Sleep Deprivation May Cause Weight Gain
By Nanci Hellmich, USA TODAY

Scientists have known for years that not getting enough sleep makes people tired and cranky. It can raise their risk of being in a traffic accident, or making mistakes at work and home. But preliminary results of a new study also suggest that sleep deprivation may promote weight gain, at least for the short term.

Eve Van Cauter, a professor of medicine at the University of Chicago, and colleagues are studying more than 30 young men and women who are lean and fit. Some of them sleep less than 6 hours a night; they are categorized as short sleepers. The others sleep 7 to 8 hours a night and are labeled normal sleepers.

So far, results of the study indicate that the short sleepers have an impaired ability to dispose of glucose using insulin, which may put them on the pathway to obesity, says Van Cauter, who will present the study at a professional sleep meeting in June.

Researchers don't know whether people who have short-changed themselves of sleep on a regular basis can improve insulin sensitivity by sleeping more.

In a previous study, Van Cauter and colleagues followed 11 men in their 20s who were allowed to sleep only four hours a night. After a week, the men's metabolic levels and their ability to process carbohydrates had diminished. In the long term, such alterations could foster obesity, diabetes, high blood pressure and mental sluggishness, Van Cauter says.

The sleep loss affected many biological processes, including thyroid function and levels of the stress hormone cortisol, which was abnormally high in the evening in the sleep-deprived men, she says. But after the men made up for the sleep loss, they showed no signs of permanent damage, and their metabolic levels returned to normal. "The changes could be reversed in young men submitted to just one week of sleep loss, but we do not know whether the alterations can be reversed if sleep loss is more chronic," she says.

Van Cauter is not sure how lack of sleep might lead to weight gain. "We believe it's quite complex," she says. It may be a physiological response to the stress hormone cortisol, she says. It's also possible because the brain senses a lack of energy and encourages the person to eat, even if they've had enough calories for the day, she says.

James Walsh, executive director of the Sleep Medicine and Research Center at St. Luke's Hospital in St. Louis, says this work "is significant because researchers are finally assessing the impact of sleep loss on basic physiology, and I think that's a major step forward."

Obesity researcher George Blackburn, of Harvard-affiliated Beth Israel Deaconess Medical Center in Boston, says: "A good night's sleep is important to weight management, appetite and hunger control. You need to awaken refreshed so you can plan healthy eating and exercise for each day."

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