Non-shivering thermogenesis is the process by which the body generates extra heat without shivering. Shivering is a way for the body to use muscular contractions to generate heat, but non-shivering thermogenesis uses a completely different mechanism to accomplish the same goal: a specialized fat-burning tissue called brown fat. Brown fat is brown rather than white because it's packed with mitochondria, the power plants of the cell. Under cold conditions, these mitochondria are activated, using a specialized molecular mechanism called uncoupling* to generate heat.
The mechanism of brown fat activation has been worked out fairly well in rodents, which rely heavily on non-shivering thermogenesis due to their small body size. Specialized areas of the hypothalamus in the brain sense body temperature (through sensors in the brain and body), body energy status (by measuring leptin and satiety signals), stress level, and probably other factors, and integrate this information to set brown fat activity. The hypothalamus does this by acting through the sympathetic nervous system, which heavily innervates brown fat. As an aside, this process works basically the same in humans, as far as we currently know. Those who claim that rodent models are irrelevant to humans are completely full of hot air**, as the high degree of conservation of the hypothalamus over 75 million years of evolution demonstrates.
Two new studies concurrently published in the Journal of Clinical Investigation last week demonstrate what I've suspected for a long time: brown fat can be 'trained' by cold exposure to be more active, and its activation by cold can reduce body fatness.
It was previously shown that non-shivering thermogenesis is higher in winter than in summer in the same people (1), suggesting that it may be a modifiable trait. As an aside, obese people tend to have low brown fat activity (2)****. The first new study demonstrates that brown fat can be trained to be more active in as little as 10 days, and that this training causes people to become more cold-tolerant (3). The protocol involved exposing people to 60 F (15-16 C) air for two hours on day 1, four hours on day 2, and six hours on days 3-10. Although I assume they were lightly clothed, this is a pretty mild cold exposure.
The second study went further, using a longer cold exposure protocol to investigate changes in fat mass among people with low brown fat activity at baseline (4). Researchers exposed volunteers to 63 F (17 C) air for two hours a day over a six-week period; again I assume they were lightly clothed. As in the previous study, they observed an increase in brown fat activity with cold training, and they found that calorie expenditure was higher when subjects were in the 'cold' air. After six weeks of training, body fat mass had declined by about 5 percent. This is despite the fact that all subjects were lean to begin with!
I think this is pretty impressive, given how wimpy the cold exposure protocol was. Think about it: two hours a day at 63 degrees F. That would seem downright luxurious to a person 100 years ago in winter in almost any temperate climate. Today, most people keep their central heat closer to 70 F in winter, apparently eliminating a major source of passive calorie burning.
I've used heat in my bedroom about 20 times over the last three years, usually when I have a guest. I use less heat because I'm an environmentalist, and because I feel that humans are meant to experience cold stress sometimes just as we're meant to experience exercise stress. The winters aren't particularly cold in Seattle, and I leach heat from downstairs, but the temperature nevertheless fluctuates between 45 and 55 F for several months of winter, with occasional excursions below 40 F (I've awakened with a crust of ice on the inside of my windows).
This may sound extreme, but it's nothing compared to how many people in temperate climates lived in the winter before central heat. Open wood hearths are inefficient at heating a house, wood can be expensive, and the fire burns out overnight. Have you ever experienced a temperature below freezing in your home? It's difficult to stay warm without moving your body, and I must confess it's hard for me to tolerate for long, despite my relative cold hardiness. Indoor temperatures below freezing would have been common two centuries ago, as supported by many historical accounts of even the wealthy having to break ice to wash their faces in the morning.
Is the rise of central heating a contributor to the obesity epidemic? These recent studies suggest that it may be. This is consistent with what one would predict based on the evolutionary/ancestral health principle.
* As protons are pumped across the mitochondrial inner membrane as part of the normal process of ATP generation, a channel protein called UCP1 (uncoupling protein 1) diffuses the proton gradient by allowing protons to cross back passively. Since heat is nothing more than molecules moving around, this process of pumping protons back and forth generates heat. This process is called uncoupling because the Krebs cycle is uncoupled from ATP generation by the diffusion of the proton gradient.
