Could exercising in frigid temperatures make us healthier?

Many of the purported benefits of cold hinge on brown fat, sometimes referred to as “good” fat. Long known to exist in human infants, brown fat burns calories and generates heat.

Dr. C. Ronald Kahn, a researcher at the Joslin Diabetes Center at Harvard Medical School, was among the first scientists to document the existence of brown fat in very small amounts in adults in the mid-2000s.

People can increase their levels of brown fat by being in mildly cold environments, Kahn says, though the effect on the number of calories they burn will be relatively small.

“The average person will burn an extra 100 to 200 calories a day when brown fat is activated,” Kahn says. “But if you go eat half a muffin, forget it.”