tag:theconversation.com,2011:/africa/topics/brown-fat-8864/articlesBrown fat – The Conversation2020-12-16T20:08:43Ztag:theconversation.com,2011:article/1519822020-12-16T20:08:43Z2020-12-16T20:08:43ZBaby mice ‘shut down’ to survive extreme cold on the highest mountain tops<figure><img src="https://images.theconversation.com/files/375179/original/file-20201215-21-1149vme.jpg?ixlib=rb-1.1.0&rect=26%2C8%2C5886%2C4042&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">North American deer mice pups have adapted to extreme cold conditions in an unusual way.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>It’s early 2019, and biologist Jay Storz is struggling to breathe. He has just made it to the top of Llullaillaco, a Chilean volcano about three-quarters the height of Mount Everest, in search of a rumour. </p>
<p>Up this high, the air is thin, so there isn’t much oxygen and every step is an effort. Storz’s colleague, Mario Perez Mamani, spots movement among the rocks and Storz springs into action. He makes a successful grab and sits back, smiling. In his fist is the highest-dwelling animal in the world: <a href="https://doi.org/10.1073/pnas.2005265117">A yellow-rumped leaf-eared mouse (<em>Phyllotis xanthopygus rupestris</em>)</a>.</p>
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<figcaption><span class="caption">Biologists Jay Storz and Mario Perez Mamani capture a yellow-rumped leaf-eared mouse.</span></figcaption>
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<p>I’m a Canadian biologist who is part of an international team of scientists that includes Storz; we study mountain top mice to learn how animals adapt to extreme environments. When it comes to living the high life, small rodents and lagomorphs (relatives of rabbits) are the undisputed high-altitude champions from the Andes to the Himalayas. Our study species, the North American deer mouse (<em>Peromyscus maniculatus</em>), is found from sea level to the summit of the highest Rocky Mountains, giving it the broadest altitudinal range of any mammal on the continent.</p>
<h2>Surviving extreme environments as a pup</h2>
<p>Mountain tops are some of the most extreme environments on Earth, and many summits are freezing cold all year round. For small mice, this can be a big problem. Their surface area is large relative to their mass, so they lose heat quickly.</p>
<p>Most warm-blooded animals like birds and mammals — endotherms — use energy from food to make their own heat and prevent their body temperature from dropping too low. Mammals use muscle to shiver or a special kind of fat called brown adipose tissue that makes heat without shivering. Both shivering muscle and brown fat need energy and oxygen to make heat. </p>
<p>Oxygen is in short supply on a mountain top but high-altitude mice have found a way around this problem. Highland populations of the North American deer mouse, native to the Rocky Mountains and the White Mountains, have evolved to maximize heat production. Their <a href="https://doi.org/10.1073/pnas.1120523109">brown fat and skeletal muscle</a> are fat-burning machines, and their specialized <a href="https://doi.org/10.1098/rspb.2019.2750">cardiovascular and respiratory systems</a> deliver all the oxygen and fuel needed. Maximizing heat production means an adult mouse is more likely to <a href="https://doi.org/10.2307/2640830">survive on the cold mountain top</a>.</p>
<h2>Generating heat for survival</h2>
<p>Some mammals are born with fully functioning heat-generating mechanisms. But for many species, these systems mature after birth. In these animals — including humans and mice — brown fat matures first and takes on early heat production. </p>
<p>At sea level, a baby mouse’s brown fat takes about <a href="https://doi.org/10.1098/rspb.2019.0841">eight days to develop</a>. By that point, the babies, or pups, have tripled in size and are starting to grow fur. In another two short weeks, they will be old enough to leave home, but these first few weeks are treacherous. High predation risk and the energetic costs of growth mean less than half of baby mice born in the wild make it to adulthood. </p>
<p>But high-altitude mice have evolved a surprising strategy to help survive this early life stage: they let themselves get cold. Our research found that <a href="http://doi.org/10.1242/jeb.210963">heat-producing systems of high-altitude deer mouse pups mature slowly compared to mice from lower elevations</a>. When we looked at the genes responsible for these traits, we found that in both brown fat and skeletal muscle, <a href="https://doi.org/10.1093/molbev/msaa086">the metabolic pathways associated with heat production were turned off in high-altitude pups</a>, who had to rely on their mothers for warmth.</p>
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<a href="https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hand holding a very young mouse." src="https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/374537/original/file-20201211-17-1h74p7w.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A 10-day-old North American deer mouse pup. At this age, a lowland pup is able to stay warm using specialized heat-producing brown fat. Pups native to high altitudes have evolved to delay the maturation of this tissue.</span>
<span class="attribution"><span class="source">(Cayleih Robertson)</span>, <span class="license">Author provided</span></span>
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<p>Mother rodents will sit on their pups while they nurse, keeping them nice and toasty. If pups can’t produce their own heat, their body temperature will slowly drop whenever the mother is away.</p>
<h2>Tolerance for cold</h2>
<p>Humans get hypothermia if our body drops by 2 C, so this may seem dangerous. But baby mice are remarkably cold-tolerant. Their body temperature can drop almost to freezing for hours, warming up again when their mother returns.</p>
<p>Our research leads us to believe that high-altitude mice conserve their energy use for growing, rather than staying warm. The combination of cold and low oxygen means that most mammalian babies (from humans to rats) can’t grow properly at high altitude.</p>
<p>The deer mouse is able to survive to adulthood at high altitudes because of its ability to slow down metabolic activity and conserve energy. Since this is the exact opposite strategy used by adult deer mice, our work highlights how important it is to study young animals if we want to understand how a species has evolved.</p><img src="https://counter.theconversation.com/content/151982/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cayleih E. Robertson receives funding from the Natural Sciences and Engineering Research Council of Canada</span></em></p>Mice pups living on mountain tops reserve their energy for growth rather than warmth. When they get too cold, they conserve energy by slowing down their metabolic processes.Cayleih E. Robertson, Postdoctoral Fellow in Comparative Physiology, McCall MacBain Teaching and Leadership Fellow, McMaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1381412020-05-18T09:22:30Z2020-05-18T09:22:30ZBrown, white and beige: understanding your body’s different fat cells could help with weight loss<figure><img src="https://images.theconversation.com/files/335343/original/file-20200515-138610-1gwfk56.jpg?ixlib=rb-1.1.0&rect=35%2C8%2C5955%2C4104&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">White fat cells are usually found beneath the skin and in the abdominal cavity.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/fat-cells-inside-human-organism-3d-396411568">Pavel Chagochkin/ Shutterstock</a></span></figcaption></figure><p>We know that carrying excess fat is bad for us and can contribute to a number of diseases, such as diabetes. But not all fat is created equal. </p>
<p>While certain types of fat cells can accumulate in our bodies and cause health problems, other types have evolved to turn fuel into heat – so they can actually burn calories. Recent research even shows that having <a href="https://academic.oup.com/jcem/advance-article-abstract/doi/10.1210/clinem/dgaa183/5825408?redirectedFrom=fulltext">higher concentrations of “good” fat cells</a> in our bodies can help us burn more calories when we’re exposed to cold temperatures.</p>
<p>This idea of different “coloured” fats – brown, white and beige – often comes up in <a href="https://www.womansworld.com/posts/diets/brown-fat-128932">fad diets</a> encouraging you to eat special foods for weight loss without much proof they work. But understanding the science behind these different types of fat cells – and how to transform one type into another – really could be an important way to keep healthy, and even treat serious conditions such as obesity. </p>
<h2>White, brown, and beige cells</h2>
<p>There are two main types of fat cells.</p>
<p>White fat cells are found in they body’s <a href="https://www.britannica.com/science/connective-tissue">connective tissues</a>, usually beneath the skin (subcutaneous fat) and in the abdominal cavity (visceral fat). </p>
