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
Makes sense to me. I tend to lose weight in winter and gain it in summer, which is the opposite of what is supposed to happen.
I live in Minnesota, and I always weigh the most in the winter. I weigh about 5-10 pounds less in the summer- my weight has been exactly the same range cycling between winter weight and summer weight for 20 years (excluding pregnancies).
I always attributed it to being slightly more active in the summer months, but now I wonder if it’s because I FREEZE all summer long in the over-air conditioned offices I work in. In the winter the offices are warmer, plus I’m wearing heavier winter clothing.
how does one gain BAT? i’d like to get some to be less cold (i’m always cold). it is not clear to me from this article.
I took a little swim in Lake Zurich, Switzerland last Monday evening, water temp about 17 C. I stepped in slowly and let everything adjust, made sure limbs in good working order and took off! It felt pretty great! It was easier to get past the adjustment stage thinking of it as an experiment in activating brown fat. Stayed in about 20 min. moving moving moving. Might try to do that once a week. For the past 6 months I have been ending a warm shower with a cold all over blast and I really believe this practice has helped fend off some of the common bugs one is exposed to, along with 80/20 primal eating habits. Still working on those last kilos, but feeling well!
Brock University In Canada has invented and researching cold suits for obesity and diabetes. There was a radio doc done on CBC about a year ago about these studies.
I have started trying to expose myself to the weather as much as possible. One it makes me feel alive. I took a hike in 50 degree rain a couple of months ago and loved it. But also I have a job where I am repeatedly exposed to the weather and if I embrace it it is a lot easier. When cold weather came last fall I made it a point to acclimate and it made a huge difference. Its amazing what your body will do when you apply the right stress.
I live in Chicago which can be very cold. I am a winter/snow enthusiast and plein air painter. I paint outdoors even in winter – standing for hours.
I am a weightlifter and primal eater.
I have experienced thermogenesis “sometimes” after being out painting (and properly insulated). 3 hour naked bikeride on a 62 degree evening only made me cold and shiver for a week afterwards.
Women supposedly have more BAT. Perhaps it activates differently than men. And hormones seem to be the name of the game here… different for men/women
If BAT is being activated I cannot consistently produce a thermogenic event. I’d love it to be true but for now I think it’s still in the theory stage (Yes, I’ve read Dr. Jack Kruse’s stuff). Chicks are different yo!
Pasture raised hamster eh? Hmm….my house is currently being invaded by chipmunks (free range!). I wonder how they would go with a side of asparagus…
I have been doing vasper http://www.vasper.com for a month. one exercises on a recumbent bike with COOLED compression cuffs around thighs, arms, core. The thoroughly researched effect is to raise lactic acid and consequently growth hormone. Results? deep sleep, weight loss, muscle development, increased immune function, a pronounce reduction in hot flashes. that is for normal folks. people with diabetes and thyroid dysfunction as well as spinal cord injury patients, auto-immune patients (RA, MS, DM) all see huge gains in performance. This, folks, is NOT bullshit. Just follow Peter Wasawoski’s 30 years of research for NASA…..
Hi Everyone… I have news for you…Air conditioning and cold temperatures add to body fat and more yes more adipose tissue. There have been several articles (“Outside” magazine, Atlanta Journal last summer on that very subject. I can attest to the opinion of more cold = more fat and slugishness. Am I a heat-loving lizard? Probably, thank you very much !
Where’s the darn Like button?
This is great news for me as the AC has been turned on in my office building and it’s so cold in here I’m in a consistent state of goosebumps! YAY cold!
Is it the chicken or the egg?
Hot people are more likely to seek cold and cold people the heat. Are people spontaneously bundling up MORE and exposing themselves to the cold less? Or have they poisoned their metabolisms with bad foods? I’ve found that a good marker of a healthy metabolism is increased resistance to cold.
With that said, it sounds refreshing to go on an Alaskan retreat with a big stock of salmon and firewood in a grizzly-monster-proof cabin. Mmm salmon. Stars, snow, beautiful mountains…the smell of fresh pine.
It’s now officially summer here in WA and I just bought a contoured icepack for the neck. I plan to combine with a broad, rectangular ice pack pinned to my shirt for some ‘brown fat training’.
So I’ll ice the neck, throat, upper back and chest area during the summer when it’s more tolerable) where brown fat is purportedly more concentrated, with hopes of switching on that brown fat in time for winter.
When considering the options of cold showers of any duration, cold plunges or using ice packs, I realized I would only realistically use ice packs. I can’t even will my hand to turn the shower dial to cold! But, I’ve recently iced the heck out of my lowback/sacroiliac area so I think I can deal with icing higher up. Wish me luck!
I’m in a PT situation over the last 5 months that has prevented me from anything but the lightest “exercise”. I’ve been Primal/Paleo for 3 months and it’s time to step up my game.