Aha!” you might say. “So intermittent fasting is the key to ultimate fat burning?” Well, it’s not that simple. Let’s go through what happens next.</p>
<h2>The starvation state</h2>
<p>Though many tissues adapt to using fats for energy, the brain and red blood cells need a continual supply of glucose. But when glucose is not available because of fasting, the body starts to break down its own proteins and <a href="https://doi.org/10.1152/ajpendo.1997.273.6.E1209">converts them to glucose instead</a>. However, because proteins are also critical for supporting essential bodily functions, this is not a sustainable process.</p>
<p>When the body enters the starvation state, the body goes into self-preservation mode, and a metabolic shift occurs in an effort to spare body protein. The body continues to synthesize glucose for those cells and tissue that absolutely need it, but the breakdown of stored fats increases as well to provide energy for tissues such as the skeletal muscle, heart, liver and kidneys. </p>
<p>This also <a href="https://www.ncbi.nlm.nih.gov/books/NBK493179/#">promotes ketogenesis</a>, or the formation of ketone bodies – molecules produced in the liver as an energy source when glucose is not available. In the starvation state, ketone bodies are important energy sources, because the body is not capable of solely utilizing fat for energy. This is why it is inaccurate when some proponents of intermittent fasting claim that fasting is a way of burning “just fat” - it’s not biologically possible.</p>
<p>What happens when you break the fast? The cycle starts over. Blood glucose and lipids return to basal levels, and energy levels in the body are seamlessly maintained by transitioning between the metabolic pathways described earlier. The neat thing is, we don’t even have to think about it. The body is well-equipped to adapt between periods of feasting and fasting. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/G5J6BfFMZPM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Intermittent fasting – fact or fiction? What the science actually says.</span></figcaption>
</figure>
<h2>Possible downsides</h2>
<p>If an “all-or-nothing” dietary approach to weight loss sounds appealing to you, chances are it just might work. Indeed, intermittent fasting diets have produced <a href="https://doi.org/10.1001/jamainternmed.2017.0936">clinically significant</a> amounts of weight loss. Intermittent fasting may also <a href="https://doi.org/10.1038/s41574-022-00638-x">reduce disease risk</a> by lowering blood pressure and blood lipid levels.</p>
<p>On the flip side, numerous studies have shown that the weight reduction from intermittent fasting diets is <a href="https://doi.org/10.1001/jamainternmed.2017.0936">no greater than</a> the weight loss on a standard calorie-restricted diet.</p>
<p>In fact, the weight loss caused by intermittent fasting is due not to spending time in some sort of magic metabolic window, but rather to reduced overall calorie consumption. On feast days, dieters do not typically <a href="https://doi.org/10.1186/1475-2891-9-35">fully compensate</a> for lack of food on fasted days. This is what results in mild to moderate weight loss. Approximately 75% of the weight is fat mass; the rest is lean mass. That’s about the <a href="https://doi.org/10.1038/s41574-022-00638-x">same ratio as a standard low-calorie diet</a>.</p>
<p>Should you still want to go forward with intermittent fasting, keep a few things to keep in mind. First, there are no studies on the long-term safety and efficacy of following this type of diet. Second, studies show that intermittent fasters don’t get enough of <a href="https://doi.org/10.1016/j.clnu.2020.02.022">certain nutrients</a>. </p>
<p>Exercise is something else to consider. It helps preserve lean muscle mass and may also contribute to increased weight loss and long-term weight maintenance. This is important, because nearly a quarter of the weight lost on any diet is muscle tissue, and the efficacy of intermittent fasting for weight loss has been demonstrated <a href="https://doi.org/10.1038/s41574-022-00638-x">for only short durations</a>.</p>
<p>Also, once you stop following an intermittent-fasting diet, you will very likely gain the weight back. This is a critical consideration, because many people find the diet difficult to follow long-term. Imagine the challenge of planning six months’ worth of feasting and fasting around family dinners, holidays and parties. Then imagine doing it for a lifetime. </p>
<p>Ultimately, the best approach is to follow an eating plan that meets current dietary recommendations and fits into your lifestyle.</p><img src="https://counter.theconversation.com/content/179454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>McKale Montgomery receives funding from the National Institutes of Health.</span></em></p>Proponents of intermittent fasting say the clock can help you win the battle of the bulge. But the science behind it is a little more complicated.McKale Montgomery, Assistant Professor of Nutritional Sciences, Oklahoma State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1796292022-04-13T12:13:29Z2022-04-13T12:13:29ZHow math – and eating while running – can help you complete your best marathon<figure><img src="https://images.theconversation.com/files/457489/original/file-20220411-17-v4whu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Long-distance running requires planning, from pacing to stoking the body's engines.</span> <span class="attribution"><span class="source">Nick Morgan</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Whether standing at the starting line for a high school cross-country competition or, years later, at the cold rainy 2018 Boston Marathon, I have always been nervous before races. </p>
