A Primal Primer: Brown Adipose Tissue
Last week’s Dear Mark discussing cold thermogenesis got some of you asking about brown adipose tissue. It’s a topic that deserves a full-fledged Primal Primer, especially since the idea of “good” body fat, a term many use to describe brown adipose tissue (BAT), is a foreign one. I mean, we’re talking about body fat here. Who wants it? Everyone I know is trying to get rid of their adipose tissue, not obtain more. It’s what brings many to this blog and what initiates this grand journey toward health and wellness. Even the people who say they “don’t care” about how they look would rather not have excess body fat, if only because it’s a marker of poor health or hormonal disregulation. We might acknowledge that we technically “need” some body fat to survive, but most of us will pass on any more than is absolutely necessary, thank you very much.
So whenever brown adipose tissue is invoked as the “good” kind of body fat, a body fat that cannibalizes other body fat, flabbers audibly gast. Is such a thing even possible?
Yes. Brown adipose tissue is very different than white adipose tissue. While white body fat can be regarded as an endocrine organ involved in the release of hormones, it doesn’t “do” all that much. It leads a pretty sedentary existence. Brown adipose tissue is metabolically active, however, consuming fat and glucose, increasing metabolism, and generating warmth for the organism as needed. Animals without the ability to shiver or tie scarves around their necks – like rodents and newborns – have lots of brown fat, because that’s how they stay warm – through “non-shivering thermogenesis.” Brown fat is dense with mitochondria, the power plants of cells which normally use fat and glucose to produce ATP. BAT mitochondria use fat and glucose to produce heat, rather than ATP. Thermogenin, or UCP1, is the uncoupling protein within the mitochondria that enables BAT to oxidize fat without producing much ATP.
Until quite recently, researchers assumed brown fat was mostly absent in adult humans. And if adults did have any, it was probably just a vestige from childhood with little actual functionality. In actuality, recent studies show that men and women can and do have significant amounts of brown fat, usually located near the neck, the chest, and the upper back, with women tending to have more than men. Rather than being inert, this adult brown adipose tissue is metabolically active with some interesting potential effects:
- If “cold exposure” is indeed a proxy for “brown adipose tissue activity,” as I suspect, it clears triglycerides from the blood once the fat in the BAT has been depleted.
- It is inversely correlated with obesity. The more body fat you have, the less BAT you have and the less activity you show in the BAT you do have.
- It is correlated with bone mineral density. Low, or nonexistent levels of brown fat are strongly linked to low bone mineral density.
- It is inversely correlated with fatty liver.
That all sounds pretty good, but how do we act on this knowledge? Is there anything we can do to start utilizing brown adipose tissue in our pursuit of health, leanness, and general Primal awesomeness? Maybe.
If you want to activate BAT, you have to get cold. Seeing as how brown adipose tissue’s primary function is to maintain body temperature, cold exposure activates existing brown fat – it presents the necessary environmental stressor to tell brown fat to start burning triglycerides for energy. A recent study (PDF) found that while exposing both lean and overweight men to “mild cold exposure” (61 degrees F, or 16 degrees C) activated brown adipose tissue in 23 out of 24 of them, thermoneutral temperatures resulted in zero BAT activity. Your brown adipose tissue doesn’t have much to do on a nice, warm day – nor, for that matter, on a miserably cold day so long as you’ve got the heater on inside.
Get cold, but not so cold that you can’t stand it without breaking down into a shivering mess. Brown fat keeps us warm up until the point of shivering, after which the physical act of trembling warms us and brown fat is deactivated (or down-regulated; it’s not clear whether it gets flipped off or gradually fades away). If you want to activate your BAT and only your BAT, don’t get so cold that you begin to shiver. Eventually, of course, your “shiver set point” will improve, you’ll get used to the cooler temperatures, and you’ll be able to tap into your BAT at lower and lower temperatures. Shivering also burns calories in its own way, but, well, shivering is kind of unpleasant and awful and it requires far lower temperatures. Go for goosebumps.
Although cold exposure is definitely the best way to activate brown fat, there’s also evidence that a person’s brown fat stores mediate the amount of energy they store after eating. Whenever you eat something, heat is generated, both from the physical and enzymatic breakdown of the food and from “diet-induced thermogenesis.” In patients with lower UCP1 expression (remember, UCP1 is the protein that enables combustion in the brown adipose tissue), the thermogenic response to a meal is lessened; and patients with confirmed brown adipose tissue generate more heat in response to a meal than patients without brown adipose tissue. Since that heat comes from energy that is not being stored, a greater thermogenic response to food means less (bad) body fat accumulation.
All this revolves around the activation of existing brown adipose tissue. While that’s important, what about creating new BAT? There are two candidates – chronic cold exposure and exercise.
In rodents, temperature to which the animal is chronically exposed determines the total amount of BAT on the body. Rats in a heated lab will have less brown fat than rats living outdoors. Humans, even those living in cold climates, are rarely exposed to the cold weather. They sleep in heated homes, drive in heated cars, shop in heated department stores, and bundle up with multiple layers for those fleeting moments spent outdoors. It’s even been proposed that the advent of central heating is related to obesity. I suspect that the total amount of human BAT also depends on chronic exposure to cold, especially since one study (PDF) showed that outdoor workers have more BAT than indoor workers. Acute exposure activates, chronic exposure creates.
