Synopsis: The body uses extra calories to stay warm in cold conditions, creating heath through thermogenesis. However, it’s only recently that scientists have discovered one of the mechanisms the body uses for this–brown fat. Now they’re learning how to harness brown fat for weight loss. Experts discuss.

Host: Reed Pence. Guests: Dr. Aaron Cypess, Acting Chief, Translational Physiology Section, National Institute of Diabetes and Digestive and Kidney Diseases; Dr. Francesco Celi, Professor of Medicine and Chair, Endocrinology and Metabolism, Virginia Commonwealth University; Dr. Wayne Hayes, Associate Professor of Computer Science, University of California, Irvine, visiting scientist, NASA Jet Propulsion Laboratory, and CEO, The Cold Shoulder; Adam Paulin, founder & Managing Director, Thin Ice.

Links for more information:

Thermogenesis and Weight Loss

Reed Pence: As the weather turns colder in much of the country, a lot of us will start putting on coats and jackets to stay warm outside. Keeping our body temperature up is something warm-blooded animals have to do to stay alive. And most of the time, our bodies can do it without any extra effort.

Aaron Cypess: In order to stay alive our body has to undergo millions of chemical reactions every second. A byproduct of those chemical reactions is the generation of heat. It’s actually the generation of heat that keeps the different reactions going. So, maintaining the cells, maintaining the heart, every time the heart pumps it’s generating a little bit of heat, every time the stomach processes nutrients heat is being generated. It’s what has to happen.

Pence: That’s Dr. Aaron Cypess, acting chief of the Translational Physiology section at the National Institute of Diabetes and Digestive and Kidney Diseases, part of the National Institutes of Health.

Cypess: We’ve been able to harness the heat that’s being generated by all the various processes going on in the body and able to regulate it very carefully. We achieve what we now know to be a normal body temperature, which is 37 Celsius or 98.6 Fahrenheit.

Pence: The body’s baseline heat production is called thermogenesis, according to Dr. Francesco Celi, Professor of Medicine and Chairman of Endocrinology and Metabolism at Virginia Commonwealth University.

Francesco Celi: A very basic definition is a resting energy expanded, or, which is the amount of energy that is needed to keep us alive without doing anything — just like an engine that is idling.

Wayne Hayes: Your body is burning calories every moment of every day just to stay alive, but if your body is even the slightest bit cold it needs to burn extra calories to maintain your body temperature of 98.6.

Pence: That’s Dr. Wayne Hayes, Associate Professor of Computer Science at the University of California, Irvine, a visiting scientist at NASA’s Jet Propulsion Laboratory, and CEO of the Cold Shoulder, a company that’s seeking to tap the science of thermogenesis to combat obesity. It’s really an enormously simple concept — if you’re a little bit chilly, it’ll help you lose weight.

Hayes:   The idea is that if your in an environment that’s even a little bit cold your body has to burn extra calories, but the colder the environment the more calories you’re going to burn. But of course, you want to still keep it comfortable if you’re going to use it as a weight loss device. There’s a range of comfort where you can burn more or fewer calories, but you don’t want people to shiver. That’s getting a bit too uncomfortable.

Pence: So if you want to go to work on a winter day with the heat turned off in your car, Hayes says go ahead. Or take a walk in the cold. You might lose a little weight.

Hayes:   That’s absolutely true, but you’d also have to avoid wearing your jacket in the car. So, you need to get into your car dressed in your normal everyday clothing, even a short sleeve shirt and shorts would be best. Just don’t turn the heat on. And, of course, you have to be careful; if it’s a really cold day out you don’t want to get frostbite. So, we actually recommend that if you do use a winter chill walk you only start with a few minutes outside in the cold at first to see how your body reacts. But yes, just sitting in your car on a cold day is another way to burn extra calories.

