Above: Image © istockphoto.com/mandygodbehear

“Put on a jacket, it’s chilly outside!” Sometimes I’d pretend I didn’t hear my mother since I didn’t think I looked cool in a jacket. I did start to feel cold without one, but is feeling cold really so bad for you? Recent studies suggest that it probably isn’t. In fact, cold may even have benefits. Let me explain.

Did you know? Homeostasis refers to processes occurring in the body that keep its internal conditions, including temperature, stable.

Your body needs to keep its inner temperature constant. When it begins to get cold, it does this in two ways: by saving and generating heat. To save heat, your body redirects blood flow deeper inside itself and away from the skin. It also forms goose bumps for insulation. One way your body generates heat is by shivering. But heat can also be produced by burning fat, which is where the benefits of cold come into play.

Brown and white fat

Your body can only burn the fat from brown fat tissue to generate heat. And unless you’re a baby, you don’t have very much brown fat tissue. (Babies can’t shiver so they need another way to generate heat.) As you grow up and your muscles learn to shiver, you lose most of your brown fat. Adults are left with only white fat tissue, where fat can be stored but not burned.

Did you know? Our ancestors experienced “metabolic winter” through prolonged exposure to cold, nutrient restriction, and long nights of sleep.

Differences between the two types of fat tissue are striking. Cells in white tissue are loaded with fat but not much else. To maximize the amount of energy it holds, each cell is like a sac filled to the brim with a single glob of fat. And because the cell is not equipped to extract energy out of it, the fat just sits there.

Cells in the brown fat tissue, on the other hand, contain many mitochondria. These organelles, which are brown, extract energy from the fat and convert it to heat—a process called thermogenesis. And since it must fuel the mitochondria, the fat is dispersed throughout the cell in small drops. In a way, brown fat tissue works like a stove that is actively burning wood, while white fat tissue is like the woodshed.

The question is, how come your internal woodstove shuts down as you grow up? Wouldn’t it be better if you continued to carry brown fat tissue? Actually, it would. And there are ways to grow some brown fat tissue.

Metabolic winter and firing up your metabolism

According to the metabolic winter hypothesis, people lose brown fat because they don’t use it. Metabolic winter refers to how the human body evolved to fire up its metabolism and generate its own heat when the weather got cold.

Did you know? Present-day nutrient-rich diets, along with chronic sleep deprivation, may compound the negative effects of excess warmth, such as obesity and type-2 diabetes.

But these days people rarely experience prolonged cold. It still gets cold outside, but your body doesn’t need to fire up its metabolism because you have warm clothing and there is usually a heated building or vehicle nearby. And because people now enjoy warmth year-round, brown fat tissue has become obsolete.

As your internal stove falls into disuse, you lose the ability to burn up fat and all your fat tissue becomes metabolically inactive and turns into white fat deposits. This has negative effects on your health. For example, research has linked the absence of brown fat to susceptibility to a variety of medical conditions, such as obesity, type-2 diabetes, and cardiovascular disease. This is because, along with the brown fat, the body loses a method of removing the excess of fat and sugar from the bloodstream.

But here is the good news: your stove can be restarted! You can gradually grow and activate your brown fat tissue through regular exposure to mild cold, such as keeping the room temperature at 16-18°C or regularly swimming in cool water.

Some people even opt for extreme cold therapy, which can involve wearing ice vests, avoiding warm clothing in winter, and immersing themselves in icy water. But these activities involve serious risks, including frostbite and hypothermia.

* * *

Along with exercise and a proper diet, exposure to moderate cold is actually good for you. By firing up your brown fat, it increases your chances of staying lean and healthy. So turn down the heat and chill—it’s good for you!

Learn more!

The ‘‘Metabolic Winter’’ Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease (2014)

R. J. Cronise, D. A. Sinclair & A. A. Bremer, Metabolic Syndrome and Related Disorders 12

Scientific article discussing the implications of changes in lifestyle for how caloric consumption is traditionally measured, as well as the relationship between caloric scarcity, mild cold stress, and sleep.

The Benefits of Being Cold (2015)

James Hamblin, The Atlantic

Supercharging Brown Fat to Battle Obesity (2014)

Melinda Wenner Moyer, Scientific American

Magazine articles discussing brown fat and the benefits of cold.

Magdalena Pop

Magda Popp

I am a biochemist and educator working to increase students’ motivation for learning science. I earned my PhD at the Max Planck Institute for Biophysical Chemistry in Göttingen (Germany), where I did research on human viral infections, primarily HIV/AIDS. In 2001 I started teaching high-school science in Canada, and in 2013 I became a mentor for Alberta's high school teams participating in the international Genetically Engineered Machines (iGEM) competition. Writing articles for CurioCity is one of the ways in which I follow my passion for sparking genuine excitement and curiosity about science. Check out my blog - School Sense - here.

En tant que biochimiste et éducatrice, je travaille afin de susciter l’intérêt des élèves pour les sciences. J’ai obtenu mon doctorat de l’Institut Max Planck de chimie biophysique à Göttingen, en Allemagne. C’est là que j’ai fait des recherches sur les infections virales humaines, principalement le VIH/SIDA. En 2001, j’ai commencé à enseigner les sciences aux élèves du secondaire au Canada. En 2013, j’ai été un mentor pour les équipes albertaines participant à l’iGEM, une compétition internationale de machines génétiquement modifiées. La rédaction d’articles pour CurioCité est une des façons dont j’essaie de susciter un véritable enthousiasme pour les sciences. On peut visiter mon blogue, « School Sense », en cliquant ici.

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