tag:theconversation.com,2011:/africa/topics/low-carbs-8770/articlesLow-carbs – The Conversation2021-01-11T11:18:26Ztag:theconversation.com,2011:article/1517312021-01-11T11:18:26Z2021-01-11T11:18:26ZLow-carb, no sugar, no fat: the fad diets popular in the 20th century<figure><img src="https://images.theconversation.com/files/377778/original/file-20210108-19-qg3ppg.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5000%2C3794&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Bon appétit.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/hands-cutleries-setting-plate-fork-knife-760413733">alex74/ Shutterstock</a></span></figcaption></figure><p>Fad diets certainly aren’t a 21st-century obsession. In fact, they were also a popular way for people throughout the 20th century to slim down and improve their health. Though much has changed since then – including what we know about dieting and weight loss – many of the popular fad diets we follow today share similarities with those followed in the 20th century.</p>
<h2>The early 1900s</h2>
<p><a href="https://academic.oup.com/shm/article/29/4/757/2660184">Regulating body weight</a> became a significant concern in the 1900s, thanks to emerging evidence about the links between obesity and mortality. Like many diets today, early 20th-century diets emphasised low-carb and no sugar.</p>
<p>One of the most popular diets in the early 1900s was the <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.1550-8528.1993.tb00605.x">Banting</a> diet, invented by English undertaker William Banting in 1863, who had used the diet to help him lose weight when he was obese. The diet appeared in many health manuals and women’s magazines, recommending people follow a <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.1550-8528.1993.tb00605.x">high protein, low carbohydrate plan</a> that avoided pork, beer, potatoes, and bread.</p>
<p>The Banting diet’s focus on avoiding carbohydrates set the trend for other popular diets at the time. For example, the dry-diet instructed users consume only one pint of fluid per day, no soups, sauces, or alcohol, and to avoid pastry, puddings, white bread, potatoes, and sugar. Another diet plan published in Home Science Magazine in 1905 told readers to avoid carbs, excess fluids, desserts, and to walk four miles a day.</p>
<p>Until the 1920s, weight loss <a href="https://journals.sagepub.com/doi/abs/10.1177/1357034X07074780">was not</a> an exclusively female domain. But by the interwar period (the 1920s and 30s), medical concerns over body weight were equalled by popular notions of beauty that called for slimness, which saw many diets being marketed exclusively at women.</p>
<p>The emergence of the 1920s feminine ideal of the “New Woman”, with her slim, androgynous outline, coupled with women’s increased spending power, may have also driven the popularity of diets during this era. As detailed by the magazine Woman’s Outlook, the “anti-fat reducing craze” was widespread in Britain by 1926. Home weighing scales had also become common, allowing people to easily monitor their weight. All this resulted in an abundance of diet plans and books, such as the Hay diet (invented by physician William Hay), which advocated avoiding certain food combinations to maintain the body’s balance, and “Slimming for the Million” by Eustace Chesser, which eliminated carbohydrates.</p>
<p>Avoiding carbs remained at the centre of most popular diets in interwar Britain. But some diets – such as the salad days or fast days diets – placed focus on limiting calories. For example, the 18-day diet, published in 1929 by the Daily Mail, suggested people avoid carbs and follow a strict diet. Readers were told to only eat half a grapefruit, one egg, one slice of Melba toast, six slices of cucumber, and tea or coffee for lunch. For dinner, they were limited to two eggs, one tomato, half a head of lettuce, and half a grapefruit. </p>
<h2>The 1950s and 60s</h2>
<p>While slimming diets unsurprisingly played next to no role during wartime and rationing, the years that followed witnessed an explosion of commercial weight loss solutions – all in the name of <a href="https://muse.jhu.edu/book/13172">cultivating a slim, beautiful body</a>.</p>
