Last year, researchers at the University of Chicago discovered that men who slept four hours a night for nearly a week had 20 percent lower prebreakfast levels of leptin–the hormone that makes you feel full–than when they had slept a solid nine hours a night. In a related study, sleep-deprived men exhibited increased appetite, especially for high-calorie carbohydrate foods. Then, in a study published last April, researchers at Yale University made a connection between insomnia and obesity: In response to stress, they found, certain neurons in the hypothalamus, which regulates both appetite and wakefulness, not only were unable to filter signals (leading to insomnia) but also reorganize and get overstimulated (leading to overeating).

"Often, when people are exhausted, they tend to overeat as a wake to stay awake," Young points out. "The best thing to do is eat foods containing protein and fiber, as they prevent flucuations in blood sugar."