<p>When we eat food, the white fat cells primarily convert excess energy in the form of glucose that it doesn’t need into <a href="https://www.nature.com/articles/s41580-018-0085-z">lipid droplets</a>, usually as molecules called <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/triacylglycerol">triglycerides</a>. These produce signalling molecules that <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/homeostasis">regulate appetite and energy balance</a>.</p>
<p>Brown fat cells, on the other hand, were traditionally believed to be found only in newborn babies and would disappear in infancy. Later, research showed that brown fat cells exist in the body <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5206678/">throughout your life</a>.</p>
<p>Brown fat cells are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3661606/">located in regions</a> between the shoulder blades, neck, along the spinal cord, and above the collarbone. But they can emerge in other parts of the body such as <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3661606/">around the vital organs</a>, where they turn food into heat. </p>
<p>But research has found a <a href="https://www.ncbi.nlm.nih.gov/pubmed/23782940">third type of fat cells</a>, called beige or “brite” (brown in white) fat cells. These cells act like brown fat cells, but are found in similar areas as white fat cells.</p>
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<img alt="" src="https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335347/original/file-20200515-138654-1fg4rca.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">
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<span class="caption">The process of</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/travel-concept-freezing-tourist-woman-feeling-1085364536">Anetlanda/ Shutterstock</a></span>
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<p>Beige fat cells are derived from white fat in a process called “browning” which is triggered by exposure to low temperatures, typically 3°C above a <a href="https://www.nature.com/articles/s41598-019-49936-x">person’s shivering temperature point</a>, which is <a href="https://www.sciencedirect.com/science/article/pii/S0306456518301918">around 11°C for women and around 9°C for men</a>.</p>
<p>Other stimuli such as <a href="https://www.ncbi.nlm.nih.gov/pubmed/29102386">good nutrition</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0026049517303219">exercise</a> are also believed to encourage the browning process.</p>
<h2>What their appearance means</h2>
<p>White fat cells are typically round cells of variable sizes with a single, large, lipid droplet. These droplets can be converted to fatty acids during starvation or when energy demands increase. Fatty acids are the building blocks of fats which can be absorbed into the blood.</p>
<p>Brown fat cells are smaller, and have many small lipid droplets per cell. Brown fat cells also contain many energy generating organelles called mitochondria. These are rich in iron, which give them their brown colour when exposed to oxygen.</p>
<p>Beige fat cells have features midway between white and brown. They come from white parent cells, but function like brown fat cells by burning energy to produce heat when the core body temperature dips. The browning process is helped by <a href="https://www.nature.com/articles/s41598-019-49936-x">cold temperatures</a>, and the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4435534/">nervous</a> and <a href="https://stm.sciencemag.org/content/11/495/eaax9559">immune</a> systems.</p>
<h2>Changing fat type</h2>
<p>It’s long been known that white fat cells can acquire the characteristics of brown fat cells under certain conditions, such as <a href="https://link.springer.com/article/10.1007/s13105-018-0658-5">low temperatures and certain proteins</a>. But researchers now know that all types of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4663373/">fat cells can change</a> from one form to another depending on what triggers they’re exposed to and the demands placed on the organism they’re found in. </p>
<p>A fat cell can only change into another form one of two ways. It can switch its corresponding genes in a process known as <a href="https://www.researchgate.net/publication/10967311_Adipocyte_differentiation_and_transdifferentiation_Plasticity_of_the_adipose_organ">transdifferentiation</a>. Or, the change can be achieved by reverting any mature fat cells to their common parental form (dedifferentiation), then “reprogramming” their genes (<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3756103/">redifferentiation</a>). This second process can happen naturally, but is usually achieved in lab settings.</p>
<p>The conditions for natural change can also be sped up. Nutritional supplements, such as the flavonoids <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/oby.21706">resveratrol and quercetin</a>, which are found in fruits and vegetables, can help the browning process. <a href="https://www.ncbi.nlm.nih.gov/pubmed/29155135">Exercise</a> has also been shown to increase browning.</p>
<p>Exposure to temperatures slightly above the shivering point for at least two hours is also known to help with browning. However, this needs to be <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466122/">practised regularly</a> to see any real changes.</p>
<p>Studies also show that brown fat cells are associated with <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699856/">better health</a>. They encourage weight loss, which may subsequently reduce obesity and other related diseases caused by excess weight.</p>
<p>Brown fat cells also reduce the risk of <a href="https://www.cell.com/trends/endocrinology-metabolism/fulltext/S1043-2760(15)00046-6">hypothermia</a> and can reduce the risk of diabetes by increasing insulin sensitivity. The ability to cause the browning of white fat cells and turn them into beige cells therefore brings the potential for better health.</p><img src="https://counter.theconversation.com/content/138141/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Trust Diya 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>We all have white and brown fat cells – but recent research shows there’s a third type, called “beige” cells.Trust Diya, Lecturer in Biological Sciences, Staffordshire UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1197402019-07-04T19:47:27Z2019-07-04T19:47:27ZResearch Check: can drinking coffee help you lose weight?<figure><img src="https://images.theconversation.com/files/282584/original/file-20190704-126391-cjagi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As keen as we may be to hear about any health benefits of drinking coffee, the headlines aren't always what they seem.</span> <span class="attribution"><span class="source">Janko Ferlic/Unsplash</span></span></figcaption></figure><p>Researchers from the University of Nottingham in the UK recently published a study in the journal <a href="https://www.nature.com/articles/s41598-019-45540-1">Scientific Reports</a> suggesting caffeine increases brown fat. </p>
<p>This caught people’s attention because brown fat activity burns energy, which may help with weight loss. Headlines <a href="https://www.independent.co.uk/news/health/coffee-cup-weight-loss-study-research-brown-fat-a8973201.html">claimed</a> drinking coffee can help you lose weight, and that coffee is possibly even the “<a href="https://www.dailymail.co.uk/health/article-7174757/How-coffee-secret-fighting-obesity.html">secret to fighting obesity</a>”.</p>
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<p>Unfortunately, it’s a little more complicated than that. The researchers did find caffeine stimulated brown fat, but this was mainly in cells in a lab. </p>
<p>For a human to reap the benefits seen in the cells, we estimate they’d need to drink at least 100 cups of coffee.</p>
<p>Although part of this research did look at people, the methods used don’t support coffee or caffeine as weight-loss options. </p>
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<em>
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Read more:
<a href="https://theconversation.com/these-5-foods-are-claimed-to-improve-our-health-but-the-amount-wed-need-to-consume-to-benefit-is-a-lot-116730">These 5 foods are claimed to improve our health. But the amount we'd need to consume to benefit is... a lot</a>
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<h2>What is brown fat?</h2>
<p><a href="https://www.ncbi.nlm.nih.gov/pubmed/28707455">Brown adipose</a> (fat) tissue is found deep within the torso and neck. It contains fat cell types which differ from the “white” fat we find around our waistlines.</p>
<p>Brown fat cells adapt to our environment by increasing or decreasing the amount of energy they can burn when “activated”, to produce heat to warm us up. </p>
<p>When people are cold for days or weeks, their brown fat gets better at burning energy. </p>
<p>We understand caffeine may be able to indirectly accentuate and prolong some of these processes, mimicking the effects of cold exposure in stimulating brown fat.</p>