<p>In November 2021, I was again at the starting line, this time at the Monumental Marathon in Indianapolis. And while I’ve always prepared for a race, this time I did it differently.</p>
<p>I’d spent the previous three years doing scientific research as part of my doctoral program at the University of Tennessee, Knoxville, showing, mathematically, how to use nutrition and training to run an optimal race.</p>
<p>While there is significant research on pacing, training and eating, there has been little research done at the intersection of math and running. The research that has been done focuses mainly on <a href="https://doi.org/10.1137/090749384">shorter races, like the 800-meter</a>, instead of longer distances, and none of it focuses on the practice of eating while running. I wanted to find out how a marathon runner could maximize energy output to run the fastest possible race. </p>
<p>My colleagues <a href="https://math.utk.edu/people/Suzanne-Lenhart/">Suzanne Lenhart</a>, <a href="https://nutrition.utk.edu/guoxun-chen-phd-lab/">Guoxun Chen</a> and <a href="https://people.clas.ufl.edu/hager/">William Hager</a> and I combined mathematics with research from the worlds of nutrition and sports science to identify how a runner’s speed should change throughout a race – and how much and when to eat during the run. </p>
<h2>Marathon performance</h2>
<p>The marathon emerged from <a href="https://theconversation.com/the-uncertain-origins-of-the-modern-marathon-79493">an ancient Greek legend</a> of Pheidippides, a messenger who ran 40 kilometers from Marathon to Athens in 490 B.C. to bring news about a Persian invasion – or possibly, to announce the Athenians’ victory. </p>
<p>More than 2,000 years later, in 1896, the <a href="https://www.history.com/this-day-in-history/first-modern-olympic-games">first modern Olympics</a> included a marathon. The next year, the <a href="https://www.baa.org/races/boston-marathon/history">first Boston Marathon</a> was held. The race, likely the most famous of more than 1,100 marathons organized in the U.S. each year, will mark its 126th anniversary on April 18.</p>
<p>Completing a 26.2-mile marathon requires both training and strategy. Pacing is key: A runner who takes off at a sprint can’t expect to maintain that speed. In the 1920s, runners first realized the need to <a href="https://doi.org/10.1093/nutrit/nuy001">stoke energy</a> during long-distance runs and began sucking on hard candies during races. Today, a lucrative industry sells energy gels, gummies, sports drinks and other in-race nutritional products. </p>
<p>That’s because running is an <a href="https://doi.org/10.1016/bs.pmbts.2015.07.020">energy game</a>, fueled by stored fat and glycogen. During high exertion, the body <a href="https://doi.org/10.1152/japplphysiol.91394.2008">burns mainly glycogen</a>, a complex carbohydrate structure used to store energy in the muscles and liver. </p>
<p>That’s where nutrition planning comes in. The body has plenty of stored fat, but a limited supply of <a href="https://runningmagazine.ca/sections/training/how-to-avoid-hitting-the-wall/">glycogen</a>, enough to run maybe 15 miles. Eating carbohydrate-loaded meals leading up to a race builds <a href="https://academic.oup.com/nutritionreviews/article/76/4/243/4851715">glycogen stores</a>. </p>
<p>But high-speed or long-distance running can exhaust available glycogen, triggering a miserable and well-known experience known as “bonking” or “hitting the wall.” When the body runs out of sugar to burn, muscles cramp up and, in extreme cases, a runner may experience dizziness or confusion, or may even collapse. The antidote: consuming simple sugar during a race.</p>
<h2>Modeling racing biology</h2>
<p>To show scientifically how to <a href="https://doi.org/10.1063/1.3128231">run the fastest possible race</a>, my colleagues and I built a computer model. It relies on various <a href="https://gccoaching.fit/2019/02/18/breaking-down-ftp-vla-max-vs-vo2-max/">personal parameters</a> such as a runner’s weight and ability to absorb oxygen, which is calculated by most sports watches.</p>
<p>Other factors include the rate at which a runner burns calories and how quickly the body clears lactate, a compound that makes the muscles feel heavy when it accumulates. We incorporated equations for speed; changes in available energy from fat and glycogen; and the energy boost from food consumed during the race. </p>
<p>Then we programmed in our goal: determining how a simulated marathoner can run the most efficient 26.2-mile race. </p>
<p>We evaluated various combinations of speed and available energy alongside fuel intake, ranging from 100 to 1,100 calories. Overall, our model shows that maintaining a fairly constant speed from start to finish helps a runner achieve top performance. </p>
<p>The results differ significantly from person to person. The model reveals an individual’s best speed and calculates the amount of calories they should take in, based on personal needs, and when to consume them. The model also generates graphs to visually depict results. All can be improved with dedicated training, making a runner more energy efficient.</p>
<h2>Optimizing performance</h2>
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<figcaption><span class="caption">Legendary marathon runner Eliud Kipchoge of Kenya made world history with his 2019 run in Austria.</span></figcaption>
</figure>