<p>By the late 1950s and early 1960s, body cultivation through dieting had firmly become a woman’s domain and dieters could choose from a plethora of regimens to reduce body weight – which had increased on average as a result of the <a href="https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC2550498&blobtype=pdf">postwar consumer boom</a>. As before, low-carbohydrate approaches dominated – including the crash diet, the third-day diet, and the <a href="https://www.researchgate.net/profile/Avner_Offer/publication/9068233_Body_Weight_and_Self-Control_in_the_United_States_and_Britain_since_the_1950s/links/540d71af0cf2df04e7549d02/Body-Weight-and-Self-Control-in-the-United-States-and-Britain-since-the-1950s.pdf">daffodil diet</a>, which claimed would “give you the slim trim figure of a Spring Daffodil”.</p>
<figure class="align-center ">
<img alt="1950s woman showing off her fridge." src="https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/377779/original/file-20210108-19-tj2vul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In the 1950s, focus turned to portion sizes and low calorie diets.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-open-refrigerator-99385886">Everett Collection/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Towards the end of the 1960s, weight loss regimens began focusing on limiting portion sizes and consuming as few calories as possible. The three-day-liquid diet from 1968, published in Woman’s Own, suggested readers only consume two eggs, two pints of fresh milk, juice from two big oranges, and one dessert spoonful of olive oil, as well as as much lemon tea or coffee as they wanted (no sugar). This was to help followers “forget sweetness”. </p>
<p>The emergence of slimming clubs, commercialised weight loss solutions, and fad diets during this period was partly driven by a recognition of the <a href="https://www.gla.ac.uk/media/Media_228377_smxx.pdf">links between obesity and ill-health</a>. But it’s also partly the result of culturally constructed beauty ideals for women that were linked to <a href="https://www.goodreads.com/book/show/468872.Fat_Is_a_Feminist_Issue">lower body weight</a>. </p>
<h2>The 70s and 80s</h2>
<p>Popular weight loss regimes became more than just slimming diets, and, in women’s magazines such as Woman’s Own, were increasingly touted as self-help tools for the emancipated woman. Achieving success and inner balance required control of the body through dieting and, increasingly, exercise.</p>
<p>The links between fitness and health resulted in the widespread emergence of fitness studios with popular exercise classes such as aerobics – a term first coined by Kenneth Cooper in 1960s, <a href="https://core.ac.uk/download/pdf/189015205.pdf">recommending gym workouts and high-energy movement</a>. Regimes in the 1980s emphasised low-fat foods, which resulted from the introduction of <a href="https://openheart.bmj.com/content/2/1/e000196.abstract?sid=7217c2a8-513e-4e7e-837a-fe5389053fde">dietary guidelines</a> aimed at reducing fat intake in the late 70s and 80s. </p>
<p>The F plan diet was one of the most popular in this era, emphasising eating high fibre and low calories – and advised that people eat foods like muesli for breakfast, salad with pulses for lunch, and lean meats for dinner. At the end of the 20th century, diets such as <a href="https://www.pure.ed.ac.uk/ws/files/18605834/_We_can_t_go_back_a_hundred_million_years_.pdf">Atkins or the south beach diet</a> returned to Banting’s emphasis on cutting carbs for weight loss. </p>
<p>Despite the knowledge we now have about losing weight through dieting, fad diets continue to be popular. Modern diets such as keto or paleo even share many similarities with the low-carb, calorie restrictive diets popular throughout the 20th-century. Yet research shows fad diets may actually lead to <a href="https://pdfs.semanticscholar.org/d420/46557810136fa0764363353cca9efcd10b59.pdf">weight gain and disordered eating</a>. </p>
<p>So while the appeal of fad diets is understandable, evidence shows a balanced diet and exercising more are the best ways to lose weight.</p><img src="https://counter.theconversation.com/content/151731/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Myriam Wilks-Heeg 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>20th-century fad diets didn’t look all that different from those popular today.Myriam Wilks-Heeg, Lecturer in Twentieth Century History, University of LiverpoolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/763032017-06-21T20:02:00Z2017-06-21T20:02:00ZFeeling euphoric on a low-carb diet? The effect on your brain is similar to an illicit drug<figure><img src="https://images.theconversation.com/files/174868/original/file-20170621-8977-mfwsk1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A very low-carb diet can prompt changes in your brain similar to that caused by the illicit drug GHB.