As I sit freezing half to death in the draft of an airconditioner, I recalled having read that cold temperatures promote fat loss. Example
How does cold interact with fat loss? What’s the role of brown fat? Can I get brown fat instead of regular fat if I spend a day in 20(C) temperatures? How long does brown fat ‘last’? What’s the straight dope?
A pretty good review of the potential (limited) role of brown fat.
Highlights-
The rooms were indeed cold enough to be uncomfortable for the two hours and unlike the claim made in WP article, it may be unlikely that not being comfortably cool would do it: the brain has to perceive a thermal threat.
Brown fat won’t help unless you use it. You’ve got to keep exposing yourself to some degree of cold stress to activate it.
OR, as one of the studies suggests, there may be drugs that can activate as well.
The other side of the discussion is that while those baseline lean Japanese subjects did lose a modest amount of fat mass there may be in broader populations compensatory mechanisms on appetite. I’d strongly suspect that in a large number of people intermittent cold exposure at rest triggers more eating which more than offsets the additional calories burned by brown adipose tissue in non-shivering thermogenesis.
Probably not, as that’s a completely normal room temperature. How toasty do you keep things normally?
What follows doesn’t apply when you’re exercising or similarly active, because then you’re generating more heat than you need anyway.
But if you’re sitting on the couch or some such, your body needs to burn calories to keep your body temperature at 37 degrees. If you’re exposed to the cold this takes more energy than if you’re in a warm environment.
Brown fat can directly turn fat into heat. However, adults don’t really need brown fat because they have big muscles that can contract and generate heat.
My personal experience: there does seem to be some correlation between sleeping under cooler covers and more weight loss, but it’s hard to say whether that’s a coincidence or if it really makes a difference. I did find out that when it gets sufficiently cool in my bed (but not so cold it really bothers me) I have a hard time falling asleep.
Thanks. I’m still a little confused as to the mechanism of the fat loss. What is happening to overall body composition when you gain brown fat(ceteris paribus)? Do you lose normal fat in other areas? Then when you expose yourself to cold, does the brown fat burn itself to release heat, thereby leaving you with less overall body fat?
Maybe it’s because I’m in the draught, but the 20 degree temperature on the AC is feeling quite uncomfortable.
My understanding (I am by no means an expert on this) is that the brown fat you have is activated. Activated brown fat sucks up glucose and uses it in mitochondria producing heat, at least that is what that measure as its activity. Maybe it can suck up free fatty acids too - I don’t know. In the human studies at least the subjects did not make more brown fat; they made what they had become more active in response to cold threats - hence there was less shivering. In these human studies they did not see increases in brown fat mass or white fat becoming brown fat like (“beiging”).
The loss of normal (or white) fat was statistically significant but small. They lost 0.7 kg on average, that’s about a pound and a half. Of course these were lean Japanese subjects (average BMI 22 at the start) but even if the same percent of body fat was lost, 5% of body fat, (something we have NO IDEA about whether or not it is true) a morbidly obese individual would still only lose a fairly small amount of fat. 100 pounds of fat would mean 5 pounds of fat loss. Not insignificant but not some dramatic change either. They do seem to lose it more from the white fat though and leave the brown fat alone.
A side note: the air from your ac is probably quite a bit cooler than the temp set on the thermostat. The cold air from the ac mixes with the (presumably) warmer air in the room resulting an overall temp of 20c (or whatever you set the thermostat to).
You’re probably right. I was thinking only of the windchill effect, but just the temperature of that draught is also probably lower.
The other bit, if I understand it right, is that the actual temperature matters less than the fact that your brain perceives it as uncomfortably cool, that is as “a perceived thermal threat.”
To clarify some details from the human studies -
The Dutch one kept a total of 17 male and female lean young adults (average age 23 years old, average BMI 21.6) in a cool (15 to 16 degrees Celsius which is about 60 degrees Fahrenheit) for 6 hours a day for 10 days and documented activation of brown adipose tissue and cold acclimation during that time. They found no gender related differences. They noted that “no significant changes in body weight and body composition were observed, which may indicate that increased energy expenditure was compensated by increased food intake or reduced physical activity. Alternatively, for measurable changes in body composition, a longer cold acclimation period may be needed …”
The part of the Japanese one relevant to the circumstance at hand, chronic daily exposure, looked at 22 of the 51 lean young adult males (average age 24.4, average BMI 22) initially studied to measure acute effects. These 22 had little or no brown fat activation in response to cold stress at baseline. They used 10 as a control group and 12 they subjected to 17 degrees Celsius (62.8 Fahrenheit) for 2 hours a day for 6 weeks. At the end of the 6 weeks there was no significant difference in weight between the two groups but the difference in fat mass reached significance. It was a loss of about 1 1/2 pounds, about 5% of the fairly slight fat mass these lean individuals had. They do not state what time of year the study was done in.
