Have you gained a few pounds this winter? Many of us have, thanks to the Arctic vortex or latest snowstorm keeping us indoors. In fact, Brazilian researchers found last year that levels of “bad” LDL cholesterol rise by 8 percent in the winter compared with the summer — likely because we eat fattier foods and exercise less when the chill sets in.
“My car thermostat tells me it’s 16 degrees Fahrenheit,” said Harvard Medical School cell biologist Bruce Spiegelman as he drove to his lab at Dana-Farber Cancer Institute last Tuesday morning. “Who wants to go for a nice brisk walk in weather like this?”
But Spiegelman’s recent research suggests that a brisk walk in the cold air is the perfect thing to do in order to activate a certain type of fat in your body — called beige fat — that boosts the calories you burn by up to 30 percent to generate additional body heat.
“Being cold definitely increases the activity of beige fat to boost energy expenditure,” Spiegelman said. In the winter, though, we tend to seek out warmth at all times. We bundle up in a heavy coat and hat when we head outdoors, and we turn up the temperature on the thermostat at home.
“The key is to feel a little cool, but not so cold that you’re very uncomfortable” to the point of shivering, Spiegelman added. He sets his thermostat to 68 or 69 degrees, much to his wife’s chagrin. “I think it likely burns more calories than if I had it set to 71, but if I turned it down to 65, I would need extra sweaters and gloves, so that would defeat the purpose.”
Spiegelman and his colleagues also found in researching mice that those exposed to extreme cold eat more calories to warm up whereas they didn’t eat more when exposed to moderately cooler temperatures. “This needs to be verified in human studies,” he added.
Some researchers have begun to study the effects of cold exposure in humans. A recent study from Japan found that volunteers who spent two hours a day in 63-degree temperatures for six weeks experienced a significant decrease in body fat. A group of Danish researchers reported that people who spend six hours a day at cooler temperatures wind up adjusting after 10 days — shivering less and feeling more comfortable in the cold. In a commentary published last week in the journal Trends in Endocrinology & Metabolism, researchers advocated for “temperature training” during the winter months similar to exercise training.
“What would it mean if we let our bodies work again to control body temperature?” Wouter van Marken Lichtenbelt of Maastricht University Medical Center, the lead author of the paper, said in a statement. We would be likely to experience an increase in metabolism that could be enough to prevent winter weight gain, he theorized, but that needs to be confirmed in future research.
Dr. Caroline Apovian, director of the nutrition and weight management center at Boston Medical Center, agreed that our reluctance to feel chilly while sitting indoors during the winter months could be a contributing factor in the obesity epidemic. The same, though, could be said for our reliance on air conditioning during the summer months.
“Your body needs to burn calories to dissipate warmth to cool you down or to generate heat when you’re cold,” she explained. It’s when you’re in a Goldilocks climate — not too hot, not too cold — that your body requires the fewest calories to maintain your body temperature.
For those like myself who have a hard time adjusting to colder temperatures — my fingers turn white and my feet get numb when my thermostat dips below 70 degrees — Spiegelman proposed another solution during the winter months.
“Endurance exercise, like running on a treadmill, is another great way to activate beige fat,” he said. If I could grit my teeth and head out for a run in the frozen outdoors, so much the better, he added.
Exercising outdoors in these temperatures, though, requires extra precautions to protect against frostbite and hypothermia. Those who head outside for a workout should dress in water-proof layers that wick away sweat, and cover their mouths with a neck gaiter to protect their lungs from the dry arctic air.