Lack of sleep linked to obesity risk

NEW YORK (Reuters Health) - Among adults with chronic health conditions, such as heart disease and diabetes, those who are relatively sleep-deprived are more likely to be obese, a new study suggests.

It's not clear if the sleep loss was actually a cause of the weight problems in these study patients. However, past studies have suggested that chronic sleep deprivation -- through effects on the body's physiology or on people's behavior -- may encourage weight gain.

This latest study "suggests that adults should sleep 8 to 9 hours per night to maintain optimal weight," senior researchers Dr. Kenneth Nugent, of Texas Tech University in Lubbock, commented in a statement.

The findings, published in the Journal of Clinical Sleep Medicine, are based on 200 patients at the university's internal medicine clinics. All had some type of chronic health condition, such as heart disease, high blood pressure, diabetes or arthritis.

The researchers found that patients who said they typically slept for less than 7 hours each night were nearly three times more likely to be obese than patients who got 8 or 9 hours of sleep.

Among women, both short sleepers and long sleepers (more than 9 hours per night) were at greater risk of obesity. This pattern was not seen in men.

Neither the patients' medical conditions nor the treatments they received explained the link between sleep and obesity, according to Nugent's team. The same was true when the researchers looked at patients' amount of physical activity.

Other factors associated with obesity were drinking alcohol, not smoking, young age (between 18 and 49), diabetes, hypertension, and sleep apnea.

Short sleep times may be related to body weight for a number of reasons, the researchers note. One has to do with behavior -- the more time a person spends awake, the more opportunity for eating.

There is also evidence that sleep deprivation raises the body's levels of the appetite-stimulating hormone ghrelin, while lowering levels of its hunger-suppressing counterpart leptin.

All of this, according to Nugent's team, raises the possibility that a good 8 hours of sleep each night can help people control their weight -- including those with chronic health problems. More research is needed to prove this, however.

"Whether or not manipulating sleep time in adults will prevent additional weight gain or facilitate weight loss is unclear," Nugent said. "This question will require therapeutic trials in which sleep hygiene is addressed during weight loss studies."

SOURCE: Journal of Clinical Sleep Medicine, December 15, 2007.