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/387499906?src=n7Jb-vNzt4zt5Cdcn5AsCA-1-0&size=medium_jpg">from www.shutterstock.com</a></span></figcaption></figure><p>Some people on very low-carb diets say they feel <a href="https://www.paleohacks.com/ketosis/does-ketosis-and-or-intermittent-fasting-cause-euphoria-35565">euphoric</a>, <a href="http://lowcarbediem.com/have-more-energy-sleep-less-and-get-more-done">have clear minds</a> and lose their appetite.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"455930671148453889"}"></div></p>
<p>Going low-carb might even mimic the effects of <a href="https://theconversation.com/weekly-dose-ghb-a-party-drug-thats-easy-to-overdose-on-but-was-once-used-in-childbirth-73266">GHB</a> – the recreational drug better known as fantasy, liquid ecstasy or grievous bodily harm – on the brain.</p>
<p>To understand why we need to look at how the body processes a very low-carb diet, one that typically limits carbohydrates to no more than <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2359752/pdf/1743-7075-5-9.pdf">50 grams a day</a>. That’s one cup of rice, two slices of bread or roughly 10% of your total daily energy needs.</p>
<h2>Your body thinks it’s starving</h2>
<p>A very low-carb diet flips your metabolic switch from burning more carbs than fat, to more fat than carbs. This usually takes a few days in a process known as ketosis.</p>
<p>During this time, your body thinks it’s starving. Once it uses up most of your glucose (carb) reserves, the body stimulates the breakdown of stored fat into fatty acids and releases them into the blood.</p>
<p>When fatty acids reach the liver they’re converted into acetoacetate, an excellent metabolic fuel that belongs to a family of chemicals called ketones. That’s why very low-carb diets are sometimes called “ketogenic” diets.</p>
<p>Acetoacetate decomposes to carbon dioxide and acetone, the smelly solvent best known for its ability to remove nail polish. This is why very low-carb dieters and people who are fasting often have sweet smelling breath. </p>
<p>A healthy liver minimises the acetone lost via the lungs by converting most of the acetoacetate it produces to a more stable substance, called beta-hydroxybutyrate or BHB. And this is where those euphoric feelings could come from.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/4fw9E32bhoc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The molecule BHB, which your body produces during a very low-carb diet, is very similar to GHB, the recreational drug with psychoactive effects.</span></figcaption>
</figure>
<p><a href="https://www.ncbi.nlm.nih.gov/pubmed/17011713">BHB is almost identical to GHB</a>, the naturally occurring neurotransmitter, called gamma-hydroxybutyrate, that in synthetic form is used as a <a href="https://theconversation.com/weekly-dose-ghb-a-party-drug-thats-easy-to-overdose-on-but-was-once-used-in-childbirth-73266">recreational drug</a>.</p>
<p>BHB and GHB have exactly the same chemical formula. Both consist of just 15 atoms, with the only difference being the position of one hydrogen and oxygen atom. It’s not too surprising, therefore, the two molecules share the <a href="https://www.ncbi.nlm.nih.gov/pubmed/15173314?dopt=Abstract">same carrier</a> across the <a href="https://theconversation.com/explainer-what-is-the-blood-brain-barrier-and-how-can-we-overcome-it-75454">blood-brain-barrier</a>, the impermeable tissue that protects the brain. </p>
<p>During ketosis, BHB can reach high levels <a href="http://journals.sagepub.com/doi/pdf/10.1097/00004647-200010000-00012">in the brain</a>, where it can bind to the same anxiety-reducing <a href="https://www.karger.com/Article/FullText/443173">receptors as GHB</a>. They bind with <a href="https://www.ncbi.nlm.nih.gov/pubmed/7070203">sufficient affinity</a> that they may have <a href="https://www.ncbi.nlm.nih.gov/pubmed/17011713">similar effects</a>.</p>
<p>There are no reports of <a href="https://www.ncbi.nlm.nih.gov/pubmed/26893218">BHB supplements</a> or low-carb diets causing any of GHB’s adverse effects, like loss of consciousness, seizures and death.</p>
<p>So, apart from the similar-sounding name, what evidence is there that BHB produced by the liver by people on a very low-carb diet has euphoric, GHB-like effects in the brain?</p>