Irisin, the “exercise hormone,” appears to convert white adipose tissue to brown adipose tissue. As irisin increases in a rodent’s blood, energy expenditure increases without an increase in movement or food intake, suggesting an increase in thermogenesis mediated by the converted WAT. Humans also make irisin in response to exercise, so this could work for us, too.
I don’t think we can ignore brown adipose tissue as a partial player in the metabolic mess we’re in. It’s not the one key to solving the obesity epidemic, but neither is anything else. It’s a piece of the puzzle, a contribution to the whole mess, and it’s completely plausible to think that people are fatter than they have to be because they’re too dang warm all the time. Sure, people have always avoided the cold, whether through central heating or animal pelt, but the way we avoid it today is way different – and far more effective. At any rate, it can’t hurt to give it a shot.
Hopefully, one of these Saturdays I’ll be able to include a recipe for stir-fried veggies in the rendered brown fat of pasture-raised hamster (sorry, hamster lovers; I had to pick a rodent). Until then, let’s hash things out in the comments. Tell me about your experiences with cold exposure, brown fat, and weight loss, or weight gain, or your plans to experiment. Take care!
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Posted By: Mark Sisson
Interesting. California beaches are right around 55-63 degrees.
Time to hit the surf after work more often
Yes! For years I’ve advised people to stop avoiding every inkling of temperature extreme as warming you up or cooling you down revs metabolism. Nothing is more annoying than watching overweight people pre-heat their cars with automatic starters every cold winter morning. Same goes for all the women that refuse to go in or stay in the water at beach or pools…
Mark, you know what is funny? They usually label you like accessible…But as a medical student, I have to say you are very well informed, and the ability to communicate extensive research in such a simple and appealing way shouldn’t hide the fact that you truly understand the topic! I usually try to re-check everything, but you do it for me. Thanks for Your books and articles.
What about people who live in chronically hot places? Like Florida? Does cooling the body also burn calories?
I’m not sure if it was intentional but I find it funny that in the picture that shows the definition of fat, it has corpulent, pudgy and also profitable, rich. The government that influences the health authorities which recommend high carb diets is making America corpulent and pudgy while making them rich.
I feel far more energized in cold weather than I do in hot weather. Hot, humid temperatures make me tired and aggravated.
Great job on your blog! Have you considered eating “primally” while continuing to bodybuild? Also, you documented your weight and body fat stat…one question that came to mind is “What is your height?”
This was covered in the 4 hour body. Was very interesting reading. I know take cooler showers although I HATE being cold which is a very standard condition for me since I’ve lost weight.
It’s rather unpleasant to adapt to cold water, but the feeling when you leave the shower after “cold session” is great.
Hmm … I get cold and tired after eating, to the point where I need to go wrap up in bed after anything more than 10 bites of food. I can’t seem to regulate my body temp at all anymore, I’ve seen doctors about it. I tried the HCG shots last summer just to see if I could burn off the “right” kind of fat; they were thinking I didn’t have enough of the keeps-you-warm-around-the-organs kind. I eat very little and am very overweight anyway. I wonder if it’s anything to do with my fat type ratio, and if so, how would I go about fixing it? I am already cold all the time so whatever brown fat I have must be worn out.
Hmm, sounds like me after eating rice 2 days running. I think I’m very allergic to the stuff. Good thing it’s now a rare item of diet. Ever think of trying an Elimination Diet? Results might shock you
no end.
Wait, WTF? I grew up in eastern Washington (snowy) and the San Francisco bay area (foggy and wet). When I moved to Sacramento (hot as hell for six months of the year), I gained 100lbs. I moved back to the bay area and lost 70lbs doing basically nothing different. I got pregnant and gained the 70lbs back, then moved back to Sacramento and could not get the fat to budge until I found paleo / primal. For years, I’ve joked that the hot weather makes me fat.
Now… Are you telling me that the hot weather really is making me fat?!
This past winter, I kept the house pretty cold, like around 55. It wasn’t for my health: I have a wood heater with heat pump back-up, and I just didn’t want to build a fire on some days b/c it took time. But I didn’t want to pay the electric company either. I got used to it, and I did lose some weight. Some of that weight has crept back on this summer, but not much. I have also noticed that when other people are cold, I am not: I was on a plane recently when most people felt too cold, but I felt fine. Maybe my brown fat kicked in and warmed me up.
Huh. I always complain about the cold. Would anyone know why I would generally feel colder (i lived a year in south Texas but that was years ago) than most people and prefer warm climates, and also I’ve noticed on mornings when I eat eggs fried in coconut oil with Bacon or fish and a whole sweet potato I feel warmer and and seem to have more energy.
Amazing…..So things actually make some sense now. I was wondering why sometimes even in ketosis, some people still gain or lose weight while trying to maintain (regardless of water retention) Mark is the man!
