Gut Check is a periodic look at health claims. We ask: Should you believe this?

The claim:

E

xercising in the cold burns more calories than exercising in warmer temperatures, making it easier to lose weight. Specifically, people who hiked in temperatures ranging from 15 to 23 degrees burned 34 percent more calories than people who hiked in temperatures in the mid-50s, according to a recent study of 53 men and women who took part in a vigorous National Outdoor Leadership School program in Wyoming.

Tell me more:

“Cold is much more metabolically expensive,” said Cara Ocobock, of the University at Albany, who did the Wyoming study. “You have to burn more calories” through what’s called thermogenesis just to keep the body warm. (Hint to dieters: bundle up less; you’ll burn more calories than if you’re engulfed in goose down and wool.)

The men in the outdoor school burned an average of 3,822 calories per day while hiking in the mountains during the spring and 4,787 calories per day in winter; for women it was 3,081 in spring and 3,880 in winter, Ocobock found. This was the first study to measure how calorie expenditures varied by ambient temperature in the real world rather than an exercise lab.

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Although exercise alone is an almost impossible way to lose weight (because people often eat more after working out, more than compensating for the calories burned), many of the outdoor school participants did shed pounds. In cold weather they burned 2,000 more calories per day than they consumed, on average, compared to 1,000 calories in warm weather, leading to weight loss (more in women than men).

Really?

While such results might seem like an invitation to be a couch potato in warm weather and schedule a year’s worth of outdoor exercise for winter (more bang for the buck), naturally things are more complicated. “There is a trade-off,” Ocobock said. “You generate heat through movement.”

Since movement — a brisk walk in sub-zero temps, say — warms you somewhat, you don’t need to burn as much fat to achieve the same body-warming result. That raises the possibility that you might maximize calories burned by minimizing movement in the cold — say, by taking a slow stroll so your muscles generate less heat, leaving more for your calorie-burning metabolism to do — and then doing your workouts at a nice toasty gym.

Exercise physiologists don’t know whether that’s so, Ocobock said, but research does show that it’s possible to leverage cold temps to burn calories with essentially no effort. Sleeping in a cold room, for instance, raises the basal metabolism rate, making you burn more calories doing “nothing” (other than breathing and keeping your organs functioning) than you would in a warmer room. That avoids one of the downsides of cold-weather exercise — namely, that it may make you hungrier than exercising in warmer conditions.

In general, chilly (but well above freezing) temps increase thermogenesis by up to 30 percent, a 2014 paper found, while temps cold enough to make you shiver can generate more “brown fat,” which is particularly good at thermogenesis and therefore burning calories.

The verdict:

Lots of factors influence how many calories you burn but, in general, heading outdoors in winter for some brisk activity is a two-fer.

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  • Please include Dr Ocobock’s professional title, it isn’t clear what position she has with Albany in you’re article without googling her name. Also, it’s safe to assume she worked very hard to achieve that PhD and some recognition of that’s fact is warranted when citing her work for you’re article.

  • Thank you for answering this question! Many of us in New England began our annual training for the Boston Marathon last weekend (cold!), and it reminded me that the main use of calories in the cold weather seems to be warming the air we take in! Also, when it’s so cold, it’s hard to drink as much water as you need, but if you’re metabolizing more quickly, you probably need even more fluids than in warm weather, right? Thanks for the insights!

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