<h2>Fasting for the original ‘natural high’</h2>
<p>The first case of euphoria directly attributed to ketosis was reported by Walter Bloom, who pioneered therapeutic fasts for obesity <a href="https://www.ncbi.nlm.nih.gov/pubmed/13656492?dopt=Abstract">in the 1950s</a>. After several days without food, his patients lost their appetite, felt remarkably well, and experienced a mild intoxication:</p>
<blockquote>
<p>not dissimilar to the effects of ethanol.</p>
</blockquote>
<p>Bloom speculated that acetoacetate had caused the inexplicable jubilation.</p>
<p>Other people have observed similar effects, including three Scottish doctors whose patients fasted for <a href="http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(66)92925-4/abstract">up to 249 days</a> in the 1960s. After several days without food, their appetites subsided and all patients felt an increased sense of well-being which:</p>
<blockquote>
<p>in some amounted to frank euphoria.</p>
</blockquote>
<p>Unfortunately, no studies of the euphoria reported by low-carb dieters have been conducted, as far as we know.</p>
<p>So, researchers don’t know the exact cause of these feelings. Acetoacetate, acetone and BHB, or any of their metabolites, may all be involved, as well as the effects of low blood sugar, which can cause <a href="https://www.diabetesselfmanagement.com/managing-diabetes/blood-glucose-management/understanding-hypoglycemia/">euphoria and giddiness</a>.</p>
<p>A good place to start might be to image brain activity in people on a very low-carb diet and compare activity with people on a normal, non-calorie restricted diet. The aim would be to see if brain imaging of people on a very low-carb diet has similar effects on brain activity seen when <a href="https://www.nature.com/npp/journal/vaop/naam/abs/npp2017110a.html">people take GHB</a>.</p>
<p>And if you’re thinking of going on a very low-carb diet to get that high, beware. Side effects include <a href="https://www.ncbi.nlm.nih.gov/pubmed/19064531">loss of calcium from bones</a>, increased risk of <a href="https://www.ncbi.nlm.nih.gov/pubmed/19596731">kidney stones</a> and <a href="http://onlinelibrary.wiley.com/doi/10.1111/dmcn.12462/full">growth retardation</a>.</p>
<hr>
<p><em>Special thanks to PhD candidate Ruben Meerman for his input, including his animation of BHB versus GHB.</em></p><img src="https://counter.theconversation.com/content/76303/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Brown 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>Some people on very low-carb diets say they feel euphoric, have clear minds and lose their appetite. Here’s why.Andrew Brown, Professor and Head, School of Biotechnology and Biomolecular Sciences, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/458232015-08-13T20:30:36Z2015-08-13T20:30:36ZEat food, not nutrients: why healthy diets need a broad approach<figure><img src="https://images.theconversation.com/files/91723/original/image-20150813-21401-1ix0h71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">We need to stop fussing over macronutrients and think about foods.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/eugenia_loli/17459500360/">Eugenia Loli/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>There seems to be a shortening gap between studies about diet, nutrition and health. And each starts another conversation about trans vs saturated vs polyunsaturated fats, or this diet vs that, or, as is today’s case, fats vs carbohydrates.</p>
<p>In a paper published today in the <a href="http://www.cell.com/cell-metabolism/abstract/S1550-4131(15)00350-2">journal Cell Metabolism</a>, researchers found that when 30% of a day’s kilojoules were restricted by cutting fats (diets with a higher intake of carbohydrates), participants in their study lost more body fat compared to when the same amount of energy was restricted by cutting carbs (diets with a higher intake of fat).</p>
<p>This study used a type of meticulous metabolic research, which is expensive and unsuited to lengthy periods, but valuable for exploring the physiology of reducing equal dietary contributions from fat or carbohydrate. But like much dietary analysis, it may be shining a light on the wrong issues altogether.</p>
<h2>The good, the bad and the ugly</h2>
<p>The most important aspect of any diet is that it should be practical and healthy enough to follow for the rest of your life. There’s no magic bullet for weight loss. While some people claim they find it easier to cut out foods high in carbohydrates, others find it easier to avoid high-fat foods. </p>
