the risk of sleep-disordered breathing increases due to compromised respiratory function," say Margaret Moline, PhD, and Lauren Broch, PhD, two sleep specialists at New York Weill Cornell Medical Center.
"If a person is overweight and suffering from sleep-disordered breathing, he/she may not be as motivated to exercise or to diet. When apnea leads to daytime sleepiness, it may be that much harder to begin or sustain an exercise program, which has been shown to help people begin or maintain weight loss." Not only does obesity contribute to sleep problems such as sleep apnea, but sleep problems can also contribute to obesity. A 1999 study by scientists at the University of Chicago found that building up a sleep debt over a matter of days can impair metabolism and disrupt hormone levels. After restricting 11 healthy young adults to four hours' sleep for six nights, researchers found their ability to process glucose (sugar) in the blood had declined—in some cases to the level of diabetics.
A follow-up study tested healthy men and women with an average body mass index; half were normal sleepers, the other half averaged 6 1/2 hours or less. Glucose tolerance tests showed that the short sleepers were experiencing hormonal changes that could affect their future body weight and impair their long-term health. To keep their blood sugar levels normal, the short sleepers needed to make 30% more insulin than the normal sleepers. Both studies were led by Eve Van Cauter, PhD, who termed sleep deprivation "the royal route to obesity. Despite not yet being overweight," she said, "these young adults had profiles that predisposed them to putting on weight."
"Dr. Van Cauter's research shows that people who don't sleep adequately have physiologic abnormalities that may increase appetite and calorie intake," notes Simon. "The level of leptin [an appetite stimulating hormone] falls in subjects who are sleep deprived, which promotes appetite. It suggests that at least one factor in obesity can be sleep deprivation. Poor sleep and sleep deprivation may increase appetite. Because the psychological manifestations of fatigue, sleep and hunger are similar, as adults, we sometimes confuse them—we