In times of stress, our bodies release cortisol, Dr. Charlie Seltzer, a physician board-certified in obesity medicine, told POPSUGAR. Cortisol is also known by its alter ego: the stress hormone. "By itself, cortisol does not cause weight gain," he explained. "It is a catabolic hormone that causes weight loss by breaking down muscle and fat." But that, unfortunately, doesn't mean that more stress equals weight loss. Cortisol is actually an appetite stimulant, Dr. Seltzer said, which explains why when you're stressed, you want to eat. And you can have a harder time saying no to carb-y, fatty junk foods.