<p>If you need to lose weight, <a href="http://jama.jamanetwork.com/article.aspx?articleid=1900510">cutting down is what helps</a>. But few people can stick to any extreme diet for life, so what you substitute is just as important as what you cut out – especially for long-term health.</p>
<p>Choices based only on macronutrients (foods required in large amounts in the diet, such as fats, carbohydrates and protein) miss important aspects of many foods and open the diet to imbalance. Carbohydrate foods, for instance, include nutritionally worthy choices – such as legumes, wholegrains, fruits, milk and yoghurt – but also a huge range of items high in sugar or refined starches with little or no nutritional attributes. “Cutting carbs” doesn’t distinguish between the good and bad foods in this category.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91726/original/image-20150813-21387-vtzp7i.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">This may not be the best way to get your daily ration of fruit.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/chodhound/7755540602/">Adrian Scottow/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The same thing happens with fats. Sources of unsaturated fat – such as nuts, seeds, avocado or extra virgin olive oil – have proven health benefits. But there’s no evidence for any benefits of lard, dripping, cream, fast foods or any of the fatty snack foods that account for much of our saturated fat intake. And no long-term study shows sustained weight loss or other health benefits from a diet high in saturated fats.</p>
<p>Some foods are more even problematic. Most fast foods are high in saturated fat and salt, and lack dietary fibre. And they’re not only largely devoid of vegetables (apart from the odd gherkin), but often displace meals that would have contained vegetables. </p>
<p>Biscuits, cakes, pastries, many desserts and confectionery provide a double whammy with high levels of unhealthy fats as well as sugar and refined starches. Make that a triple whammy because most lack any nutritional virtue as well.</p>
<h2>From bad to worse</h2>
<p>Assumptions based on macronutrients are simply too gross to be meaningful. This is apparent in so-called meta-analyses based on a mixture of cohort and case-control studies that use different methods and time frames relating to what people eat, and fail to report all aspects of the diet.</p>
<p><a href="http://www.ncbi.nlm.nih.gov/pubmed/24723079">One review</a>, for instance, claimed that saturated fat was unrelated to cardiovascular disease. But it ignored the adverse impacts of the foods that had replaced saturated fats and provided no information about the foods that provided saturated fat in the first instance. </p>
<p>Worse still, such analyses are prone to many errors. A long <a href="https://www.mja.com.au/journal/2015/202/8/sceptics-undermine-effective-dietary-and-heart-health-advice?utm_source=MJA+news+alerts&utm_campaign=2313abfd38-MJA_news_vol_202_Issue_8_4_May_20155_1_2015&utm_medium=email&utm_term=0_8c7e70a099-2313abfd38-31315341">check of every reference</a> used in that meta-analysis showed that the conclusion would have differed if 25 studies had either not been omitted or had been reported correctly (sadly, it’s paywalled). </p>
<p><a href="http://www.bmj.com/content/351/bmj.h3978">Another recent review</a> also failed to show any clear association between higher saturated fat intake and all-cause mortality, heart disease, ischaemic stroke or type 2 diabetes, although the authors were unable to confidently rule out increased risk for heart disease deaths. They also noted that the certainty of associations between saturated fat and all outcomes was “very low”, which means we don’t yet understand the association between saturated fats and disease.</p>
