Sleep More, Weigh Less

By the All Psychology Schools career research team—Your source for Psychology Career news, trends and programs.

Researchers have amassed substantial medical evidence demonstrating a relationship between sleep and weight loss. The American Journal of Epidemiology recently published a study that showed recent mothers who get less than five hours of sleep per night are three times more likely to retain weight gained during pregnancy. The December issue of the same journal includes a study showing that sleeping problems in children between the ages of two and four increase their odds of being obese in young adulthood by 90 percent.

But sleeping too little doesn't just affect weight in kids and new moms. Not only how much you sleep but the quality of your sleep affects hormonal activity tied to appetite. The hormones leptin and ghrelin (the latter was discovered in just the last 10 years) play a role in regulating hunger. Specifically, ghrelin stimulates the appetite, while leptin sends a signal to the brain telling you when you're full.

So where does sleep enter in? A study conducted at the University of Chicago charted the levels of leptin and ghrelin in 12 healthy men as well as their hunger levels. After the men were subjected to two days of sleep deprivation, leptin levels went down and ghrelin levels rose. Their appetites increased proportionally, particularly for high carb, high calorie foods.

In another study conducted by Stanford University, more than 1,000 volunteers reported the number of hours they slept each night while doctors measured their levels of leptin and ghrelin and tracked their weight. Those who slept less than eight hours had lower levels of leptin, higher levels of ghrelin, and more body fat. What's more, those who slept the fewest hours weighed the most.

But before you cancel your gym membership or gorge on fast food, experts say that sleep is only one of many factors affecting weight and that its exact role isn't yet fully known. Most agree, however, that getting a few hours extra sleep a week isn't a bad idea if you want to lose a few pounds, especially if you typically sleep less than six hours a night. You might not only feel less tired the next day, but also less hungry.

_{Sources: The New York Times Magazine, 11/18/2007; Scientificblogging.com, 11/18/2007; Medscape Today}

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