** It is true that certain things don't carry over that well from rodents to humans, for example drug efficacy and perhaps the effects of certain diet elements on health. But basic anatomy and physiology are remarkably conserved in many areas. If you look at a rat's hypothalamus, it contains all the same structures as a human hypothalamus, though the proportions and placement are different. Same for the basal ganglia and many other major systems in the brain (the basal ganglia, remarkably, are highly conserved down to hagfish, the most primitive vertebrate). It's difficult to argue that these structures do something completely different in rodents than in humans when they look the same down to the cellular level, and we have empirically determined in many cases that they do function similarly in rodents and humans. I sometimes hear the impassioned argument "I am not a rat/mouse"! Well, actually you are. We share roughly 99% of our genes with mice, and 85% of the sequence of those genes is identical down to the nucleotide. So yes, you are a mouse, roughly speaking***.
*** OK, to be fair, small changes in the genome can have major phenotypic impacts, so percent genome identity isn't necessarily the last word. But science has abundantly demonstrated the usefulness of rodent models for understanding how humans work, and these insights are going to keep rolling in whether the skeptics like it or not. Much of this skepticism is inspired by animal rights sentiments, and/or the inherent distaste people have for being compared to an animal they consider disgusting and stupid. Although I sympathize with animal rights sentiments, and I think they should be part of the animal research discussion, they have nothing to do with the question of how useful animal research is for understanding humans. The argument from disgust is obviously irrational.
**** This could simply be because they're better insulated. Overall metabolic rate (kcals burned per unit lean mass per unit time, or total kcals burned per individual per unit time) is actually higher in the obese.
This is interesting and matches simple thermodynamics that says losing heat should make your body burn more calories to keep itself warm.
However, there is also evidence that colder body temperature lowers your metabolism.
Chemical reactions tend to be slower at lower temperatures. In order to get wood to burn and generate heat, you need to to first inject it with enough heat to bring it up to a high temperature and ignite it.
I tried both approaches on myself and keeping myself cold turns me into a computer chair potato. It makes me feel less energetic and hungrier. In the long term I think I would end up under exercising losing muscle mass and lowering my metabolism even further.
I installed a small electric heater behind my computer chair and it is now easier for me to get up and go do a workout in my exercise room even the winter. The period I need to warm up and get my energy level high enough to do a good workout is now shorter.
I wonder if taking a short (5 to 10 mins) cold showers or an ice bath would produce the same effects?
Tim Ferris suggest taking daily cold showers or ice baths will lower body fat %.
Do you think taking a 5 to 10 minute cold shower would cause the body temperature to lower enough to cause the brown fat to metabolize and produce the same effects as the study?
I can only speculate, but I think it would probably have a similar effect. A cold water shower is a shorter, much more powerful stimulus than coldish air exposure. Your body recognizes immediately that it's losing heat at a fast rate (since this is a life-threatening situation if you can't escape it), and it takes steps to mitigate temperature decline. I'm fairly confident a cold shower would strongly activate brown fat. How that would stack up to a milder, more prolonged activation, I don't know.
I totally agree that air-conditioning and heat pumps are a burden on health - and most often one that people have zero control over, in hospitals, workplaces, malls, schools.
Maintaining a lower-than ambient temperature in hot weather also costs energy. So maybe the old hot-freezing sauna cycle makes sense too.
@Benoit Essiambre:- There is evidence that a colder environment raises metabolic rate in order to maintain a constant body temperature. See Minimal changes in environmental temperature result in a significant increase in energy expenditure and changes in the hormonal homeostasis in healthy adults.
I watched a program once about a group of men who undertook a hike across arctic-like conditions - I believe it was somewhere in the Yukon Territory - and their results made me wonder if cold weather wasn't conducive to lean body mass. These men were all in very good shape to begin with, and were consuming something along the lines of 8000 kcal per day during this hike, and all still lost weight (which was not the point of the hike, just an unintended side effect). This wasn't mountain climbing either. They were just walking across flat, open land that happened to be in sub-zero weather.
I used to have below-average cold tolerance and was very prone to shivering in weather that no one else shivered in. I started using various cold-shock therapies to improve my cold tolerance to New England winters some years ago and I haven't shivered once in at least a couple years, even when taking ice cold showers, walking in subfreezing weather with no hat or gloves, etc., and the only explanation I can think of is I am now using heat from non-shivering thermogenesis instead of shivering. Wim Hoff's example inspired me to increase the difficulty of my cold training, with additional resulting improvement. I think that heat therapy can also help, which may be the other side of the hormetic cryotherapy coin. Wim seemed to confirm this when he ran a marathon in the desert without water. Eating a Paleo/ancestral-type diet also appears to help my cold/heat tolerance.
But in the winter, I keep my thermostat set at 60 during the day, and at night the furnace doesn't come on unless it gets below 50. No heat in the bedroom, and I often have ice on the inside of the window. Despite this, I have normal BMI, but I don't lose weight in the winter.
