Image Credit: Pyh2 / Wikimedia Commons. This image has been modified.

Brown Fat: Losing Weight through Thermogenesis

During World War I, it was discovered that many of the chemicals for new explosives had toxic or even lethal effects on the workers in the munitions factories. Chemicals such as di-nitro-phenol (DNP) can boost metabolism so much that workers were too often found wandering along the road after work, covered in sweat with temperatures of 106 to 109 degrees Fahrenheit before they died. Even after death, their temperatures kept going up, as if they were having a total body meltdown. At subacute doses, however, workers claimed to have grown thin to a notable extent after several months working with the chemical.

That got some Stanford pharmacologists excited about the “promising metabolic applications” of DNP. Our resting metabolic rate jumps up 30% after one dose of DNP, and therefore, it becomes an actual fat-burning drug. People started losing weight, as you can see in my video Brown Fat: Losing Weight Through Thermogenesis, with no apparent side effects. They felt great… and then thousands of people started going blind and users started dropping dead from hyperpyrexia, fatal fever due to the heat created by the burning fat. Of course, it continued to be sold. Ad copy read:

“Here, at last, is a [weight] reducing remedy that will bring you a figure men admire and women envy, without danger to your health or change in your regular mode of living….No diet, no exercise!”

It did work, but the therapeutic index—the difference between the effective dose and the deadly dose—was razor thin. It was not until thousands suffered irreversible harm that it got pulled from the market and remained unavailable. Unavailable, that is, until it was brought back by the internet for those dying to be thin.

There is, however, a way our body naturally burns fat to create heat. When we’re born, we go from a nice tropical 98.6 in our mother’s womb straight to room temperature, just when we’re still all wet and slimy. As an adaptive mechanism to maintain warmth, the appearance of a unique organ around 150 million years ago allowed mammals to maintain our high body temperatures.

That unique organ is called brown adipose tissue, or BAT, and its role is to consume fat calories by generating heat in response to cold exposure. The white fat in our bellies stores fat, but the brown fat, located up between our shoulder blades, burns fat. BAT is essential for thermogenesis, the creation of heat in newborns, but has been considered unnecessary in adults who have higher metabolic rates and increased muscle mass for shivering to warm us up when we get chilled. We used to think brown tissue just shrank away when we grew up, but, if it was there, then it could potentially make a big difference for how many calories we burn every day.

When PET scans were invented to detect metabolically active tissues like cancer, oncologists kept finding hot spots in the neck and shoulder regions that on CT scans turned out not to be cancer, just fat. Then, some observant radiologists noticed they appeared in patients mostly during the cold winter months. When they looked closer at tissue samples taken from people who had undergone neck surgery, they found it: brown fat in adults.

The common message from a number of studies is that BAT is present and active in adults, and the more we have and the more active it is, the thinner we are. And, we can rapidly activate our fat-burning brown fat by exposure to cold temperatures. For example, if you hang out in a cold room for two hours in your undies and put your legs on a block of ice for four minutes every five minutes, you can elicit a marked increase in energy expenditure, thanks to brown fat activation. So, the studies point to a potential “natural” intervention to stimulate energy expenditure: turn down the heat to burn calories (and reduce the carbon footprint in the process).

Thankfully, for those of us who would rather not lay our bare legs on blocks of ice, our brown fat can also be activated by some food ingredients such as those that are covered in my Boosting Brown Fat Through Diet video.

I briefly touch on the role cold temperatures can play in weight loss in The Ice Diet and talk more about calories in (Nutrient-Dense Approach to Weight Management) and calories out (How Much Exercise to Sustain Weight Loss).

In health,

Michael Greger, M.D.



Michael Greger M.D., FACLM


42 responses to “Brown Fat: Losing Weight through Thermogenesis

Comment Etiquette



The Short List




View the Full Community Guidelines

  1. In my previous life I did CT scans in a hospital environment. You can see fat very plainly on scans and I always thought it strange how fat was distributed thru out the body. An over weight teen or young adult would have a huge amount of subcutaneous or just under the skin fat and what looked like a normal little body inside. Then there was the older person with a huge belly and in the scan the organs were just swimming in a sea of fat but very little under the skin… It became obvious that the people with the organs surrounded by fat were the ones that had more disease..
    Just an observation…

    1. Hi Mitch, I appreciated your observation. It seems reasonable to me that as we gain fat it builds up subcutaneously and then continues to accumulate around our organs. One of the common complaints of my patients as they lost weight was they would lose it first in their face, arms, breasts… etc. and lastly where they wanted to lose it the more… belly, hips. There is variability in the distribution of fat cells in persons accounting for different “shapes”… got to love variability in populations. The secret to losing fat is the “ad libitum diet”… eat when you are hungry just less energy dense foods. The best presentation I have seen on this is by Jeff Novick RD which can be viewed free at…… entitled Calorie Density: How to Eat More, Weigh Less and Live Longer. Keep tuned to as the science just keeps coming. Thanks for your post.