 Cypess: I don’t recommend anybody go and sleep in the cold or keep themselves uncomfortable in particularly cold environments right now. Because we don’t know what the overall benefit would be. Would either one of these lead to tens or hundreds of calories burned off a day, or is it going to be a more moderate amount that you could achieve by spending another ten minutes exercising? And so before we recommend people doing any of these kinds of things, we have to find out that it’s both safe and effective.

Pence: It may seem a little surprising that we know so little about using cold for weight loss… Or that amid all the weight loss books that exist, jumping into a pool of cold water hasn’t been suggested very often. The problem is that we didn’t know how to use cold for weight loss without making people shiver uncomfortably with cold. But Cypess says in just the last six years, we’ve learned that something else is keeping us warm, too.

 Cypess: We know that when we’re particularly cold, skeletal muscle will shiver and that shivering generates an enormous amount of heat, but the key thing is that when we don’t need shivering, when we’re not even aware that we’re cold, but we haven’t started to shiver yet, then other organs are also importantly involved in the generation of heat. One of those organs, which has only recently been discovered to be relevant in humans, is the brown adipose tissue or brown fat. It stores fat as a fuel. Brown fat stores fat for the rapid mobilization to generate heat.

Hayes: Your body has two types of fat: that’s the white fat that everyone’s familiar with that’s just like the marbling on a steak. But your body also has brown fat, and that is the type of tissue that literally generates the heat to keep your body warm. You have brown fat in your shoulders, you have some in your neck, and you have some across your back. Scientists have actually done experiments where they’ve actually put a thermometer into the skin into the brown fat to show that the brown fat is actually warmer than the rest of your body. It’s almost like a space heater or one of those old radiators that gets warm. It’s actually warmer then the rest of your body. Your blood picks up that heat and distributes it throughout your entire body, so that’s what brown fat does — it actually generates heat.

Pence: Hayes says that for decades, scientists thought that adults didn’t have brown fat. But new technology, PET scans of adults showing how the body metabolizes fuel, revealed that something was burning lots of energy in cold conditions — brown fat.

Hayes:   Smaller mammals have lots and lots of brown fat. So, for example a mouse has a significant amount of brown fat and baby humans have some brown fat. You might not know this, but baby’s actually can’t shiver. So if a baby is cold the only way it can generate extra heat to stay warm is through its brown fat.

Pence: Over the past few years, scientists have learned that brown fat is activated and starts burning calories in mildly cool temperatures. A room set to 64 degrees will do it if you’re wearing light clothing. So you don’t need to shiver to harness the power of thermogenesis. And that’s what makes it attractive.

Hayes:   If you are in what is called a thermo neutral environment, which is what we call room temperature — maybe around 70 – 75 degrees Fahrenheit, the kind of temperature where everyone feels comfortable, the brown fat is not activated. It’s not necessary because your body’s just doing stuff all the time just to stay alive. It’s digesting your food, your heart is pumping, there’s even friction in your veins and your arteries as the blood flows through. That all generates waste heat, and that waste heat, that normal amount of heat is what keeps your body at 98.6. But as the temperature of the environment decreases to maybe 65 Fahrenheit or below, that’s when your body has to burn extra calories to stay warm and that’s when the brown fat gets activated.

Cypess: We know brown fat is important from the studies that have been done using mice and rats. Activated brown fat can protect an animal from the development of obesity and it seems to help the cells that make insulin work better. Stimulating brown fat protects against the obesity that’s developed in the setting of a high-fat, high-carb diet.

Pence: How well does it work? Scientists aren’t precisely sure, but Celi’ work has given them some ideas.

Celi: By activating this response, we can expect to increase our energy burning by approximately 100 – 200 calories per day. And this is what we can do by doing half an hour of exercise.

Pence: But do people have enough brown fat to make activating it worthwhile? Cypess says scientists aren’t sure about that, either.

Cypess: Is it one percent of their total body, or what we’re seeing, at least in many people, it’s closer to half of a percent or even lower, and therefore the question we’re dealing with is, is the amount of brown fat you see typically in a person enough to generate heat, or are there other things going on? And then, secondly, if there isn’t quite enough right now, can we increase the amount of brown fat?

