Baby, it’s cold outside. For most of us, cooler temperatures mean reaching for cozy sweaters and cranking up the heat. But rethinking that last part can be wise for those looking to lose weight.
The line of logic is pretty simple: When you’re cold, your body has to work harder to keep you warm, and the harder your body is working, the more calories you burn. But is that actually legit? According to the experts, yes — and there’s even some serious science behind the fat-burning process.
The secret lies in the fact that not all fat is created equal. We each have two types: white fat and brown fat. “Simply put, the main function of brown fat is to generate body heat,” says Niket Sonpal, MD, assistant clinical professor at Touro College of Osteopathic Medicine in New York City. “Meanwhile, white fat is basically just a storage form for calories.”
When it comes to your waistline, this means that engaging brown fat is a really good thing — as it fires up to keep you warm, it starts torching calories, too. The bottom line is when you’re cold, you burn more brown fat and therefore more calories.
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But the benefits of turning down the thermostat don’t stop there. Research has even shown that keeping your body a little cooler can actually help you to produce more brown fat — the more brown fat you have, the greater your calorie-burning resources. In a recent study from Australia, researchers looked at the body-fat composition of participants over a four-month period. During the first month, the participants slept in a regular-temperature room (about 75°F, in which your body doesn’t have to work to keep warm). In the second month, the researchers lowered evening temperatures to about 66°F. In the third month, they turned it back up to 75, and in the final month, they cranked up the heat to about 80.
Turns out, the calorie-burning brown fat increased by up to 40% during the chilly month, and the hotter it got, the less brown fat the researchers found in the participants. In other words, keeping things cool really can help you watch your weight.
According to Sonpal, the extra calories can add up quickly — we’re talking between 100–300 extra calories burned per day. “If you turn the temp down to near freezing that’s obviously not safe,” he says. “But especially if you’re going to work out in the winter, being in cooler temperatures will help you burn more calories.”
In short, keep the thermostat around 65°F and you’ll reap the brown fat benefits. Pretty cool.