Melissa Miller was never a great sleeper. Most of her life, the 41-year-old marketing director managed with just a few hours of shut-eye each night. But after 9/11, things got worse and she noticed an unfortunate change: "I started putting on weight." Twenty-five pounds, to be exact. "I didn't have the energy to exercise, and I was eating more carbs. I was craving them." She finally sought help from New York City nutritionist Oz Garcia, Ph.D. "The first thing he did," she remembers, "was stabilize my sleep."
How is this possible? Shouldn't more waking hours equal more calories burned? Actually, no. "Sleep is a very dynamic aspect of our day," says Garcia. "It isn't just a time when the system shuts down and nothing occurs. The opposite is true; a lot is occurring. The body reboots every aspect of metabolic function. The brain produces critical messenger molecules, or neuropeptides, that play a vital role in weight regulation. If you don't get seven to nine hours of sleep regularly, there appears to be a cumulative effect. After a while, those neuropeptides and beyond that, neurotransmitters can't do their job."
The science of sleep: How does it work? In her book Sleep Away the Pounds, nutritionist Cherie Calbom explains the delicate chemistry. "When you don't sleep enough, your level of ghrelin the munch hormone, which triggers appetite goes up," Calbom says. "At the same time, your level of leptin, which controls your appetite and aids in the metabolism of carbohydrates, goes down." When leptin levels drop, we crave more food, particularly carbs, whether or not we've already consumed enough calories.
What if I'm fighting my cravings and eating a low-calorie diet? Will lack of sleep still make me gain weight? Possibly. Sleep deprivation also throws other hormones key to weight management out of whack. "The whole endocrine system can get off balance," Calbom says. Unstable insulin levels can lead to increased appetite, poor sugar metabolism, hypoglycemia, and possibly type 2 diabetes. Dips in growth hormone may promote weight gain. "The adrenal glands may start pumping out cortisol at the wrong time of the day, and excess cortisol can cause fat to be deposited, especially on your midsection," Calbom continues. "I'll often hear clients say, 'I've been eating really well, but not only am I not losing weight, I'm putting on pounds.' Lack of sleep is often a culprit."