THE DETAILS: In an article published in this month's issue of Strength and Conditioning Journal, Schoenfeld analyzed the research that's been conducted on how our bodies function during exercise and concluded that, whether you eat or don't eat before exercise, research shows your body burns the same amount of fat. And working out on an empty stomach can actually cause muscle loss, he adds, if you do it on a regular basis. When you're hungry, your body goes into survival mode and draws protein away from muscle, where it's less crucial to survival, than from your kidneys and liver, where the body normally looks for protein. "Your body cares more about survival than looking good at the beach," he says. As a result, you lose muscle mass, which can, over time, suppress your metabolism and make it harder to lose weight.
On a more basic level, he says, exercising on an empty stomach means you don't have the energy to put in a really good workout. "One of the benefits of aerobic exercise is doing it at a higher intensity," he says. "If you're just getting out of bed, slogging through your exercises like a zombie, you won't be able to get that intensity."