<p>Brown fat – and anything thought to increase its activity – has generated significant research interest, in the hope it might assist in the treatment of obesity.</p>
<h2>What did the researchers do in this latest study?</h2>
<p>The research team first conducted experiments where cells taken from mice were grown into fat cells in petri dishes. They added caffeine to some samples, but not others, to see whether the caffeinated cells acquired more brown fat attributes (we call this “browning”).</p>
<p>The dose of caffeine (one millimolar) was determined based on what would be the highest concentration that browned the cells but didn’t kill them. </p>
<p>The fat cell culture experiment showed adding caffeine did “brown” the cells. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/can-brown-fat-really-help-with-weight-loss-85987">Can 'brown fat' really help with weight loss?</a>
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<p>The researchers then recruited a group of nine people who drank a cup of instant coffee, or water as a control. </p>
<p>Before and after the participants drank coffee, the researchers measured their brown fat activity by assessing the temperature of the skin near the neck, under which a major region of brown fat is known to lie.</p>
<p>Skin temperature increased over the shoulder area after drinking coffee, whereas it didn’t after drinking only water.</p>
<h2>How should we interpret the results?</h2>
<p>Some people will criticise the low number of human participants (nine). We shouldn’t make broad recommendations on human behaviour or medicine based on small studies like this, but we can use them to identify new and interesting aspects of how our bodies work – and that’s what these researchers sought to do.</p>
<p>But whether the increased skin temperature after drinking coffee is significant cannot be determined for a few important reasons. </p>
<p>Firstly, although the study showed an increase in skin temperature after drinking coffee, the statistical analysis for the human experiment doesn’t include enough data to accurately compare the coffee and water groups, which prevents meaningful conclusions. That is, it doesn’t use appropriate methods we apply in science to decide if something really changed or only happened by chance.</p>
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<img alt="" src="https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=491&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=491&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282592/original/file-20190704-126400-2m1x3s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=491&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">Enjoy coffee for the taste, or the buzz. But don’t expect it to affect your waistline.</span>
<span class="attribution"><span class="source">From shutterstock.com</span></span>
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<p>Second, measuring skin temperature is not necessarily the most accurate indicator for brown fat in this context. Skin temperature has been validated as a way to measure brown fat after cold exposure, but not after taking drugs which mimic the effects of cold exposure – which caffeine is in the context of this study.</p>
<p>Myself and other researchers <a href="https://www.ncbi.nlm.nih.gov/pubmed/30203462">have shown</a> the effects of these “mimic” drugs result in diverse effects including increased blood flow to the skin. Where we don’t know if changes in the skin temperature are due to brown fat or unrelated factors, relying on this measure may be problematic. </p>
<p>Although also suffering its own limitations, PET (poistron emission tomography) imaging is currently our best option for directly measuring active brown fat.</p>
<h2>It’s the dose that matters most</h2>
<p>The instant coffee used in the study contained 65mg of caffeine, which is standard for a regular cup of instant coffee. Brewed coffees vary and might be double this. </p>
<p>Regardless, it’s difficult to imagine this dose could increase brown fat energy burning when studies using <a href="https://www.ncbi.nlm.nih.gov/pubmed/23064293">large doses</a> of more potent “cold-mimicking” drugs (such as ephedrine) cause no, or at best modest, increases in brown fat activity.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-can-caffeine-improve-your-exercise-performance-114087">Health check: can caffeine improve your exercise performance?</a>
</strong>
</em>
</p>
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<p>But let’s look at the caffeine dose used in the cell experiments. The one millimolar concentration of caffeine is a 20-fold larger dose than <a href="https://www.ncbi.nlm.nih.gov/pubmed/30747558">300-600mg of caffeine</a> dose used by elite athletes as a performance-boosting strategy. And this dose is five to ten times higher than the amount of caffeine you’d get from drinking an instant coffee.</p>
<p>Rough calculations therefore suggest we’d need to drink 100 or 200 cups of coffee to engage the “browning” effects of caffeine. </p>
<p>So people should continue to drink and enjoy their coffee. But current evidence suggests we shouldn’t start thinking about it as <a href="https://www.ncbi.nlm.nih.gov/pubmed/1318281">a weight loss tool</a>, nor that it has anything meaningful to do with brown fat in humans. <strong>– Andrew Carey</strong></p>
<hr>
<h2>Blind peer review</h2>
<p>This Research Check is a fair and balanced discussion of the study. The limitations identified by this Research Check apply equally to diabetes, which the study encompassed, but didn’t get picked up as much in the headlines. </p>
<p>Coffee contains more than caffeine, and while there is some evidence that modest coffee consumption may reduce diabetes risk, <a href="https://www.ncbi.nlm.nih.gov/pubmed/28675917">decaffeinated coffee seems to be as effective as caffeinated coffee</a>. This is consistent with the point made by the Research Check that you would need to drink an implausible number of cups of coffee to produce the effect seen with caffeine in the cultured fat cells. <strong>– Ian Musgrave</strong></p>
<hr>
<p><em>Research Checks interrogate newly published studies and how they’re reported in the media. The analysis is undertaken by one or more academics not involved with the study, and reviewed by another, to make sure it’s accurate.</em></p><img src="https://counter.theconversation.com/content/119740/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Carey has received funding from the National Health and Medical Research Council of Australia, Diabetes Australia Research Program, CASS Foundation, Clive and Vera Ramaciotti Foundation and the Helen Macpherson Smith Trust.</span></em></p><p class="fine-print"><em><span>Ian Musgrave has received funding from the National Health and Medical Research Council to study adverse reaction to herbal medicines and has previously been funded by the Australian Research Council to study potential natural product treatments for Alzheimer's disease. He has collaborated with SA water on studies of cyanobacterial toxins and their implication for drinking water quality.</span></em></p>Caffeine may be able to increase the function of what we call ‘brown fat’. But we shouldn’t immediately scramble for the closest long black or flat white and expect to see the kilos drop.Andrew Carey, Group Leader: Metabolic and Vascular Physiology, Baker Heart and Diabetes InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1062832018-11-27T14:16:00Z2018-11-27T14:16:00ZCould this be a solution for the obesity crisis?<figure><img src="https://images.theconversation.com/files/247258/original/file-20181126-140507-1rdi7hr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/187634345?src=iaoSivmZYXtcQUAGRirxMQ-2-17&size=medium_jpg">TAGSTOCK1/Shutterstock</a></span></figcaption></figure><p>Obesity is a disease where people accumulate more and more fat. When they reach a certain point, their fat stops working and they develop disease, such as type 2 diabetes. But not all fat is bad. The fat that accumulates in obesity is called white fat, but a second form of fat (brown fat) could actually be used to treat obesity. </p>
<p>Brown fat has evolved to turn fuel into heat. In small animals, like mice and voles, brown fat makes heat that helps them survive, even in freezing temperatures. </p>
<p>Brown fat can burn a stupendous amount of energy. When fully activated, just 100g of brown fat can burn 3,400 calories a day – nearly double most people’s daily food intake and more than enough to rapidly combat obesity. Even better, for reasons we don’t yet understand, when brown fat burns fuel, the body doesn’t sense it, meaning the person doesn’t eat more food to stay at the same weight. </p>
<p>While babies have a lot of brown fat, most adults have very little and, worse still, it is almost always inactive. However, <a href="http://diabetes.diabetesjournals.org/content/65/5/1179.long">recent studies</a> have shown we can develop more brown fat, making it an attractive approach to treat obesity. </p>
