Cold climate calorie burn

A That's Fit reader asked if exercising in cold weather burns more calories than the same workout in a hot climate. After looking into it, the answer is not simple. Here are a few facts on cold weather exercise provided Nancy Clark, MS, RD, a renowned nutrition counselor:

• Interestingly, cold weather itself does not increase calorie needs. You do use a significant amount of the heat generated by cold weather exercise to warm and humidify the cold air you breathe in, which means you don't need to sweat as much as you would in the summer. For example, of the 600 calories burned during an hour of cross-country skiing in zero degree weather, about 23 percent of the calories are utilized to warm the air.
• If you get cold enough and start to shiver, you'll definitely burn more calories -- up to 400 an hour. Shivering is an involuntary tensing of the muscles to heat and warm the body.
• Wearing heavy clothing will burn more calories -- the Army rations 10 percent more calories for troops sporting cold weather gear. But jogging in the winter with a couple layers on is not comparative to a soldier marching with winter gear and a heavy pack.
• If you're cold while exercising you will burn more calories to keep your body warm. One study showed scantily clad subjects exercising in the cold burned 13 percent more calories than when performing the same activity at room temperature. But it'd be silly to freeze your butt off running in shorts on a 20 degree day simply for a better calorie burn.

In the end, the average winter workout will not necessarily burn a ton more calories than a summer one. But it's all a matter of degree -- if you're high altitude mountaineering clad with layers of clothing, boots, climbing gear and start to shiver, you'll likely set a new personal record for calories burned. Thanks to Bill for the great question.