<p>Since this model is based on biological phenomena, not data, we needed to validate the approach. So we compared a simulation of <a href="https://www.nytimes.com/2019/10/12/sports/eliud-kipchoge-marathon-record.html">Eliud Kipchoge’s 2019 world record-breaking marathon</a> against his actual performance. Kipchoge, the first to ever complete a marathon in under two hours – <a href="https://www.ineos159challenge.com/">1:59:40</a> – gave an amazing physical performance that was optimized by a team of experts. </p>
<p>To compare our simulation with his actual race, we put in his personal parameters alongside the 800 calories he consumed. Our model proved extremely accurate: The simulation differed from Kipchoge’s performance by just one second per mile.</p>
<p>I then used myself to test our model on a runner with a different skill level. I stood on the starting line of the Indianapolis Marathon, prepared to use the model’s pacing strategy and in-race nutrition plan to consume five 100-calorie gels. I finished in 2:37:14, a major personal best for me, more than 15 minutes faster than I’d ever run. The simulation again proved strong: It differed from my true race time by less than 1%.</p>
<p>The ultimate goal of this work is to create a user-friendly application that allows runners to plan in-race nutrition and calculate their best speed, both of which are crucial to running the optimal marathon. </p>
<p>[<em>Get fascinating science, health and technology news.</em> <a href="https://memberservices.theconversation.com/newsletters/?nl=science&source=inline-science-fascinating">Sign up for The Conversation’s weekly science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/179629/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Cook 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>What is the best strategy for running your best race? A new computer model might soon join your training team.Cameron Cook, PhD graduate, researcher, University of TennesseeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/741612017-04-20T19:51:48Z2017-04-20T19:51:48ZWhy terms like ‘shred, burn and melt’ belong in the kitchen, not the gym<figure><img src="https://images.theconversation.com/files/161914/original/image-20170322-5386-i21hdn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Unlike the immediacy of cooking, gaining and losing fat are relatively slow processes. Rapid methods for weight loss are rarely sustainable. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/552913873?src=ds2cijC6XWEgX_pDcVOyjg-1-16&size=huge_jpg">from www.shutterstock.com </a></span></figcaption></figure><p>Celebrity trainers and buff social media stars use terms such as “shred”, “burn” and “melt” to describe bodies responding to resistance training and cardiovascular exercise with rapid physical transformation. </p>
<p>In the kitchen, shredding a carrot takes just a few minutes and results in destruction of a solid into small, manageable parts. Burning involves heat and occasionally pain, and can occur in just seconds (especially if you turn your back). Solid fats melt into liquids that can be drained away. </p>
<p>But do these terms actually describe what’s going on when we exercise? A simple analysis of how our body uses, stores and mobilises energy says no, they don’t. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=558&fit=crop&dpr=1 754w, https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=558&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/162851/original/image-20170328-21232-15w1d39.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=558&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tags like #shred, #timetogrind and #workhard suggest your new body is just around the corner.</span>
<span class="attribution"><span class="source">be_more_athletics/Instagram</span></span>
</figcaption>
</figure>
<h2>The currency of immediate energy</h2>
<p>When we have a meal, the gut breaks down the food into carbohydrates, lipids (fats) and protein, which are released into the blood stream. </p>
<p>For immediate energy requirements, our bodies use multiple biochemical pathways to convert these components into a <a href="http://onlinelibrary.wiley.com/doi/10.1002/cphy.c110007/abstract">high energy compound known as ATP</a> (adenosine triphosphate). The energy released is used to keep us awake, sustain breathing, work our brains and for some physical exercise. </p>
<p>In a sense, ATP is the “currency” the body uses to complete daily bodily functions and physical tasks. In its ready-to-be-traded-for-energy form, the total amount of ATP stored in cells at any given time only lasts <a href="http://www.jbc.org/content/240/10/3996.long">about two seconds</a>. </p>
<p>The rate of ATP production is <a href="https://www.ncbi.nlm.nih.gov/pubmed/6342340">adjusted constantly</a> to the amount of energy we require at any given time. For example, when we are asleep we require less ATP than when we are in the middle of a workout on a treadmill or using weights. </p>
<p>So what happens if we have a meal and don’t require a lot of energy in the short term? Rather than the meal being converted into ATP, it is transformed into stored energy inside our body for later use. </p>
<h2>Energy stored for use later</h2>
<p>While our body doesn’t store a large amount of ATP, it does store nutrients away from the bloodstream so that we can access them in between meals and during the fasting hours at night time. When energy demands increase through exercise, we use these stored nutrients to respond. </p>
