THURSDAY, May 25, 2006 (HealthDay News) -- Getting a decent night's sleep apparently does more than provide good rest -- it seems to curb the number of pounds women put on as they age, according to a new study.
Although the study didn't show a definite cause-and-effect relationship, there was a significant link between inadequate sleep and weight gain, said lead investigator Dr. Sanjay Patel. Women who got only five hours of sleep a night, on average, gained substantially more weight than those who routinely had seven hours' worth of shuteye.
"We do know that sleep-deprived people generally pay less attention to their health," said Patel, an assistant professor of medicine at Case Western Reserve University, in Cleveland. However, there's no proof that any one factor, from a poor diet to lack of exercise, accounted for the weight difference, he said.
In fact, women who got seven hours or more of sleep actually ate more than those who got five hours' sleep. And the exercise habits were about the same, too -- although the group that slept a healthier seven hours tended to exercise a little more, Patel said.
The women were part of the Nurses Health Study, which followed more than 68,000 women for 16 years. They were asked to report their weight and lifestyle regimen every two years. By the end of the study, women who slept five hours a night were 32 percent more likely to experience major weight gain -- defined as an increase of 33 pounds or more -- and 15 percent more likely to become obese, compared with women who slept seven hours. And women who slept for six hours were 12 percent more likely to experience major weight gain and 6 percent more likely to become obese over the study period, compared with women who slept seven hours a night.
There are several possible explanations for the findings, Patel said. It could be that sleep deprivation causes the body to metabolize calories less efficiently. Or it may be that the actual forms of exercise or the exact patterns of eating differed between the two groups of women in the study. It may also be that a lower number of hours spent sleeping reflects a basic life change that can have a fairly dramatic impact -- like becoming a parent, he said.
"The more kids you have, the less sleep you get," Patel said. That might lead to the kind of multi-tasking demands in which convenience, such as fast food, trumps nutritional vigilance, he said.
"There are many possible explanations," agreed Dr. John Kimoff, director of the Sleep Disorders Centre at McGill University in Montreal. "But you have to be very careful about speculating on the mechanisms."
One intriguing area of research has suggested that sleep disturbances, such as deep snoring and night-time awakenings, may affect weight, perhaps due to a subtle inherited trait that shows increasing impact with age.
The study findings were presented Tuesday at the American Thoracic Society International Conference, in San Diego.
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