<h2>How to make more brown fat</h2>
<p>Unfortunately, the only reliable way to both increase the amount and activity of brown fat is to mimic a harsh winter – one without central heating and warm clothes. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247266/original/file-20181126-140507-1lwjeag.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A reliable but unpleasant way to increase brown fat.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/1020235939?src=_elJYp2zPGuhzbeCVROEjw-1-1&size=medium_jpg">Petrushin Evgeny/Shutterstock</a></span>
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<p>Placing people in the cold tells their body they need more heat and <a href="https://www.physiology.org/doi/full/10.1152/physrev.00015.2003">their nervous system tells brown fat to both turn on and become larger</a>. But putting people in a cold room for days is impractical, not to mention really unpleasant. </p>
<p>One option is to mimic the nervous signals that turn on brown fat using drugs. But the drugs that turn on brown fat also <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4298351/">increase blood pressure and heart rate</a>. This has the side effect of causing heart attacks, particularly in obese people, whom brown fat is supposed to treat. </p>
<p>The final problem with activating brown fat is that even if we could make every white fat cell in the body brown, it would not necessarily help. Brown fat needs an excellent blood supply to provide all those calories it can burn. It also needs nerves to contact the brown fat cells to switch them on.</p>
<h2>BMP8b: a potentially game-changing molecule</h2>
<p>A few years ago, we <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3383997/">identified</a> a molecule in mice called BMP8b. BMP8b is found at much higher levels in brown fat than in white fat, and the amount of it increased when we put mice in the cold. </p>
<p>Importantly, humans also have BMP8b. We discovered that deleting BMP8b in mice prevented brown fat from functioning. Because BMP8b is found in the blood, it could be used as a drug to increase the amount of brown fat in humans as well as its activity. </p>
<p>Before testing BMP8b in humans, we wanted to investigate the effect of boosting BMP8b in mice – that is, would it increase brown fat function? We genetically engineered the white fat of mice to have as much BMP8b as the brown fat of normal mice.</p>
<p>We <a href="https://www.nature.com/articles/s41467-018-07453-x">found</a> that increasing BMP8b levels made white fat browner and increased its activity. BMP8b does this by making mice more sensitive to the signals from nerves that activate brown fat. What was more unexpected was that BMP8b also increased the number of blood vessels and the number of nerves in white and brown fat. </p>
<p>This combination of factors was really exciting as BMP8b could make humans have more brown fat that has a good fuel supply. Increasing the number of nerves in brown fat would also mean any signals from the brain to activate brown fat would be amplified. Finally, because BMP8b makes brown fat more sensitive to signals from the nerves that activate brown fat, it may be possible to use drugs that mimic these signals at lower doses – even below the levels that cause heart attacks. </p>
<p>While our results are promising, more work will be needed to test if BMP8b can change brown fat function in humans.</p><img src="https://counter.theconversation.com/content/106283/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samuel Virtue receives funding from the British Heart Foundation, Medical Research Council and The Wellcome Trust. </span></em></p><p class="fine-print"><em><span>Antonio Vidal-Puig receives funding from MRC, BHF, Wellcome Truts, ERC and Horizon 2020</span></em></p><p class="fine-print"><em><span>Vanessa Pellegrinelli receives funding from the British Heart Foundation, Medical Research Council,The Wellcome Trust and WHRI-ACADEMY.</span></em></p>Scientists manage to boost brown fat in mice with a molecule called BMP8b. Could this be the future for treating obesity?Samuel Virtue, Senior Research Associate, University of CambridgeAntonio Vidal-Puig, Professor of Molecular Nutrition and Metabolism, University of CambridgeVanessa Pellegrinelli, Researcher, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/859872017-11-09T19:18:58Z2017-11-09T19:18:58ZCan ‘brown fat’ really help with weight loss?<figure><img src="https://images.theconversation.com/files/191334/original/file-20171023-26663-z1a0sy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">No, having a cold shower won't make you lose weight.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span></span></figcaption></figure><p>There have <a href="https://draxe.com/brown-fat/">been</a> <a href="https://www.scientificamerican.com/article/supercharging-brown-fat-to-battle-obesity/">hyped</a> <a href="http://www.abc.net.au/news/2017-08-14/increasing-brown-fat-by-exercising-in-the-cold/8796938">reports</a> <a href="https://www.rd.com/health/diet-weight-loss/brown-fat-boost-metabolism/">of</a> <a href="https://www.outsideonline.com/2054756/does-working-out-cold-burn-more-calories">late</a> <a href="https://paleoleap.com/cold-water-therapy/">about</a> “brown fat”. Different from the fat we mostly have (white fat), brown fat is capable of burning more energy. So the theory goes: if we have more brown fat, we can lose weight. But selective reporting and misinformation has blurred the lines between fact and fiction.</p>
<h2>What is brown fat?</h2>
<p>Grab that roll of fat on your stomach – that is white fat. The job of white fat is mainly to store energy, and then release it when other organs need it. We have much less brown fat which is hidden deep in the torso and neck. The main role of brown fat is to heat our body when we’re cold. To produce heat, brown fat cells expend (burn) energy. </p>
<p>Decades of <a href="https://www.ncbi.nlm.nih.gov/pubmed/14715917">research</a>, mainly in rats and mice, tell us when brown fat is “activated” from its resting state (for example, by cold exposure) it can burn a lot of energy relative to its small size. The potential for health lies in whether this energy-burning power can be harnessed to treat obesity.</p>
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<strong>
Read more:
<a href="https://theconversation.com/eight-diet-myths-busted-74259">Eight diet myths – busted!</a>
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<p>Brown fat’s presence in adult humans has been known for decades. While previously believed to have no function, in 2009 a <a href="http://www.nejm.org/toc/nejm/360/15">series of studies</a> showed it does burn energy when activated by short-term (minutes/hours) cold exposure. Our brown fat can’t burn as much energy as the brown fat in mice, and some evidence suggests its normal energy burning level is so low as to be irrelevant. </p>
<p>When brown fat is not “activated”, its energy expenditure is very low. The level of cold exposure and the amount of the skin surface exposed control the amount of energy expenditure. Most importantly, “training” brown fat forces it to become better at burning energy. But training involves weeks of daily cold exposure for several hours – something we modern humans rarely, or ever, do.</p>
<h2>Can cold showers activate brown fat?</h2>
<p>This new awareness of brown fat has, unsurprisingly, led to exaggeration of its purpose, function and benefits in humans. Cold exposure as a health fad has boosted this recent popularity. Common recommendations to activate brown fat are cold showers and (<a href="http://www.telegraph.co.uk/news/worldnews/northamerica/usa/11959130/Las-Vegas-spa-worker-found-frozen-to-death-inside-cryotherapy-tank.html">worryingly</a>), immersion for short periods in very cold (below -100°C) nitrogen gas. </p>
<p>Brown fat, like muscle, follows a “use-it-or-lose-it” principle and, as highlighted above, the more you use it the better it gets. Training brown fat requires cold exposure for <a href="https://www.ncbi.nlm.nih.gov/pubmed/28707455">several hours per day</a>. So brief periods such as a few minutes in the shower or a dip in nitrogen gas interspersed in an otherwise warm lifestyle are unlikely to train brown fat in a meaningful way.</p>
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Read more:
<a href="https://theconversation.com/do-ketogenic-diets-help-you-lose-weight-81810">Do ketogenic diets help you lose weight?</a>
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</em>
</p>
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<p>Should strong-willed devotees be willing to participate in hours of daily cold exposure, they will most likely increase their brown fat’s energy burning ability. But weight loss is unlikely to follow. Remember, the main function of brown fat is to keep you alive, not thin. During cold exposure, hunger is stimulated alongside brown fat activation to ensure there is adequate fuel for the fire.</p>
<h2>What about exercise?</h2>