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<img alt="" src="https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=479&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=479&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=479&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=602&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=602&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91725/original/image-20150813-21387-123i532.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=602&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Not all dairy products are created equal.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/samir-rahamtalla/393729330/">Samir Rahamtalla/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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<p>Hopefully, further research will distinguish between food sources of saturated fats; they are not all equal. There’s already good evidence that processed meats can have more deleterious effects than fresh meat. And that fermented dairy products, such as <a href="http://ajcn.nutrition.org/content/71/3/674.full.pdf+html">yoghurt</a> and <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383488/">cheese</a>, may also have health benefits and are distinctly different for heart health risk <a href="http://ajcn.nutrition.org/content/94/6/1479.long">compared to butter</a>.</p>
<p>Swapping saturated fat for sugar or refined starches is worse than useless <a href="http://www.ncbi.nlm.nih.gov/pubmed/26185980">for preventing cardiovascular disease</a>. But please direct criticism of foods where fat has been replaced by sugar at the food industry. Dietary guidelines have always recommended limiting sugar as well as saturated fat. </p>
<h2>A sorry state of affairs</h2>
<p>Unfortunately, in most developed countries, sugar consumption remains high while intakes of vegetables, legumes, fruits, nuts and wholegrains are low. And while macronutrient intakes in countries such as Australia may look fine (31% of energy from fat and 44% from carbs), problems remain with the kinds and amounts of foods we consume.</p>
<p>Junk food and drinks were once consumed only as an occasional treat, but they now contribute significant portions of both adult and children’s diets – in Australia, 35% of adults’ and 41% of childrens’ energy intake. Confectionery and starchy, fatty, savoury snack food intake have also increased significantly. </p>
<p>It really is time to focus on foods instead of wasting time on macronutrients. <a href="http://www.eatforhealth.gov.au">Australia’s Dietary Guidelines</a> have made this change, as has the <a href="http://www.livsmedelsverket.se/globalassets/english/food-habits-health-environment/dietary-guidelines/kostrad-eng.pdf?id=8140">new simple Swedish equivalent</a>, which emphasises sustainable choices. <a href="http://www.fao.org/nutrition/education/food-based-dietary-guidelines/regions/countries/norway/en/">Norway</a> and <a href="http://www.fao.org/nutrition/education/food-dietary-guidelines/regions/europe/en/">20 European countries</a> also take a food focus and the number one point in <a href="http://189.28.128.100/dab/docs/portaldab/publicacoes/guia_alimentar_populacao_ingles.pdf">Brazil’s enlightened guidelines</a> is that diet is more than the intake of nutrients.</p>
<p>Consider the dozens of studies on Mediterranean diets, including randomised trials, where the fat and carbohydrate content vary but the health value depends on particular foods: extra virgin olive oil, nuts, vegetables, fruits, grains and legumes and a low intake of highly processed products. The take-home message from these is that we need to stop fussing over macronutrients and think about foods.</p><img src="https://counter.theconversation.com/content/45823/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rosemary Stanton 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>By focusing on micro- or macronutrients, most nutrition research fails to recognise the most important truth about food: diet is more than the intake of nutrients.Rosemary Stanton, Nutritionist & Visiting Fellow, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/226032014-01-31T00:06:34Z2014-01-31T00:06:34ZTV twins pitch sugar against fat but the combination is a killer<figure><img src="https://images.theconversation.com/files/40199/original/m73mz9mq-1391080568.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C2000%2C1332&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Yummy.</span> <span class="attribution"><span class="source">BBC/Joanna Barwick</span></span></figcaption></figure><p>This could have been such a yawn. Is sugar the “toxic drug” or fat “the deadly ingredient”? Is it yet more popularised quasi-science, claiming life-threatening consequences from foods we eat every day?</p>
<p>But <a href="http://www.bbc.co.uk/programmes/b03t8r4h">Sugar v Fat</a>, a BBC Horizon programme that took two identical twin doctors and put them on extreme low-fat and low-sugar diets for a month, was certainly different – possibly even a first for a diet programme. It was quick-moving, highly entertaining, and its conclusions were largely (but not completely) correct.</p>
