Lose weight while you sleep? It sounds too good to be true—but recent research indicates that there is a connection between how much you weigh and the amount of shut-eye you get per night.

Two hormones, ghrelin and leptin, help to control appetite. When you do not get enough rest, levels of ghrelin, which increases hunger, rise; levels of leptin, which promotes feelings of fullness, sink. A study in the May issue of Psychoneuroendocrinology found a significant disruption in nighttime ghrelin levels in chronic insomniacs. According to the study, this hormone imbalance leads insomniacs to experience an increase in appetite during the day, leading to weight gain over time.

In addition to creating an imbalance in ghrelin and leptin, sleep deprivation causes levels of the stress hormone cortisol to rise, which increases cravings for high-carb, high-calorie “comfort foods.” Furthermore, the brain secretes growth hormone during the deep-sleep phase, helping the body convert fat to fuel. Without enough deep sleep, fat accumulates.

Sleep expert Michael Breus, clinical director of the sleep division at Southwest Spine & Sports in Scottsdale, Ariz., says that there is no magic number of hours people should sleep but that the average adult needs about five 90-minute sleep cycles per night, so 7.5 hours seems optimal as a minimum.

But simply getting under the covers is probably not a sufficient strategy to achieve long-term weight loss, Breus says. “What these findings suggest is that there’s a new triad to achieving a healthy weight: diet, exercise and enough sleep.”

Note: This article was originally printed with the title, "You Snooze, You Lose."

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