<p><a href="https://www.ncbi.nlm.nih.gov/pubmed/22237023">Recent</a> <a href="https://www.ncbi.nlm.nih.gov/pubmed/24906147">studies</a> in mice show a role for regular exercise in the “browning” of fat (making white and brown fat become more brown). These studies suggest exercising muscles release hormones that make brown and white fat cells become more “brown-like”, meaning the fat cells can burn energy when activated by cold (noting that exercise itself does not activate brown fat).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191335/original/file-20171023-26688-10pq7e5.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>
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<span class="caption">Studies in humans did not find exercising increases brown fat.</span>
<span class="attribution"><span class="source">from www.shutterstock.com</span></span>
</figcaption>
</figure>
<p>But media hyperbole ignored current best evidence from exercise training studies in humans that show <a href="https://www.ncbi.nlm.nih.gov/pubmed/26189600">the opposite</a> – cold-stimulated brown fat energy expenditure is reduced. </p>
<p>And contrary to <a href="https://www.rd.com/health/diet-weight-loss/brown-fat-boost-metabolism/">recent</a> <a href="http://www.abc.net.au/news/2017-08-14/increasing-brown-fat-by-exercising-in-the-cold/8796938">reports</a>, exercising in the cold will not allow you to get fit and increase brown fat function at the same time.</p>
<h2>Nutrition supplements and medications</h2>
<p>Despite the promotion of supplements to increase brown fat development, there are currently no medications or supplements proven to increase brown fat in humans. Some <a href="https://www.ncbi.nlm.nih.gov/pubmed/23867622">evidence</a> suggests extracts from capsinoid-containing plants (such as chilli peppers) activate brown fat, but these have never been directly shown to increase human brown fat energy burning. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-we-can-change-our-body-shape-with-exercise-67642">How we can change our body shape with exercise</a>
</strong>
</em>
</p>
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<p>Our research also shows <a href="https://www.ncbi.nlm.nih.gov/pubmed/25725625">two</a> <a href="https://link.springer.com/article/10.1007/s00125-017-4479-9">drugs</a> that we and others thought would increase brown fat function, based on previous studies in mice and rats, actually decreased it.</p>
<h2>The future: brown fat in disease prevention?</h2>
<p>Understanding the role and relevance of brown fat for our health is at an early stage, and we have yet to discover its full capability. Being cold most of the time, for a really long time, will increase brown fat function, but there is currently no evidence for more suitable options, particularly ones that don’t also stimulate hunger. </p>
<p>We also don’t know whether brown fat activation directly improves health. Here the strongest evidence is that its function is reduced in <a href="https://www.ncbi.nlm.nih.gov/pubmed/19357405">obese people</a>. But whether this is either <a href="https://www.ncbi.nlm.nih.gov/pubmed/25725625">cause or effect</a>, and whether brown fat activation might reverse obesity remains unknown. Clearly there’s a need for more human research to uncover the facts.</p><img src="https://counter.theconversation.com/content/85987/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Carey receives research funding from the National Health and Medical Research Council of Australia, the Diabetes Australia Research Program and the Clive and Vera Ramaciotti Foundation.</span></em></p><p class="fine-print"><em><span>Bronwyn Kingwell receives research funding from the National Health and Medical Research Council of Australia and the Diabetes Australia Research Program.</span></em></p>Cold showers have been recommended to activate brown fat, but they are unlikely to yield any health benefit.Andrew Carey, Group Leader: Metabolic and Vascular Physiology, Baker Heart and Diabetes InstituteBronwyn Kingwell, Head, Metabolic and Vascular Physiology NHMRC, Senior Principal Research Fellow, Baker Heart and Diabetes InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/640622016-08-18T15:50:22Z2016-08-18T15:50:22ZDiabetes treatment could be revolutionised by making people cold<figure><img src="https://images.theconversation.com/files/134439/original/image-20160817-3573-19ayehp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cool science. </span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-174495806/stock-photo-winter-swimming-man-in-an-ice-hole.html?src=5a01ioRjlxTuVNhy0QDZGw-1-15">Levranii</a></span></figcaption></figure><p>For people in northern countries enjoying summer sun, I hate to put a dampener on things but winter’s coming. The cold months can seem to go on forever, yet scientists are uncovering a new reason to be grateful for them. </p>
<p>It turns out that cold climates may help keep type 2 diabetes at bay because of surprising findings about how temperatures affect certain “good” fats in the body. This insight potentially opens up exciting new means of treating people with diabetes – <a href="http://www.idf.org/about-diabetes/facts-figures">which afflicts</a> 415m people worldwide and is predicted to increase to 641m by 2040. </p>
<p>Strangely enough, this possibility arose from scientists trying to develop something else, namely a new major way of treating obesity. The two endeavours are linked in ways we don’t yet fully understand. To get a sense of how, you need to understand a bit about fat. </p>
<p>Our bodies have three types of fat: white, brown and brite. White fat cells are the body’s energy stores, <a href="https://books.google.co.uk/books?id=NIchAgAAQBAJ&pg=PT157&lpg=PT157&dq=white+fat+cells+20%25+25%25+men+women&source=bl&ots=54a8RDHYlM&sig=3P7skz_ZKysWgNAMStuteTEFIEc&hl=en&sa=X&ved=0ahUKEwjtutTIhMjOAhWgHsAKHRJjBMkQ6AEIIjAB#v=onepage&q=white%20fat%20cells%2020%25%2025%25%20men%20women&f=false">comprising</a> about a fifth of the weight of the average man and about a quarter of the average woman. Obesity is an excessive storage of this fat, and this increases the risks of type 2 diabetes. <a href="http://www.obesity.org/content/weight-diabetes">Almost</a> 90% of people with type 2 diabetes are overweight or obese. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134651/original/image-20160818-12303-n75acv.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>
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<span class="caption">That’ll be the white fat.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-345580751/stock-photo-hand-waving-american-flag.html?src=AF7pq4gTPGd-zD9crqNQWw-2-85">DONOT6_STUDIO</a></span>
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<p>Brown fat cells operate very differently. They are packed with <a href="http://www.newcastle-mitochondria.com/patient-and-public-home-page/what-mitochondria-do/">mitochondria</a>, which are rod-shaped organelles that are present in all cells. Mitochondria are often called the power houses of the cell for the way they convert nutrients in our food into a fuel source known as <a href="https://www.ebiomedia.com/how-cells-obtain-energy.html">ATP</a> that powers all cellular functions. Unusually, however, brown fat cells contain a special protein that when activated, restricts this conversion so that the energy is released as heat instead. </p>
<p>You find a lot of brown fat in small mammals like mice and rats that need lots of heat to regulate their body temperature. Human babies have it, too, but for a long time it was thought to disappear in adults, who can usually keep sufficiently warm through metabolic processes. In 2007, however, it was <a href="http://ajpendo.physiology.org/content/293/2/E444.long">shown that</a> adult humans do have functional deposits of these cells. This discovery is part of the reason for the recent excitement among obesity scientists. </p>
<h2>Great brite hope</h2>
<p>Brite (BRown in whITE) fat cells only came on the radar 25 to 30 years ago. <a href="http://jcs.biologists.org/content/103/4/931.long">Several</a> groups <a href="http://www.ncbi.nlm.nih.gov/pubmed/3453365">observed that</a> when small mammals are placed in the cold, their white fat deposits take on a browner appearance – a process we now call “browning”. Much more recently we <a href="http://www.cell.com/cell/pdf/S0092-8674(12)00595-8.pdf">realised that</a> these cells – also known as beige – come from a separate lineage to white fat even though they are related. </p>
<p>When brite cells mature they can act like either white or brown cells as the body’s needs change between energy storage and heat production. Scientists have been trying to understand this process, believing that if we can switch these cells into their brown phase, we may be able to activate them along with the body’s brown fat to burn off the energy stored in true white fat cells. Exposure to cold could be the key, since research has previously shown that this activates brown and brite fat in both <a href="http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1097-4652(199605">small mammals</a>167:2%3C285::AID-JCP12%3E3.0.CO;2-7/epdf) and <a href="http://www.ncbi.nlm.nih.gov/pubmed/27030666">humans</a>. </p>