<p>Proteins are mainly used as building blocks for skeletal muscle, hormones and other compounds. Proteins only provide <a href="http://journals.lww.com/acsm-msse/pages/articleviewer.aspx?year=1987&issue=10001&article=00013&type=abstract">around 5% of energy</a> required for exercise. </p>
<p>Carbohydrates are stored in the form of a complex molecule called <a href="http://jap.physiology.org/content/64/4/1480.long">glycogen</a> in skeletal muscles and the liver. </p>
<p>Molecules known as free fatty acids are created from dietary fats, and are <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7793.2001.00295.x/abstract">converted and stored as fat</a> throughout the body if not immediately used. But body fat doesn’t just come from dietary fat: once we reach the maximum storage capacity for glycogen (carbohydrates), we <a href="http://ajcn.nutrition.org/content/48/2/240.abstract">convert the excess carbohydrates</a> into body fat too. </p>
<p>Why do we tend to accumulate fat around our bodies so easily? Because it’s the most effective way to store energy, providing <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7793.2001.00295.x/full">10-15 times the amount of energy</a> as glycogen. Accumulation of body fat can be substantial, and often higher than we might like for optimal health.</p>
<h2>What do we use when we exercise?</h2>
<p>During exercise, 95% of the energy we use comes from glycogen and body fat, and the <a href="https://www.ncbi.nlm.nih.gov/pubmed/9781322">proportion of each</a> depends on the intensity of exercise. </p>
<p>Carbohydrates stored as glycogen offer a medium term source of energy: these can be mobilised to service approximately <a href="http://ajpendo.physiology.org/content/275/2/E332.long">two hours of high intensity exercise</a>. Glycogen is the type of stored energy you use if you run a short to middle distance race at full pace - it’s the source of energy for what’s called “anaerobic exercise”. </p>
<p>The lower the exercise intensity, the <a href="http://ajpendo.physiology.org/content/267/6/E934">higher the percentage of lipids</a> we use to fuel the exercise. Relatively easy but sustained workouts will use fat as a primary source of energy. Body fats provide almost unlimited energy for weeks or even months. The best way to lose fat accumulated around the body is to engage in frequent, sustained and low intensity exercise. This type of exercise is called “aerobic exercise”. </p>
<p>Regardless of how much fat we store and use for energy, the number of fat cells (also referred to as adipocytes) in our body remains stable. Greater fat storage simply increases the size of each fat cell. When you lose weight, each fat cell shrinks.</p>
<p>Similarly, when we build muscle bulk by lifting weights, we simply increase the size of each skeletal muscle cell. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=441&fit=crop&dpr=1 600w, https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=441&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=441&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/162852/original/image-20170328-21267-138hb6k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&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 booty day! #feeltheburn.</span>
<span class="attribution"><span class="source">nochtlii/Instagram</span></span>
</figcaption>
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<h2>A lifetime approach</h2>
<p>Although getting rid of fat is a long process, the process of gaining it is also relatively slow. The science of how we use stored energy means that if you want to sustainably lose weight, there are no short-cuts. A lifestyle change in which you commit to engaging in exercise over the long-term is the best approach. </p>
<p>So how do some diets promise to lose fat in barely days or a few weeks? It’s a misconception - what you are losing in most cases is water through dehydration, and in some cases muscle mass, but rarely fat. In most of these cases, lost weight is regained rapidly. </p>
<p>It is <a href="http://ajpendo.physiology.org/content/267/6/E934">metabolically impossible</a> to lose a high amount of fat in a very short period of time, unless you exercise four to six hours every day. </p>
<p>To maintain an appropriate weight after losing any excess and reaching your optimal body mass, you should balance energy intake with energy output. It is that simple: you need to use up the energy equivalent of what you are eating. </p>
<p>The good news is that any type of physical activity is useful to keep this balance in check: circuit-classes, gym work, team sports, yoga, running, golf, gardening, cycling, walking and more. The main goal is to engage in some form of activity and to maintain a relatively healthy and appropriate amount of energy intake. </p>
<p>Burning, melting and and shredding are weight loss marketing terms that don’t accurately describe how our bodies respond to exercise over the short and long term. </p>
<p>A focus on ingesting macro and micronutrients in the same amounts as you convert them into energy for bodily functions and daily routines will help you avoid storing nutrients as excess body fat.</p><img src="https://counter.theconversation.com/content/74161/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Naroa Etxebarria 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>Celebrity fitness gurus tell us to turn up the heat in the gym to see immediate results. But the science of how we use energy in our bodies shows a long-term view is the best approach.Naroa Etxebarria, Assistant Professor Sport and Exercise Science, University of CanberraLicensed as Creative Commons – attribution, no derivatives.