    2. Main variable there is AGE?

      I’d also like to see the issue of thyroid function in relation to fat burning….and I mean REAL thyroid function not the typical established medical version measure.

  2. I recently read an article that suggested COLD SHOWERS in the morning as a road to self improvement. Better at getting us going than coffee.

    Could this be? Could it be related to activating higher rates of metabolism?

      1. Exactly. The development of BAT and learning voluntary control of thermogenesis is a big part of his method. See /What Doesn’t Kill Us/ by Scott Carney or Google “Wim Hof Method.” It really works. People who live in cold climates have known about this for centuries. E.g., Thoreau cites several examples in /Walden/.

    1. I live in the south and I recall when I was cold and wet up North, I would shake like crazy. This shaking would burn calories and I assume would burn energy to keep me some semblance of warm… Maybe the cold shower would do the same thing??
      The only thing a cold shower did for me was make me uncomfortable and kill my sex drive! ;^)

    2. Cold showers or buckets of ice cold lake water over the head is a Russian tradition. I first heard about it through the Russian Martial Art Systema.

      Hot water and hot environments increase blood flow to the extremities and to the surface of the skin, cold water and cold environments do the opposite and draw blood towards the core of the body. These effects can be exploited to the benefit of the circulatory system and lymphatic system.

      I have used this method locally on severe bruising and swelling that resulted from injury. Applying heat then cold to the affected area repeatedly will reduce any bruising or swelling significantly. I’m sure it would do the same for the body but I wouldn’t go heating the whole body before taking a cold shower as that could have serious health implications and may put you in shock.

  3. I have been eating Dr Greger and Forks Over Knives diet for 17 months, not overweight when I started I still have the podgy stomach and big waist. At 138 pounds, 5’8″ tall and 68 years old I am a good weight but that wretched fat down my front – nowhere else!!! I do wish it would go away.

    1. Hey Maureen,

      That can be a difficult area to lose weight in. Adding light exercise such as walking 30 minutes 5 days a week can be really helpful in targeting extra fat. It sounds like you are already eating a healthy diet; just make sure you’re eating the right amount of calories for your age, BMR, and BMI for healthy weight loss. Good luck!

  4. This must have something to do with why a fat family I know can’t stand having the house at a temperature I would find comfortable. Also why the man in the family, who weighs 300+, wears shorts all winter. It has always seemed to me that their exposed skin should be cold even if the rest of their bodies were warm, but apparently it isn’t.

    1. hi Daniel Wagle, I believe you are a long time follower of Dr Greger, so there probably isn’t much new that I could tell you, but I can share my personal experience. I have stayed slim for decades using a simple principle of not insisting that I feel comfortable. In short, it works for me to feel cold, tired and a bit hungry often. That is, when its a rainy, 36F November morning, I am on the trails hiking the hills instead of sitting by the fire having tea. A little bit hungry tells me I am short a few calories, and some fatigue tells me I have had my daily exercise quota. It all seems to work together to make it easier and with less effort, to stay in the slim zone. All the best in health to you !

  5. There are several ways to lose fat and weight:

    – Keep the home temperature low because the body has to spend more energy to keep the body warm.

    – Consume hot pepper which contains capsaicin,.

    – Consume foods which contain L-arginine which helps battle obesity by minimizing visceral adipose tissue (belly fat).

    – Maintain a good metabolism by having good nutrition, and in particular eating good fat. Yes FAT. Because eating fat does not make you fat, just like eating spaghetti does not make you thin like a spaghetti. Because when you have good metabolism, you body burns fat even in your sleep. The calorie counting method for weight loss does not work because it starves people, and therefore they have low metabolism. Yes, it is counter intuitive by eating more healthy foods to lose weight, in particular healthy fat.

    – And there is a method for healthy fasting, i.e. bu eating no foods but only consuming bone broth. Because you will get all the proteins, vitamins and minerals while eating no solid foods and you will lose weight without losing your health. And one more important thing is that bone broth contains all amino acids, and in particular an abundance of L-arginine.

    1. Jerry Lewis, have you read “The China Study”? I read it and cut out ALL animal products and lost 30 lbs. Then when I cut out OLIVE OIL, I lost 5 additional lbs. That’s why I think what you’re saying is not right.

      1. The concept of eating fat will make you fat, is not only so wrong but also so damaging to people. It’s actually the reverse. Because it actually makes you thinner because fat is used as fuel, and not only it helps your brain, it also helps your metabolism which helps you burn … fat, even in your sleep. If you can see me then I am skinny and semi muscular, and have not even an ounce of fat around my belly or any part of my body. And so is my family, and all of our friends and relatives who eat fat. I am glad to see that the younger generation has debunked this obsolete fat theory and they are perfectly healthy. Go to any healthy food stores to see what they sell.

        It’s the sugar and not eating enough fat that makes the body store fat, that makes you fat.

        Being fat is unhealthy but eating fat is not. There is a big big difference between the two.