<p>But will it work? <a href="http://www.nature.com/articles/srep30409">A paper</a> I recently co-authored sought to investigate this by analysing public health data. Our rationale was that if you can burn off excess white fat by increasing the sum of brown/brite fat in the body; and activate this through exposure to cold, people will on average be thinner in colder climates. </p>
<h2>America under the microscope</h2>
<p>Ours was not a completely new idea, but previous attempts were confounded by trying to compare different countries. Instead we focused on just one country – the US, <a href="http://www.worldatlas.com/articles/29-most-obese-countries-in-the-world.html">which has</a> one of the highest obesity rates in the world. </p>
<p>We recovered data on levels of obesity, type 2 diabetes, poverty, race and temperature from 2,654 of America’s 3,146 mainland counties, covering around 170m people. We found a weak correlation between the ambient temperature and obesity prevalence. </p>
<p>The average level of obesity in a typical northerly county with an average temperature of 5°C was 29.6% compared to 33.6% in counties further south with an average temperature of 25°C – in other words that big difference in temperature was only linked with about 1.1 times as much obesity. </p>
<p>Unexpectedly, though, the effect of climate on type 2 diabetes was much stronger. In the same two types of cooler and warmer counties, the prevalence of the illness was 1.6 times higher in the warmer ones (12.1% prevalence compared to 7.6% in the cooler counties). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=357&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=357&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=357&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=449&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=449&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134664/original/image-20160818-12274-28qo6i.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=449&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">John Speakman</span></span>
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</figure>
<p>It is not quite that simple, however. Warmer counties have higher populations of African Americans and are poorer, both of <a href="http://frac.org/initiatives/hunger-and-obesity/are-low-income-people-at-greater-risk-for-overweight-or-obesity/">which</a> are <a href="https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/338934/Adult_obesity_and_type_2_diabetes_.pdf">also linked</a> to higher prevalence of obesity and type 2 diabetes. When we factored this into the data analysis, it completely accounted for the disparity in relation to obesity. With type 2 diabetes, the temperature effect was reduced but still remained very strong. </p>
<p>The message seems clear: switching on your brown and brite fat may not do very much for your obesity levels, but it may have a strong impact on type 2 diabetes. </p>
<h2>The way ahead</h2>
<p>Despite our best efforts to control for confounding factors, it is always possible the data is being affected by something we overlooked. We were delighted therefore that while our paper was in review a small clinical trial <a href="http://www.nature.com/nm/journal/v21/n8/full/nm.3891.html">was published</a> in the Nature Medicine journal which showed enormous beneficial effects on insulin action from exposing type 2 diabetic patients to cold temperatures (15°C) for six hours per day. </p>
<p>The interesting thing was these benefits occurred despite only small changes in the patients’ brown and brite tissues. This suggests there is something special about being exposed to cold that may affect type 2 diabetes risk that we don’t yet fully understand. </p>
<p>So while this analysis suggests that the hopes of being able to treat obesity by switching on brown and brite fat tissue may turn out to be disappointing, something else exciting appears to be emerging instead. Patients with type 2 diabetes may see a major new additional avenue in treatment in the years ahead.</p><img src="https://counter.theconversation.com/content/64062/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The work referenced here was supported by grants from the Chinese government (Chinese Academy of Sciences).</span></em></p>Scientists thought they were closing in on one great new treatment but may have found another instead.John Speakman, Chair in Zoology, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/524682016-01-04T12:26:14Z2016-01-04T12:26:14ZStored fat is a feat of evolution – and your body will fight to keep it<p>In spite of the bad press, stored fat is actually a really wonderful thing. Without the capacity to store energy in the form of fat, we would have been unlikely to survive through millions of years of evolution and we would certainly look very different to the way we look today. We needed the capacity to store energy to survive periods of famine, and fat is a very sensible way to do this. </p>
<p>Even a relatively lean 75kg man <a href="http://www.ncbi.nlm.nih.gov/pubmed/22298655">typically has</a> over 100,000kcal stored in the form of fat. If we had to store this energy in other forms – for example as glycogen, the storage form of carbohydrate – our weight would increase by 40-60kg (because glycogen is less energy dense and also stored in combination with water). Imagine dragging around two packed suitcases while hunting or gathering and you’ll get the idea of why it has been so useful to package stored energy in the form of fat. </p>
<p>So, while fat is often demonised, it has also been our friend through millions of years of evolution. It makes sense for our bodies to store energy in this way and to develop systems to cling on to it just in case there is a famine around the corner. </p>
<p>But, our relationship with fat has changed. While some fat is essential and healthy, accumulating too much body fat has a detrimental impact on our health <a href="http://bit.ly/187CY1U">by increasing the risk</a> of chronic diseases. So, storing too much energy in the form of fat is clearly not a good thing. Sadly, most people are now storing too much energy as fat and <a href="http://www.who.int/gho/ncd/risk_factors/overweight/en/">many people</a> in the developed and developing world are now considered overweight or obese.</p>
<h2>Difficult to let go</h2>
<p>Excess stored fat is a particularly difficult problem to solve in part because we have evolved such sophisticated processes to protect fat stores once we have them. </p>
<p>One of the best-characterised physiological systems involves leptin, a protein secreted by our fat stores (adipose tissue) – that tells the brain that there is plenty of energy available stored in the form of fat. When discovered, there was a great deal of excitement about whether leptin could be administered as a treatment for obesity – perhaps in an injection that would trick the body into thinking that there were large amounts of fat available so that we do not eat as much. Sadly, these potential treatments were not effective and we now understand why. </p>
<p>As we store more and more fat the leptin level in our blood <a href="http://www.ncbi.nlm.nih.gov/pubmed/19190071">will increase in proportion</a> to the increase in stored fat. Our brains get used to this higher level of leptin, so administering more leptin over and above this higher level of leptin does not seem to help. Instead, it is when leptin levels fall that leptin becomes a very important signal. When we try to lose weight, there is a <a href="http://opus.bath.ac.uk/21470/">disproportionately large fall</a> in circulating leptin <a href="http://www.ncbi.nlm.nih.gov/pubmed/16979409">in spite</a> of only modest fat loss. </p>
<p>A fall in leptin is an attempt to defend fat stores with leptin functioning as the signal to the brain <a href="http://www.ncbi.nlm.nih.gov/pubmed/19190071">in a negative feedback loop</a> that maintains the stability of fat mass. A fall in leptin is associated <a href="http://www.ncbi.nlm.nih.gov/pubmed/9771856">with increased sensations of hunger</a> and an increase in <a href="http://onlinelibrary.wiley.com/doi/10.1038/oby.2009.228/full">“reward-related” behaviours</a>. Reduced leptin is also a trigger <a href="http://www.pnas.org/content/103/5/1593.full">for depressive symptoms in animals</a>. So, when we try to lose weight, our fat tissue sends signals to the brain to try to resist any further loss of fat; we feel hungry, we seek rewards, and we might feel a little down or depressed.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106651/original/image-20151218-27851-uijxfj.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">Not guaranteed to work if your hormones have anything to do with it.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-205640647/stock-photo-funny-overweight-man-jogging-on-the-road.html?src=8UvtQaWCoDXnMFAytTywcg-1-68">Weight loss by Shutterstock</a></span>