However, I do wear sweaters in the winter, and I have a down quilt on my bed, so although the rooms are cold, I'm not. As one commenter suggested, when the room is cold, it's tempting to spend the day curled up under a blanket instead of walking around, although not everyone would have that option.
When I was a preteen, my sister and I slept outside on a sleeping porch all winter, in sleeping bags. My brother did not. But we all became "chubby" at about 11 or 12.
I think cold has an effect but doesn't explain the "obesity epidemic."
On the other hand - obesity rates can be very high among people living in cold, damp houses, with poorly maintained cars (where heater/air conditioner is first to go), less likely to work in warm indoors environments.
The wealthiest, who can afford the best in ambient comfort, in food security and choice, and in labour-saving technology, tend to have the lowest obesity rates.
So these effects might be hard to pin down in any study of human populations, despite almost certainly being important.
Here's an English study linking higher ambient temps with lower BMI:
The plot thickens.
And there's this abstract:
"There was an approximately parabolic relationship between mean annual temperature and obesity, with maximum prevalence in counties with average temperatures near 18 °C [64.4 F]."
I don't have the full article, but parabolic, to me in this context, probably means the obesity incidence was highest at 64.4 F, with lower obesity incidence both above and below 64.4.
Of course, living in a particular environment doesn't equate to exposing yourself to outdoor temperatures. But it makes sense that someone living in a cold environment will have more cold exposure than someone in a hot climate.
Perhaps 64.4 F is a sweet spot for efficient body temp regulation and energy partitioning. Living at temps significantly above or below that may cost you energy-wise: you expend extra calories maintaining a normal body temperature, tending to result in lower obesity incidence.
A semantic question: regarding the first footnote, isn't this called uncoupling because it uncouples mitochondrial respiration from ATP generation? Ordinarily ATP synthase couples the proton gradient generated by respiration to ATP generation.
I have done this with both cold air and cold water, and the water is much more efficient. It took me several weeks of cold air to get to the point where I didn't just shiver, but only a few days with water. It is much harder to maintain during the summer, but I find a trip to the beach once a week, combined with low carb, works the best. I think the weight-loss part works pretty well for men.
For what it's worth, Jack Kruse is big onto Cold Thermogenesis -- http://www.jackkruse.com/cold-thermogenesis-easy-start-guide/
From Kruse's forum also comes a poster who mentions a quote from Ray Cronise, who once stated that vasoconstriction/vasodilation happens in seconds, not hours. Perhaps that implies that the cold stress response is kicked up incredibly quickly in humans?
It's probably for that reason that he recommends contrast showers, with 20 seconds cold, 10 seconds hot, and always ending on a cold cycle. Supposedly you get a very time efficient way of activating the cold stress pathways in the body.
Other incarnations of cold exposure would include putting a cool pack on your neck and shoulders (where the most BAT is usually located). It doesn't have to be ice cold, since most of the cold adaptation happens at skin temperatures of 10-13C (50-55F).
(Sidenote: Cronise and Kruse both agree that it is this skin temperature range that is the most effective for cold adaptation. ie: going lower doesn't give extra benefits)
That's the supposed mechanism of gadgets like the coolfatburner -- https://www.coolfatburner.com// . While the claims are gimicky (eat all the junk you want!), the mechanism is definitely known to be effective.
Finally, one interesting note from people who practice cold thermogenesis is that keeping the hands and feet warm, while exposing select regions (neck and shoulders) to 10C cold is actually very bearable. No idea how this works, but it seems to be consistent with the common complaint that people feel cold if their feet are cold (despite the body being warm).
The net effect of course is a high level of adherence to a cold exposure protocol. 1 to 2 hours with a cooler pack on the neck becomes very routine after a couple of tries.
On the athletic front Ben Greenfield and other athletes are big proponents of using Cold Thermogenesis for recovery. See:
For me, regular cold showers year round it is (it only gets to a low of about 3-4C here in Melbourne Australia)
Hope that provides some topics to explore.
My biochem is a bit rusty but probably the most precise way to put it would be to say that the electron transport chain is uncoupled from ATP generation.
Basically UCP1 is breaking the link between proton pumping (powered by electron transfer) and ATP synthase.
Interesting, but rather complicated. Here in all Nordic countries we have pretty harsh winters and equally good central heatings. Still, there are rather big differences in the prevalence of obesity between the countries, Norway being the least obese nation and Finland the most obese.
