If cooler weather is your cue to hunker down in the gym, it may be time to rethink that strategy. The reason: Some studies show that you may actually burn more calories when you break a sweat in the cold. There’s even a new boutique fitness spot capitalizing on this idea. At Brrrn studio in New York, the climate is kept between 45°F and 60°F. But does the science on this stuff actually pan out? We got experts to weigh in, plus offer pointers on getting it done.