Chill Out

Fitness classes may be turning up the heat, but the latest research says goose bumps should be en vogue.


Illustration by Sam Island

Bikram yogis sweat it out in 105-degree heat. Hot barre enthusiasts bump the thermostat up to 92 degrees. But the new trend in fitness may be more about keeping your cool.

It turns out that exercising in cooler temperatures can stimulate the production of calorie-burning brown fat—a substance found on the neck, chest, and around the collarbones that keeps the body warm by converting calories into heat, unlike white fat, which warms us by insulating. To promote brown-fat creation, George King, director of research at Joslin Diabetes Center, designed what he calls the “Joslin Coolout.” His 45-minute program involves splitting time between cardio and strength training every other day in a 62- to 64-degree room, wearing lighter clothes that allow you to stay slightly chilled.

Because brown fat burns sugars, replacing white fat with brown could have lasting benefits for patients with type 2 diabetes as well, King says. In other words: It’s time to cool down.