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</figure>
<p>What can we do about this? Well, <a href="http://www.nature.com/ncomms/2015/151120/ncomms9951/full/ncomms9951.html">a recent study</a> indicated that fat tissue may have some other properties that we might be able to manipulate to help. Some specialised types of fat cells (adipocytes) have the ability to burn energy to help keep us warm (a process called thermogenesis). The authors showed that this type of thermogenesis is normally turned off by a specific protein called sLR11. This makes sense because for millions of years we have been striving to store fat and only use it when there is a very good reason. </p>
<p>Interestingly, in this study, mice created without sLR11 did not gain weight when overfed because they burned more of the energy that was consumed. The authors also showed in a small number of patients undergoing bariatric surgery that the fall in sLR11 was related to the decrease in fat mass. Based on these observations, they suggested that sLR11 stops energy from being wasted via thermogenesis in fat tissue. By inference, if we can turn this off in humans then we might be able to get the body to use (waste) energy rather than clinging on to it. </p>
<p>Before we get too carried away, a caveat here is that this type of thermogenesis is mostly confined to certain types of fat cells (brown adipocytes <a href="https://theconversation.com/fat-burning-fat-exists-but-might-not-be-the-key-to-weight-loss-51081">or “brown fat”</a>) and these cells are more rare <a href="http://www.clinsci.org/content/69/3/343">and probably less important</a> in humans than in rodents. We can also achieve thermogenesis through other means such as burning energy through movement. We know that increasing thermogenesis through movement leads to a fall in leptin and that this probably explains why an exercise programme causes people to eat more and not lose <a href="http://opus.bath.ac.uk/21470/">as much weight as they should</a>. Whether burning energy through increased adipose thermogenesis will have the same effect in humans still also needs to be established. </p>
<p>So, for now, it is important to remember that when you feel yourself gaining a few pounds, your body will see this as a success and it will fight hard to keep any extra weight.</p><img src="https://counter.theconversation.com/content/52468/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dylan Thompson receives funding from BBSRC, MRC, British Heart Foundation, Diabetes UK, and Unilever. </span></em></p>Finding it hard to lose weight? Here’s why this may be.Dylan Thompson, Professor and Director of Research, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/510812015-12-16T10:57:23Z2015-12-16T10:57:23ZFat-burning fat exists, but might not be the key to weight loss<figure><img src="https://images.theconversation.com/files/105528/original/image-20151211-31729-vb3fu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tip the scale. </span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-312234413/stock-photo-weight-scale.html?src=XQPLLhpQHVlISbaWzKA4Rw-1-77">Scale image via www.shutterstock.com.</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>When you think about body fat, it’s probably white fat that comes to mind. That’s where our bodies store excess calories, and it’s the stuff you want to get rid of when you are trying to lose weight.</p>
<p>But white fat isn’t the only kind of fat in the body – you also have brown fat and beige, or brite, fat, which can actually burn calories instead of storing them.</p>
<p>Fat that burns calories instead of packing them on the body sounds like the Holy Grail of obesity treatment, and researchers want to find ways to activate or increase these types of fat in our bodies. In fact, the National Institutes of Health (NIH) has put out a call for research to figure out how to do it. But is the potential of brown fat to curb weight all it’s cracked up to be?</p>
<h2>So what makes brown and beige fat different from white fat?</h2>
<p>You might think that white fat just stores calories, but it actually does much more than that. It insulates the body, protects the internal organs and <a href="http://dx.doi.org/10.1210/jc.2004-0395#sthash.a7RdnIuU.dpuf">also produces</a> proteins that regulate food intake, energy expenditure and insulin sensitivity.</p>
<p>Brown fat is rich in mitochondria, which gives it a brown appearance. You may remember from high school science class that mitochondria are the “powerhouses” of the cell because they burn fatty acids and glucose for energy, releasing it as heat. That is why brown fat burns calories instead of storing them, like white fat does. White fat also has mitochondria, but not nearly as much as brown fat does. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1092&fit=crop&dpr=1 600w, https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1092&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1092&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1373&fit=crop&dpr=1 754w, https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1373&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/105873/original/image-20151214-9526-13h8qd9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1373&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">Brown adipose tissue seen in positron emission tomography (PET) scan.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/d/d4/Braunes-Fett-PET-17.jpg">Hellerhoff via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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</figure>
<p>Newborn babies have brown fat because it generates heat and helps them maintain body temperature. Rodents also have brown fat for the same reason. Until recently, it was thought that brown fat disappeared over the course of childhood. Now, thanks to advances in imaging technology, we know that adults also possess brown fat.</p>
<p>In humans, brown fat tends to be located around the neck and clavicle, but can also be found in a few other locations around the body. Weight can influence how active a person’s brown fat is, so the <a href="http://dx.doi.org/10.2337/db12-1430">more a person weighs</a>, the less active their brown fat is at burning fatty acids and glucose.</p>
<p>Beige or brite fat is made up of “brown-like” fat cells present in traditionally white fat deposits. Studies using animal models have shown these beige fat cells can form in white fat deposits under certain treatments, including cold exposure.</p>
<p>Whether these beige fat cells were preexisting white fat cells that turned into beige cells in a process called “<a href="http://ajpcell.physiology.org/content/279/3/C670.long">transdifferentiation</a>” or they are <a href="http://dx.doi.org/%2010.1038/nm.3324">brand new cells</a> is a point of contention among researchers. Like brown fat cells, beige fat cells appear to have the ability to burn fatty acids and glucose as energy.</p>
<h2>Calories in, calories out</h2>
<p>The principle behind weight loss or weight gain is called energy balance, which is the difference between energy intake (how many calories you eat) and energy expenditure (how many calories you burn). </p>
<p>Sticking to a low-calorie diet and an exercise-heavy lifestyle to lose excess weight isn’t always easy, so researchers have been looking for other ways to tip the energy balance in favor of expenditure. And some think that increasing the activity or quantity of brown or beige fat in the body might be one way of doing it.</p>
<p>This certainly appears to be the case in rodents. Studies have found that the chemical norepinephrine, cold exposure, diets and various proteins made in the body can all induce “browning” of white fat or activate brown fat to burn more calories in rodents. Most of these treatments also have some effect on energy balance, often increasing energy expenditure and causing weight loss. </p>
<p>Imagine if we could do the same thing in humans and transform the metabolically inert white fat that is weighing so many of us down into metabolically active brown fat that actually burns calories throughout the day. While it sounds like it could be a game changer in the fight against obesity, the research isn’t clear on how much of a difference brown fat might make for people.</p>
<p>For instance, some research has shown that activation of brown fat by cold exposure in humans translates to an increase in energy expenditure equivalent to less than <a href="http://dx.doi.org/10.3389/fendo.2012.00015">20 calories per day</a>, which is hardly enough to have the kind of effects on obesity that we all hope for. Other research has estimated that activation of brown fat in adults could burn up to <a href="http://dx.doi.org/10.1111/obr.12116/abstract">125 extra calories per day</a>.</p>
