The study, published in the journal Cell Metabolism, adds to a growing body of evidence showing that our increasingly comfortable indoor environments and well-insulating clothes protect our bodies from the need to shiver—and that's not a good thing. Shivering, this new study found, activates an endocrine hormone called irisin, that can kick start the production of brown fat, and 50 grams (about 1.5 ounces) of brown fat can burn 300 calories.
Irisin is produced by your muscles when you exercise and helps convert white fat into brown fat, but the study's authors found that after 10 to 15 minutes of shivering, a small sample of seven healthy adults produced as much irisin as they did during an hour of moderate exercise.
So is the solution to obesity to exercise less and shiver more? The best answer could be to do more of both—and to train yourself to be comfortable at cooler temperatures, according to another paper published in January's issue of Trends in Endocrinology and Metabolism. The authors of that paper suggest that such "temperature training" could help you lose weight and boost your heart health (not to mention the benefits to your energy bill and to the planet from the reduction of all those fossil fuels you won't need to burn to stay warm). They write that spending two hours a day in the range of 62 to 66 degrees F boosts brown-fat production, although how much is difficult to say, considering that people's tolerance of cooler temperatures varies. But in addition to contributing to weight loss, they add that keeping yourself slightly chilly keeps your cardiovascular system moving, which can prevent blood pressure problems later in life.
The bottom line? Turning down your thermostat and wearing a few less layers when you're outside in winter (within reason) could pay off in a flatter belly and a healthier heart.
For more ways you can activate brown fat, check out these 3 Crazy Ways to Burn Fat.