3. The fat-burning effect is lasting.
Spending time in cold weather spurs your body to produce brown fat, a type of soft tissue that’s loaded with calorie-hungry mitochondria. So the more time you spend outside in winter, the more brown fat (thus, mitochondria) you’ll develop. To prove it, researchers from the National Institutes of Health (NIH) asked a small group of subjects to switch from sleeping in 75-degree temperatures to a nippy 68 degrees. Over the next month, they experienced a 42 percent increase in brown fat. Plus, in a second NIH study, researchers found that cooler temps increase your body’s production of irisin, a hormone typically secreted during exercise to facilitate calorie burn.