        As a vegan, you can eat as much avocado as you want and see for yourself that you will get thinner. Don’t eat too much nut and seed for the fat because this is PUFA fat which causes inflammation. But avocado fat is perfectly healthy. Olive oil is too if it is not rancid. Coconut oil is good too if you are not scared of this obsolete “saturated fat” theory. Vegetable oil is an obsolete NO NO because it becomes rancid and changes to transfat easily. It is sad that Whole Foods, now owned by Amazon, is pushing for canola oil. So wrong and so harmful.

        1. WRONG….

          Your reply leaves much to be desired, because so much of it is just plain false. There is no benefit in eating olive oil. If one likes, one might eat the olive–but the oil has ONLY CALORIES and none of the fiber and nutrients that the olive has. This is what you are missing when you say it is okay to eat olive oil.

          As to coconut oil, the same thing is true–if you eat some coconut, that may be okay, but the oil, once again, is the extract of a whole food, and as such, contains ONLY CALORIES and none of the fiber and nutrients found in coconuts.

          And once again, I state that I lost 5 pounds just by eliminating oil from my diet.

          You say fat is used as fuel, but so are carbs and protein. Just about all whole foods have fat in them–even lettuce. There is NO NEED to ADD fat into one’s diet in the form of oil at any time.

          1. You ate the wrong fat earlier, such as vegetable oil. And when you said that you lose weight after going vegan, it was perhaps because you ate the wrong animal foods such as processed foods, and you didn’t eat WFPB earlier – nobody ever said that eating animal foods means excluding eating WFPB. It’s WFPB + WFAB.

            Study more about how olive oil is made or become rancid or faked before trashing. We don’t get to eat the real olive unless it is canned.

            And last coconut oil having no fiber is laughable. Of course you will get the fiber from eating other foods. You don’t just gulp coconut oil by itself. It’s just Dr G explanation that other cultures that eat coconut and have no problem because of the fiber.

            1. You are wrong about me eating the wrong foods. I was eating foods I prepared myself, and when I started eating WFPB, that’s when I lost the weight. Oil is BAD with regard to losing weight, which I know from personal experience. You are a relative newcomer on this site. I encourage you to read “The China Study” and “Whole” which you have probably not done yet. That will clarify some of the information about oil as well as other foods. Oil is not something one can just go and harvest. Oil is not a natural food. People should not eat oil–even WITH whole foods.

              1. Re: You are a relative newcomer on this site.

                LOL. This says it all. I read this site probably longer than you do. I used to be a fan of Dr G until I found out about so many wrong that he preaches. I still follow him because most of the time he is correct but I read also a lot from other places to make up my mind.

                I don’t know you but I bet that it is 99% that I know more about WFPB than you do and I eat much more than the daily dozen than you and most people.

  6. Can someone at NF PLEASE do something constructive about this distracting, egotistical, offensive, know it all who has taken over and polluted the comment section with his counter-productive, biased, opinions for far too long! This has always been a place to come for factual science education, but he is ruining the experience with his negative, nonstop, biased, opinionated, personal BS! Enough already!

    1. Dude calm down. Jerry Lewis is always fun to read even if he’s kind of a troll sometimes. Lighten up- I don’t think anyone is basing their life on what he says. People can make their own decisions. Being angry isn’t healthy either.

      Jerry Lewis: I think you’re wrong about coconut oil but I respect you as a human being. Yay!

      1. The real issue is how people are spending their time?

        Fact is that whether anyone wins some inane argument on a forum WILL NOT make much difference 15-20 years down the line as far as their health.

        It is WHAT YOU LEARN and actually APPLY effectively to your life that is going to make a difference over time. And time is of the greatest importance…because the sooner you understand what is effective and apply it…the more likely you see the benefits.

        The comedian is wasting his and other people’s time and attention with his mostly simpleminded arguments that more or less take up space.

        If you think his distractions are entertaining…I’d say that you are functioning on the same level.

        1. I’d say his distractions are dangerous to people who are trying to learn because although he is not a medical person, he answers questions as if he is–and we know a lot of the answers he provides are wrong according to current understanding of the science.

      1. Marvin, the problem is that the troll feeds unknowing or new readers information that is not supported by science. And then the new readers ask the troll questions, not knowing that he is a troll. I don’t feel that we should stand by while the troll feeds out information not supported by science.

  7. How does this fair for a person who is anemic and/or sensitive to cold environments? I find it fascinating how everyone internal temperature is different on a given day. I will still review the video. Thanks for any responses.

  8. I live on the Pacific coast in CA and yearly, around late May, I start to swim in the ocean once it gets >60F.
    I start off just head up breast stroke for as long as I can stand it. Not much exercise at first… but my body temp. gets lowered and it takes a few hours to get back to normal. I lose 3-5 lbs fast (burning all those calories to get warmed back up) in the first month then eventually gain it back as muscle built up from
    the exercise as I gradually swim further and further.

    My point is: If you are overweight, go into the cold water daily and you will lose mucho weight as you will burn a lot of calories just warming back up. No need to take a drug to burn pounds off, no need to get hyperthermic, etc.

Leave a Reply


Pin It on Pinterest

Share This