When I overeat I feel like I’m burning up from the inside out. I feel like I could spontaneously combust, and I’m fat….. My husband is thin and never feels hot after a meal. So I don’t know, it’s opposite in us. I’m going to start taking cold baths/showers before bed and see if that can speed my weight loss along. I hope! Atleast it should make me sleep better since i’m also burning up when sleeping.
Nice, reading this from the cold shower.
Have been doing the cold shower (after regular hot shower) every day for the last 2 months. Also, taking advantage of our chilly mornings here in the NW. Drive around with the windows down, get to goosebump stage. The cold showers have become very addictive, they make me feel so good, but I have not really noticed a reduction in fat, still have that last 10 pounds to shed and it is going pretty slow.
maybe we should alternate cold and hot showers. any advantages to hot showers, other than the enjoyment?
I am another one of those “crazy Russians” living in the U.S.:-). Every night after a hot shower I dump a bucket of cold water on my neck/ back. It feels AWESOME and I NEVER get sick.
Here in the far north I spent 3-5 hours per day out in the snow and wind every day, learning to track and trap animals this winter, running between traps. Now (trapping season is over for 2 months) when I eat a good sized meal after a day of work I get very noticeably warmer than before, even though it is well into spring. This article explains why. I eat a god variety of fats – free-range eggs, grass-fed free-range butter, extra-virgin coconut oil, fat from free-range animals and wild game, fish eggs and fatty fish, olive oil. Eating those types of fats may have something to do with the acumulation and activation of brown fat. My weight and body fat percentage (8-10) remained the same. This makes sense when you look at Inuit children with T-shirts on in 20 degree F weather (or colder). Their diet includes a high percentage of seal and walrus blubber, which is absolutely necessary for their survival. Surely there is some genetic adaptation involved as well.
I wonder about the fat soluble toxins of industrial society, and their effect on accumulation and activation of brown fat, and how effectively daily sauna therapy (with cold shower breaks) can detox the brown fat, as it does with white fat. It probably does a good job – the Finnish people seem to have proven that.
Now I understand why, after going primal I actually feel hotter and “emit” hot radiation! It sounded weird that while losing fat I was starting to feel hotter than before. Now it sort of makes sense. I used to justify this by saying that fat burns hotter than sugar… maybe it’s just the brown fat!
BTW: in my house in winter I have between 10 to 16 C degrees! I must be full of BAT!
Lard on!
I’m in northern Illinois and it gets quite cold here in the winter. When it gets below 30, I get super grumpy but anything above 30 feels fine. Even this last winter, walking to class everyday (20-25 mins. one way) I managed to gain weight (both muscle and fat). I’ve always joked that my Mediterranean genes (my dad’s mom is 2nd generation) demand warmer weather and I tend to maintain weight easily in the summers. Last summer, I started utilizing cold showers and my body fat dropped pretty quick and my recovery time from workouts was also improved. I’m doing the same thing again now and am noticing the same effects. Tomorrow is measurement day though – yikes!
sitting on my porch, after reading this post, the cool breeze that would normally chase me inside takes on new meaning! mark, thanks for making me smarter, tougher and healthier everyday!
Here’s my experience for what it’s worth. I grew up in Edmonton,AB (if you’ve never wintered there, look it up on a map to fully appreciate how far north it is), and was accustomed to almost always having goose bumps on my arms, indoors or out. I eventually moved to a warmer place and my cold tolerance is frequently remarked upon by people who weren’t brought up with the sort of winters I had to endure. I’m often the lightest dressed in a group. People point out my goosebumps and tell me I must be terribly uncomfortable, but it actually feels just right to me. I feel very uncomfortable on hot summer days. I’ve always been skinny.
Ooh… what can those of us with absolutely no tolerance for the cold do?
If I’m in 16 degrees C without a jumper, I’m probably shivering. Meanwhile, I’m relatively fine on a 40 degree C day.
Do we have to start much higher in order to lower our set point?
okay Canadians…16 and 40 deg. C means nothing to me (though I can’t speak for the rest of Americans) I’m feeling too lazy to go to an online converter to see what that is in F.
I’ve lived in the central african rainforest with hunter gatherers and it does get cold. At night under the forest canopy or in a storm you need a fire to keep warm. I was often wrapped in a jumper while my friends would still be in only shorts, what with not owning any jumpers. Plenty of opportunity to get cold!
I’m a swimming teacher and in the summer I have to spend 4+ hours being cold in the water (air conditioned indoor pool) a day. I find I feel more energized afterwards and I swear my metabolism speeds up. Wonder if this is the reason… interesting!
Last year I went on a retreat in which we trained ourselves to go swimming in the North Sea, which had temperatures right at the freezing point (it was February). It was amazing! I would plunge into the freezing water, and within 10-20 seconds, I felt WARM. I would then swim around a little until I started to feel cold again. Then it was time to get out. On days when I did this, I felt incredibly warm and energized for the rest of the day. I have no idea what it did for my metabolism, but it made me feel fantastic!
Boy am I now glad I joined in the Ocean plunge at PrimalCon. I just knew there had to be even more good reasons to do it.
Brown Adipose Tissue doesn’t sound very appealing… maybe we need a mascot?
I’m thinking….. BATman