<p>The big problem with attempts to show science on human subjects on television is that for science to show anything beyond the blindingly obvious or totally banal normally requires studies of large numbers of individuals. People can be enormously different, so we often need huge numbers to be sure that a result is true and a treatment or diet really does work. That’s even before we begin to consider statistics. </p>
<p>So choosing <a href="http://www.twinsuk.ac.uk/">a pair of</a> identical twins – Xand and Chris Van Tulleken – to compare the effects of low-carb and low-fat diets was inspired, because they are a genetic and metabolic match. And following two prevailing threads of dietary advice in the US and the UK, Xand took on a low-carb diet while Chris got low-fat.</p>
<p>Following any kind of rigid dietary advice for a month is very tough, which is why good dietitians don’t tend to give out inflexible dietary prescriptions, but the twins really got stuck in. As participants they were pretty average, just a little overweight perhaps, but nothing serious. Their body fat contents, estimated by the slightly erratic “BodPod” whole-body plethysmograph (which measured changes in body volume) were 22% and 26%, which is a bit high for men. </p>
<h2>Mental agility</h2>
<p>From early on, it was apparent that Chris was enjoying his low-fat diet, with its reciprocal high carbohydrate content and the energy it gave him. But while Xand started by enjoying the Atkins-style meats, cheeses, creams and other high-fat foods, he was soon missing his carbs. He felt sleepy and lacked energy. His restricted carbohydrate supply limited glucose supply to his brain and he fared much less well in a test of mental agility and memory, playing the New York Stock Exchange on-screen. </p>
<p>So round one was a convincing victory for the low-fat/high-carb UK-style diet (Chis made pots of money on the stock exchange, while Xand lost track and struggled badly). This shouldn’t be a surprise to anyone with knowledge of nutrition: the brain functions <a href="http://www.ncbi.nlm.nih.gov/books/NBK22436/">almost exclusively</a> on glucose as its fuel. </p>
<h2>Physical performance</h2>
<p>Similarly, when it came to physical performance, a fortnight into the diets, Xand soon flagged in a cycling trial up a hill (even with a Tour de France trainer) while Chris stormed on to the top. The high-carb/low-fat UK-style diet gave Chris tremendous energy. Any athlete or exercise-lover knows this: high intensity exertion and untrained muscles need glucose. This can only really come from dietary carbohydrate. </p>
<p>The full story is a little more complicated than it was possible to show in the programme, as muscles can be trained to burn fat for endurance activity. But even Tour de France cyclists, we learned, eat huge amounts of the ultimate energy food – porridge. It releases energy more slowly and consistently. So round two also went convincingly to the low-fat/high-carb UK-style diet.</p>
<h2>Metabolism</h2>
<p>Round three was the denouement, the metabolic round, with a series of physiological tests at the beginning and the end of the month. </p>
<p>The backdrop to this was an interview with the ubiquitous Professor Robert Lustig, the latest in a very long series of high-profile individuals who have attacked sugar as the root of all health-evils. He recently generated publicity from <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0057873">a European survey</a> which purported to show that consuming more sugary drinks caused diabetes. This old chestnut has been debated for years. But Lustig’s study, like many before, failed to measure body fat, which is the true culprit. It was pointed out on the programme that there was no clear published evidence that sugar has any uniquely damaging role, and Diabetes UK recently <a href="http://www.diabetes.org.uk/Documents/About%20Us/What%20we%20say/Does%20sugar%20cause%20Type%202diabetes%20final%20oct%202013.pdf">released a paper</a> to that effect.</p>
<p>So how did the twins do in the metabolic round? A slightly clumsy eat-till-you-are-full laboratory experiment appeared to show that Chris would eat more calories from his low-fat/high-carb diet than Xand from his low-cab/high-fat diet. But this wasn’t a well-designed experiment. An alternative interpretation, not discussed, was that Chris simply enjoyed his high-carb foods more. A better design would be to have offered them both the same buffet selection to choose from. An important point was made though – fat gives you twice as many calories per mouthful as sugar.</p>