<p>The reason that activated brown fat makes a relatively small contribution to daily energy expenditure is unknown, though it may be because brown fat is present in the body in minuscule amounts compared the less metabolically active white fat. For instance, a recent study showed that out of 14 subjects, <a href="http://dx.doi.org/10.3389/fendo.2012.00015">only five</a> had more than 10 grams of activated brown fat.</p>
<p>And we also wouldn’t want to convert all of our white fat into brown fat, because white fat is actually something our bodies need. </p>
<p>For instance, in rare conditions in which there are no fat deposits, people often have insulin resistance, fatty liver disease and <a href="http://dx.doi.org/10.1007/s11892-013-0431-7">other metabolic complications</a>. This is partially due to the lack of proteins that are produced by the white fat, and also because the excess calories that should be stored in the fat have to be stored in other organs, such as the liver. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/105876/original/image-20151214-9526-1y3vmgd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Brown fat has more mitochondria than white fat.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-89509927/stock-photo-normal-healthy-brown-fat-left-image-and-normal-healthy-white-fat-brown-adipose-tissue-or.html?src=uv2-12pXYQAeD_lvd7_RFA-1-0">Brown and white fat image via www.shutterstock.com</a></span>
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</figure>
<h2>Brown fat might do more than burn calories</h2>
<p>Even if the data show that activating brown fat doesn’t seem to burn many extra calories in humans, it could have other health benefits.</p>
<p>Researchers <a href="http://dx.doi.org/10.1172/JCI62308">found</a> that transplanting brown fat from donor mice into the abdominal cavity of age- and sex-matched recipient mice reversed high-fat diet-induced insulin resistance, a condition that contributes to Type 2 diabetes in humans. </p>
<p>Other studies have shown that beige and brown fat has beneficial effects on glucose metabolism and insulin sensitivity that <a href="http://www.nature.com/nm/journal/v19/n10/full/nm.3361.html#t1">appear to be greater</a> than the modest effects on body weight. Brown fat has the ability to clear lipids (fats) and glucose from the blood, resulting in lower concentrations of circulating triglycerides, <a href="http://dx.doi.org/10.1038/ncomms7356">cholesterol</a> and glucose. This may contribute to the beneficial health effects of brown fat, independent of weight loss. </p>
<p>So future human research may lie in how these fats can positively influence <a href="http://dx.doi.org/10.1038/nm.3361">insulin sensitivity, or glucose and lipid metabolism</a>, rather than body weight. </p>
<p>There is much interest in being able to harvest the power of brown fat in humans to combat obesity and accompanying metabolic disease, but this research is relatively in infancy. </p>
<p>To help answer these questions, the NIH has <a href="http://grants.nih.gov/grants/guide/rfa-files/RFA-DK-15-031.html">announced grant opportunities</a> to identify conditions that trigger the “browning” of white fat, or increase quantity of brown fat in humans, find ways of testing for brown fat that don’t require needle biopsies, and explore the biological functions of these fats. This push means we should be learning more about this intriguing tissue soon.</p><img src="https://counter.theconversation.com/content/51081/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Desiree Wanders receives funding from the National Institutes of Health-National Institute of Diabetes and Digestive and Kidney Diseases. </span></em></p>The potential health benefits of energy-burning brown and beige fat might be not the effect on weight, but rather on blood sugar and cholesterol.Desiree Wanders, Assistant Professor of Nutrition, Georgia State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/226622014-02-05T15:56:06Z2014-02-05T15:56:06ZShivering unlocks new way of fighting fat<figure><img src="https://images.theconversation.com/files/40669/original/ynxscfvy-1391533912.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Shiver me timbers.</span> <span class="attribution"><span class="source">bmhkim</span></span></figcaption></figure><p>Shivering is not an activity many of us enjoy. We do it because we are cold and uncomfortable. But perhaps the news that it could have some of the same benefits as moderate bouts of exercise will stop us running in from the cold so quickly. Researchers have found that the act of shivering can stimulate the conversion of energy-storing “white fat” into energy-burning “brown fat”. </p>
<p>The findings, published in <a href="http://www.cell.com/cell-metabolism/retrieve/pii/S1550413114000060">Cell Metabolism</a>, show that when humans shiver their levels of hormones irisin (produced by muscle) and FGF21 (produced by brown fat) increase. Specifically, around 10-15 minutes of shivering by volunteers placed in temperatures of less than 15°C resulted in equivalent rises in irisin as an hour of moderate exercise.</p>
<p>Irisin, identified just <a href="http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10777.html">two years ago</a> in animals, converts white fat into brown fat. Unlike white fat, brown fat is designed to produce heat by burning calories. For example, around 50g of white fat retains more than 300 kilocalories of energy in the body. The same amount of brown fat could burn up to 300 kilocalories a day.</p>
<p>There has been a lot of excitement surrounding the discovery of irisin because the energy-burning nature of brown fat makes it a potential therapeutic tool for targeting obesity and diabetes. It appears to be a golden ticket to promoting a healthy metabolism: as well as burning calories, it drains the blood of glucose (useful for preventing the onset of type II diabetes) as well as draining blood of unhealthy fat like triglycerides.</p>
<p>Also through studies in the laboratory on animals, FGF21 has been found to be a powerful activator of this brown fat, energy burning process. It is a molecule that originates in the liver and in brown fat itself. Since brown fat was discovered in humans, researchers have been bent on <a href="http://www.bbc.co.uk/news/health-18996076">working out</a> how to stimulate more of it, which makes this new research particularly exciting.</p>
<h2>Unlocking our brown fat potential</h2>
<p>The capacity of brown fat to burn calories in order to produce heat and maintain body temperature in cold environments has long been known in animals. We are all born with supplies of brown fat; it is nature’s way of preventing hypothermia in babies. But <a href="http://ajpendo.physiology.org/content/293/2/E444">until recently</a>, it was thought to vanish in early infancy, getting replaced by “bad” white fat that sits on our waistlines. </p>
<p>We now know that brown fat is present in most, if not all, adults. Those with more brown fat are slimmer than those without. Glucose levels are also lower in humans with more brown fat. Efforts are therefore being made into understanding how brown fat is stimulated in humans. Previous studies have shown how irisin activates it in rodents; this research is an important step in understanding how it is stimulated in humans. </p>
<p>It was already known that cold temperatures stimulate brown fat, but a comprehensive knowledge on how the body signals that message to its cells was lacking. This latest study set out to better understand the mechanism underlying the activation of brown fat. </p>
<p>When we are cold, we first activate our brown fat because it burns energy and releases heat to protect us. When that energy is insufficient, our muscles contract mechanically, or shiver, thereby generating heat. But we did not know how muscle and fat communicate in this process. For the first time, this research shows the way that they communicate with each other through specific hormones – turning white fat cells into brown fat cells to protect us from the cold.</p>
<p>The identification of these two molecules, irisin and FGF21, as capable of promoting energy expenditure in humans, opens prospects for being used for potential drug developments. There is nothing better than promoting exercise as a healthy habit to enhance muscle production of irisin that will impair accumulation of calories as fat in our body. But, when exercising is difficult for clinical or personal conditions, knowing that enhancing certain hormones in the blood may promote energy expenditure could help develop more tools to combat obesity.</p><img src="https://counter.theconversation.com/content/22662/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Francesc Villarroya receives funding from Generalitat de Catalunya, MINECO (Spain) and European Union. He is affiliated with University of Barcelona and CIBERobn..</span></em></p>Shivering is not an activity many of us enjoy. We do it because we are cold and uncomfortable. But perhaps the news that it could have some of the same benefits as moderate bouts of exercise will stop…Francesc Villarroya, Professor, Department of Biochemistry and Molecular Biology, Universitat de BarcelonaLicensed as Creative Commons – attribution, no derivatives.