BTW, according to a new study in humans, exposure to cold (0 C / 32 F) may increase fat oxidation during submaximal exercise.
Further to my previous comment: Although metabolic rate increases as environment gets colder, appetite also increases (it certainly does in my n=1 case!). I tend to weigh more in the winter months than in the summer months.
I therefore suspect that food availability & marketing are bigger factors in the obesity "epidemic" than ambient temperature.
Talking about brown fat...
This study has made some headlines her in Sweden lately. Any thoughts?
Cold Exposure Promotes Atherosclerotic Plaque Growth and Instability via UCP1-Dependent Lipolysis
What I would like to know is whether browning of white fat is possible in humans. It should be, if mice really are so much like us. Imagine if all your white fat were brown! Pale brown anyway. You'd be like an Inuit baby I once saw in a film clip sitting in a snow house where the temperature can't have been much above freezing, and it was stark naked and looked pink and happy.
Here is a very interesting animal study of BAT and UCP1
"Long term highly saturated fat diet does not induce NASH in Wistar rats"
The coconut oil-fed rats maintained unchanged body mass despite consuming 143% extra calories across the board, through the magic of BAT and UCP1. The butter fed rats, same deal at only 30% extra.
As a smaller animal, the rat probably needs more BAT to maintain a stable body temperature..
The experiment shows that animals can increase BAT in response to diet.
Thank you for the great post, Dr. Guyenet.
This is very interesting but maybe not a viable solution for most obese people as most would be unwilling to give up A/C. Unfortunately, it seems that most environmental changes that can reduce obesity would be found to be too onerous by most people to be practical solutions for obesity: these would include, cold weather , high altitudes, hot weather (?), low-calorie diets, low carb diets, etc.
Given most people's inability to tolerate discomfort for long periods and the continued long-term failure of diet and lifestyle interventions, maybe the most viable solution is to have obese people pop a pill?
The anti-diabetes drug liraglutide is shown to cause weight loss and weight loss maintenance in obese people w/ and w/o T2 diabetes to such a degree that widespread drug use may significantly reduce morbidity and mortality in the population --assuming sub 10% weight loss is enough to reduce disease risk like everyone claims.
Nice article Stephan!
On the "I am not a mouse" front: due to their brown fat and body temp being a bigger part of their TDEE the changes in EE seen in various rodent studies may be larger compared to what we see in humans. They seem to have greater ability to both waste excess as heat or conserve by dialing back RMR.
Based on the observations that when people are exposed to cold air they burn more brown fat, I'd have to say that their shouldn't be any fat people in the US. This summer, I frequently have to wear a sweatshirt to work, to keep warm from the 50 deg F air that blows from building ventilation system. And people still think it's too hot!
PS Cold showers are awesomely refreshing!
I think there's a relation between temperature, activity, and food intake, so it's difficult to assess effect of temperature alone.
When it's very hot and humid (think over 95 and blazing sun, high humidity), I don't have the energy to work outside, so I stay inside, where I can keep it under 80 by closing windows in morning, and read. Also, I'm not very hungry.
When it's very cold (think below zero, maybe with wind), I can't face my usual walk, so I stay inside under a blanket and read.
With temperatures between 40 and 70, I have lots of energy and mow the lawn, cut brush, weed garden, or stack wood.
So in my case, at least, I think temperature affects activity, and this has a bigger effect on calories burned then variations in metabolic rates.
Someone who had to spend all day in front of a computer or who was forced to do manual labor regardless of temperature might have different results.
If external temps had a significant effect on obesity rates, then we'd expect populations living traditional lifestyles in cold climates (Inuit, Tibetan, northern Chinese) to be thin and those in hot climates (Amazon Indians, Australian aborigenes, southern Chinese) to be fat.
In the US, obesity rates are highest in the South. But how much of this is because of thermogenesis rates and how much because of Southern cooking and it being too hot to be outside if you can avoid it?
Is this recent mouse study something to be concerned about? http://www.cell.com/cell-metabolism/fulltext/S1550-4131(13)00247-7.
Tan Yew Wei
It looks like foot and hands are brains proxy for ambient temperature since those are parts of the body that are in contact with environment all the time.
a) I would be very interested if exposing the people that already had some brown fat activity to enough cold would produce the same results - ie how far can brown fat be activated?
b) might be a stupid question but is it true that body fat 'insulates' the body against the cold to some degree?(excuse pun). Could this be another way in which obesity seems to perpetuate itself?