Pence: There are a couple of ways that brown fat could be increased in people. One is a brown fat transplant. Cypess says it’s been tried in mice, and works pretty well. The other way, it appears, is simply to repeatedly stay out in mild cold until you get used to it. If you get acclimated to cold, you may be growing brown fat.

 Cypess: If one gets mild cold exposure over a period of time, the brown fat gets more effective at generating heat. That’s really exciting because it’s good to know that it’s there and you can activate it once. But the fact that multiple rounds of activation can lead to its growth is really good. The analogy I would give is to exercise for your muscles. You can lift weights or run a few miles and your body gets the exercise. Then as the muscles get used more often they get bigger they get stronger, they get more effective, and that’s the same thing that we think about brown fat — the more often you stimulate it the more effective it is.

Pence: That’s the property that several firms are banking on in their quest to harness the power of thermogenesis. Hayes’s company, the Cold Shoulder, manufactures a vest equipped with frozen gel packs strategically placed in the shoulders and upper back where there are few nerve endings and where brown fat is known to reside. Hayes says wear the cold shoulder vest a few hours a day and you’ll burn calories without trying, and without being uncomfortable.

Hayes:   Unlike drugs, if you take a drug your body at some point develops immunity or develops a tolerance to drugs. With cold exposure your body does get used to it, but in that case it actually becomes more effective rather than less effective because your body gets used to the idea of turning on its internal furnace to burn calories. So the more you wear the vest, or the longer you wear the vest for several weeks in a row, for example, it’ll become more effective rather than less effective, so it’s quite an awesome idea.

Pence: Another firm, Thin Ice, produces a vest and even insoles to trigger thermogenesis. Adam Paulin is the company’s founder and managing director.

Adam Paulin: You only need to stimulate specific parts of your body that have what are called thermo receptors. Thermo receptors are the neural tissue that lets you capture cold temperatures and tell your brain that you’re cold. So, if you’re able to stimulate enough of these areas of the body, then your brain perceives itself to be cold and the whole process of thermo genesis starts naturally. You don’t actually have to feel to the point of shivering to actually see results.

Pence: But it’s not like someone can put an ice pack in an insole. So Thin Ice uses electronics to produce the feeling of cold.

Paulin: The technology you’re referring to are called Peltier cooling chips. They’re used right now mostly in electronics to cool down microprocessors and things like that. What they do is pump heat from one side of the chip to the other side. That’s all they do, so the effect on the body is that it’s pumping heat away from the body constantly and then we dissipate that heat. It’s just basically an ongoing cycle. On the feet we have about five of those that are stimulating different parts of your feet that have a lot of thermo receptors. That’s an ongoing process throughout the day and its battery powered, which you can recharge.

Pence: Both Thin Ice and Cold Shoulder say their products, if used for eight or 10 hours a day, should burn between 500 and a thousand calories per day — enough to lose a pound or two per week, all other things being equal. Studies that quantify results don’t satisfy most scientists, but Celi, who keeps his office at 64 degrees, is a believer.

Celi: Well, it does work; it does work in terms of increasing the brown fat activity and in the long run by increasing brown fat activity there is an increasing brown fat mass. So it’s a positive reinforcement.

Pence: But before that long, it may not even take a cold vest to activate brown fat for weight loss. A drug for overactive bladder that’s already on the market has been found by Cypess’s group to stimulate brown fat in mice…leading to big reductions in obesity. So, it’s possible that a process that we knew existed only six years ago may ultimately lead to the dream of many… a pill that really helps people lose weight. To tap the power of thermogenesis for now, though, it may take driving to work with the heat off and the windows open… leaving your nice warm coat behind. You can find out more about Cold Shoulder at More information about Thin Ice is at You can learn more about Dr. Aaron Cypess’s work at… And information about Dr. Francesco Celi is at You can find out about all of our guests through our website,, where you can also find archives of our programs. You can also find them on iTunes and Stitcher. I’m Reed Pence.

Join the discussion

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.