Further clarification: brown fat is actually of muscle origin embryologically and in youth at least stores only a modest amount of fat - more of its cell volume is filled with mitochondria (which is why it is brown and not fat). Aging and overeating however causes it to store more fat and lose mitochondria, i.e. to “whiten”, in mouse models at least. Not sure what is chicken and what is egg here … the implication in some of what is being written is that having more brown fat, or at least more activated brown fat, might be significantly protective against obesity, but it seems as likely that the same behaviors that cause white fat gain are just also causing brown fat to whiten, that the relative lack of brown fat may be a proxy for at risk behaviors rather than a significant contributor to fat gain or loss.
Again, it is also not at all established that what was found in these two smallish studies of lean young adults would hold in young overweight or obese adults, or middle aged or older adults, let alone or adults who were both. Minimally I’d suspect the same temperature functions as less of a thermal threat as fat is insulating and the peripheral vasoconstriction of that layer is fairly effective at protecting core temperature.
I remember vaguely… I think *some * people have brown fat? And it needs to be induced to grow by cold temperatures, I think. Whether the white fat cells turn into brown fat cells, or the brown fat cells already exist and then “turn on”,… I feel like I remember one the study’s saying it’s the former. Of course, as mentioned above when a person is exposed to lots of cold.
And then they suggested that what they could do for weight loss is use stem cells to turn a lot of your fat cells into brown fat cells, and then inject them into your adipose tissue, which would stimulate the conversion into brown fat cells, which would then burn up the white fat around it. Though of course you would be warmer as this is happening 
You know what’s an easy weight loss? Thee was some kind of ultrasonic fat melter that was only approved in Canada, I dunno if it got approved in the US yet. And it wasn’t a BS one, like it really worked. People lost like 15 lbs. I can never seem to find the video on youtube though
If we’re talking about alternative ways to remove fat, what about some form of dialysis? Simply remove fatty acids directly from the blood. Of course this only works if the fat cells then start giving up fat to the blood. If they do, this could be very effective.
So in conjunction with your earlier post(where you noted that the mechanism is activation of brown fat), does this mean you can lose brown fat, but cannot gain it?
My body fat is somewhere between 16% to 22%, depending on how it’s measured, and I’m 30, so at least for my purposes, these studies should hold. But it is an important point for general consumption, so I see why you’re making it.
Well its clear that exposure to cold MUST make you lose weight.
Your body does stay at body temp,and heat lost rate (power) is related to the DIFFERENCE in temperature… so when its cold you lose heat…
If you don’t get hypothermia then your body must have oxidized food (ATP,glucose, fat) to make that much heat.
I suspect the report is XKCDian… “There’s a correlation between weight loss and having blue M&M’s as ones favourite MM’s.”… Or some other silly correlation.
In this case, as people lose weight, their fat cells turn brown… But the headline suggests that brown fat helps one lose weight… what , get a transplant ? grow it in a test tube ?
I’ve seen papers that discuss exactly that possibility. You can take adult stem cells from a patient and treat them with the right mix of growth factors to differentiate them into brown fat cells. Then you could simply inject them back into the patient.
Alternatively, in mice at least there are several ways to stimulate the growth and differentiation of new brown fat cells, or activate existing brown fat. The same growth factors that induce differentiation of stem cells in a dish (e.g. BMP7) also work when injected or otherwise upregulated in animal models. It may also be possible to activate the differentiation pathways with pharmaceuticals.
Not quite. Just that we don’t yet have much evidence in humans that we can. But the human studies are pretty limited. It does seem clear that we can at least prevent loss and make what we’ve got become much more active.
As was explored in one of the linked articles as a possibility. Thing is the effect is pretty damn modest.