"Wim produces the same amount of Brown adipose and in some cases even more than young adults. An average of 35% in comparison to the 0 to 20% of young adults, and at peaks Wim even raised over ... 50% above the normal. ... people at middle age and older are capable to activate Brown adipose after training in the cold." (The role of Brown adipose with Wim Hof, http://www.innerfire.nl/brown-adipose)
I am currently reading "The Feud," about the Hatfield-McCoy feud in the cold, mountainous regions on the border between West Virginia and Kentucky. Despite eating a diet heavy in lard and filled with corn-based menu items, the mountain men and their families were mostly slender.
In general, they lived with minimal heat at their domiciles. They generally wore light cotton clothing year round, and some of them were said to walk barefooted in the winter. I guess they must have become prime specimens of brown fat metabolism!
Great discussion everyone. Many interesting points.
Thanks, that's extremely interesting. I wonder if the authors mean activation of brown fat or conversion of white fat to brown? I can't help suspecting Wim Hof does both.
I have to ask. I was once told upon expressing my concern for my daughter's weight basically exploding at 18 months old that cold temperatures cause weight gain, particularly in children. I know babies are born with brown fat and it is very slowly replaced into adulthood, which makes this more perplexing. My experience supports what I was told and curious if you have anything to say as it pertains to babies/children.
Do you know to what extent exercise activates brown adipose tissue?
Do you know to what extent exercise activates brown adipose tissue?
Hi Stephan, again it would be limiting to view this as a cold-thing (especially a calorie-thermodynamic thing), when it's most likely more apt to discuss it as a stres-communication thing. Then you get into genetic susceptibilities of HPA, neuroendocrine measures, feedback mechanisms, socia and nutritional influence etc. Although cold temperatures (life-threat) is a novel way to motivate energy usage shifts. My feelings with reductionistic thinking is it's as effective as yanking on a single marionette string... it moves the doll, but what's necessary is a coordinated dance.
Do you think the Ray Cronise Cold Shower 20" cold, 10" hot for 5 minutes... OR Jack Kruse's 20-30 minutes Cold Submersion....OR just having a cold air or house exposure is BEST?
Also can we turn white fat into brown fat? How much?... are there certain body parts that are best to "ICE"?
So everyone that lives at the equator should be overweight of obese?
Stephan I'm sorry you live in discomfort when you don't have to, simply keep it cool!
And in the end life expectancy continues to increase, and for many reasons.
Maybe we have unrealistic expectations for life expectancy!
Excess heat also increases energy expenditure because the body has to work harder to stay cool. The temperature of minimal energy expenditure corresponds to the temperature of maximum comfort.
But there are other reasons for lower obesity rates in certain equatorial regions.
I would listen to Cronise on cold exposure before I would listen to Kruse.
Cronise is doing a ton of fascinating experiments. Kruse appears to be reading Cronise's blog and hyping up what he's read there, yet not crediting Cronise.
Surprising, I know.
@Jane I suspect the same thing. Scientists have been finding that human physiology is more malleable in more ways than previously thought, including with brown fat, as has now been verified scientifically with Wim (and scientists are planning to test Wim's students also, to see if his success is replicable).
@Cassandra Conventional wisdom makes the mistake of assuming that all human body fat is bad. Instead there is "good" body fat (such as brown fat) and bad body fat (when in excess/imbalance) just as there is "good" dietary fat and "bad" (imbalanced) dietary fat, though in both cases it's more about balance than absolute goodness/badness. Thus I suspect that a person can be "obese" and relatively healthy at the same time, at least theoretically (it's not likely to be studied anytime soon). It may be that the composition, balance, and location of body fat is more important than the total amount.
I don't see cryotherapy as a binary choice of cold = good and heat = bad so much as a certain amount of temperature stress in either or both directions is beneficial, probably largely via hormesis. Bad scenarios would include lethal extremes of super cold/hot beyond what one can endure (rare in either nature or the modern world, except for already-sickly people) or a mediocre chronic stasis of temperatures always around a comfortable level that never challenges our systems (common with modern heating, A/C and bundling up in winter clothing), killing us softly.
Scandinavian spas are famous for combining hot baths or steam or sauna rooms with cold plunges, incorporating the full range of hormetic cryotherapy. I used to wonder why their hot tubs and jacuzzis tended to be outdoors (which is energy inefficient) before I learned that they traditionally jump into snow or icy waters afterwards.