<p>There was no difference in their blood cholesterols, but worryingly Xand’s blood glucose had actually risen, not fallen, on the low-carb diet, and his insulin levels were paradoxically high. Essentially, he became “insulin-resistant” – the first step towards Type 2 diabetes. This is exactly the result experienced nutritional scientists would expect, even if someone doesn’t gain weight. High fat diets promote diabetes because insulin <a href="http://www.sciencedaily.com/releases/2012/05/120522114536.htm">stops working well</a>.</p>
<h2>The weigh-off</h2>
<p>The twins’ weight changes on their different diets were not as well explained. Chris remained within 1kg or so of his starting weight, despite eating as much high-carb food as he liked for a month, while Xand lost 3.5kg on th low carb diet. A rather complicated explanation was offered, based again on the BodPod measurements, to suggest that Xand had lost 2kg of muscle. That would be really worrying, but improbable. </p>
<p>The true explanation for his weight loss is much simpler: an extreme low-carb diet, as favoured by Lustig and <a href="http://www.bbc.co.uk/news/magazine-22145709">before him Atkins</a>, completely depletes the body of carbohydrate stores over a few days. Carbohydrate is stored in the liver and in muscle in the form of glycogen, where each gram of carbohydrate is stored with about 4g of water. On average, people have about 400g of glycogen stores, so its total weight is about 2kg. A tallish biggish man like Xand is likely to have nearer 3kg in total, and all that is lost rapidly on a low-carb diet. </p>
<p>Large studies comparing low-fat and low-carb diets, aminly in women, have consistently shown about 2kg greater weight loss, at least initially, with the low-carb diet. It has been known for 40 years that <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1748-1716.1970.tb04764.x/abstract;jsessionid=2D1A58B5779B612B367183D202CA454F.f01t02">this difference is water</a>. A good trick if your name is Atkins and you can persuade people to pay for it. I wish the Horizon programme had explained that.</p>
<p>The conclusion for metabolic risks and weight gain, shown nicely by some very persistent rats and a sad-looking cheesecake in Paul Kenny’s lab at Mount Sinai Hospital, is that the bogey man is not an overall high-fat diet, nor an overall high-sugar or high-carbohydrate diet. </p>
<p>The problem is our extraordinary weakness for foods which present us with a 50:50 mix of the two. That type of food does not exist in nature or in our evolutionary history. But it is sitting in a fridge in almost every American home as a grazing food. On both sides of the pond, the most popular doughnut is the plain, sugar-glazed type, which is almost exactly 50:50 fat:carbohydrate.</p>
<h2>Takeaway anyone?</h2>
<p>There is much more dietary tweaking if you seek perfection, for example the hazards from trans-fatty acids, now reduced by trade agreements but still not banned in UK so likely to creep back into our foods, and high intakes of fructose readily converted into liver fat. </p>
<p>This is one thing Lustig is right about: we can’t let <a href="https://theconversation.com/eu-fructose-ruling-means-dodgy-health-claims-are-easier-to-make-19495">fructose intakes in the UK</a> climb to reach the levels in US. And then there’s the small matter of some 27 essential nutrients needed in all human diets that is mostly ignored by manufacturers and caterers.</p>
<p>So it’s a simple take-home message then: avoid manufactured foods which present carbohydrate and fat in equal proportions, and if you want to stay awake, active and smart, go for a UK-style higher carbohydrate, lower fat diet. Well done, Horizon! Two stars and a wish!</p><img src="https://counter.theconversation.com/content/22603/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Lean is Chief Scientific Officer for Eat Balanced, a ready-meals company.</span></em></p>This could have been such a yawn. Is sugar the “toxic drug” or fat “the deadly ingredient”? Is it yet more popularised quasi-science, claiming life-threatening consequences from foods we eat every day…Mike Lean, Chair of Human Nutrition, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.