The less you sleep, the more you may weigh. Stanford University School of Medicine researchers found that regular sleep loss is linked to elevated amounts of ghrelin, a hormone that triggers appetite, and reduced leptin, a hormone that tells your body when it’s full (Public Library of Science, 2004, vol. 1, no. 3). The study showed that five hours of sleep—well below the recommended standard of eight hours—is associated with a higher body mass index. “There is the increasing suggestion that sleeping too few hours predisposes you to obesity and other health complications,” says Emmanuel Mignot, MD, PhD, study coauthor. “Recovering healthy sleep may be a way to control body weight.”