Wim Hoff found that developing world-record cold tolerance also developed world-record heat tolerance, without significant heat training and never having lived in a hot climate. So cold and hot appear to be two sides of the same coin. In cold climates it's much easier and less expensive to focus on cold therapy.
Babies are born with higher percentages of BAT, they dont shiver when they are cold, they uncouple for heat.
Cold temperatures signal the nervous system to generate heat through shivering in adults and on a more long term basis to turn up the mitochondria and initiate UCP. There are several novel compounds that do this that have an enormous shunting of calories eaten or stored burned as heat. You can die of hyperthermia using them! Cold temperatures have a similar effect as the body attempts to thermo-regulate it requires more calories to be used to maintain homeostasis. Cold temperatures raise metabolism provided that the body actually gets cold and is exposed to the cold. Wearing a space suit in your cold house wont help, you have to actually get your skin cold to initiate the process. Water speeds the loss of heat to the environment and is one of the more effective means of initiating the process. Over time your body adapts to the colder temperatures due to the mitochondrial changes and likely creation of BAT vs WAT.
lets add some physiology to the discussion. The body is in a constant state of thermo-regulation.
In colder climates, and cold exposure calories are burned to thermoregulate to a higher degree. Since water speeds the loss of heat to the environment a cold plunge will have the most dramatic effect. Simply lowering your heat and wearing more sweaters accomplishes nothing since the body's core temperature is maintained with additional clothing. Lowering your heat and being cold will unequivocally cause adaptation through uncoupling over time to therm-regulate resulting in increased metabolic consumption of calories for heat and less for storage. Over time mitochondrial adaptation occurs and the body becomes more efficient at producing heat at lower temperatures. There are chemical agents that cause uncoupling and they drive an enormous amount of stored or consumed calories to heat. In fact some are so potent you can die of hyperthermia. Interesting note, babies dont shiver, they have have BAT levels, and they uncouple for heat.
2,4 dinitrophenol was one of the first obesity drugs, used in the 1930s. It causes mitochondrial uncoupling. Quite effective but it caused deaths due to hyperthermia and was withdrawn from the market.
George Henderson cited a study, from which he summarized:
"The coconut oil-fed rats maintained unchanged body mass despite consuming 143% extra calories across the board, through the magic of BAT and UCP1. The butter fed rats, same deal at only 30% extra."
Meanwhile, Stephan posted to Twitter a link to the abstract for another study suggesting ketone esters induce the development of brown fat and improve insulin sensitivity in mice.
Are we perhaps getting slightly closer to understanding the mysterious relationship between ketogenic diets (not necessarily the "clinic" ones) and "calories in, calories out"?
"Talking about brown fat...
This study has made some headlines her in Sweden lately. Any thoughts?
Cold Exposure Promotes Atherosclerotic Plaque Growth and Instability via UCP1-Dependent Lipolysis
I'm glad that I'm not a genetic mouse knockout model (apolipoprotein E/ [ApoE/] and LDL receptor/ [Ldlr/]) ;-)
I didn't get a chance to post this here earlier, but these data are worth taking into account:
A Fat World – With a Fat Secret? | JayMan's Blog
@jack labear: is this the study you were trying to link to?
Brown fat responsible for from heart disease-related deaths in winter
[PRESS RELEASE 2 JULY 2013]
I wonder how someone with Raynaud's (like me) would respond to attempts to coax the body to burn brown fat? Someone with Raynaud's will see their fingers and toes turn bone white and become extremely cold even at temperatures in the 60's. As the extremities start to warm up, they turn cyanotic before becoming bright red and then returning to a normal pink color.
I lived in Salt Lake City for a winter without heat, average temp was about 50-55 degrees, one of the few times in my life I had a six pack....
Cold air stimulates appetite.
My high school chemistry teacher served in Korea (cold). He said that you had to eat four jumbo candy bars a day not to lose weight. A teenage girl in class asked if cold baths would help her keep slim. Maybe she hit on something.
Our KewlFit Weight Management Cooling Vests are designed to expose the body to a MILD 58°F temperature which is the same temp researchers used at Harvard Medical School. They were able to activate brown adipose tissue through nonshivering thermogenesis.
Also since our vests are not iced based they do not invoke any vasoconstriction response allowing athletes to work out in the Cooling Vest. Research shows not only increases in calories burn but also improvements in endurance and overall performance.
The following study was published in May, 2014.
Intermittent cold exposure enhances fat accumulation in mice.
Also important to note is that lean body mass also decreased as a result of cold exposure.
Both of these results were seen absent a change in caloric intake.
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