Sleeping with TV can make you gain weight

CHICAGO (AP) – Sleeping on late-night television or sleeping with other lights can disrupt your metabolism and lead to weight gain and even obesity, a provocative yet preliminary search in the United States.

The study published Monday by the National Institutes of Health, is not a proof, but it reinforces evidence suggesting that too much exposure to light at night could pose health risks.

"We're supposed to evolve, we're supposed to sleep at night, in a dark place," said lead author Dale Sandler, a scientist at the National Institute of Environmental Health Sciences, a division of the National Institutes of health. "It's much more important than people realize for all kinds of health reasons."

Daily exposure to light and darkness helps maintain our biological clock 24 hours a day, which regulates metabolism, hormones that promote sleep, blood pressure and other bodily functions.

Growing research suggests that disrupting the typical sleep-wake cycle can contribute to poor health, increasing the risks of hypertension, diabetes, depression, and obesity.

Researchers badyzed the health and lifestyle data of nearly 44,000 US women enrolled in an ongoing study to obtain clues about the causes of bad cancer. The badysis focused on data concerning sleep, light exposure and weight gain during the study, but not on bad cancer. The results were published in JAMA Internal Medicine.

The women participating in the study underwent medical examinations and completed questionnaires about their health and lifestyle during registration and periodically thereafter. Those who reported sleeping at night in a room with a lighted television or a light were more likely to take at least 11 pounds in about five years than those who slept in the dark. They were also about 30% more likely to become obese.

Sandler said she was convinced that the extra weight did not come from things like nighttime snacks because the badysis took into account other variables that could have led to weight gain, such as diet, physical activity and sleep duration.

Sandler said that it is likely that similar results would be found in men.

Animal research and smaller studies in humans have linked prolonged exposure to light and weight gain. Scientists believe that disturbances in the release of sleep-related hormones and appetite may be involved.

Dr. Phyllis Zee, an expert in sleep disorders and circadian rhythm at Northwestern University in Chicago, said the study was important because it highlighted a behavior that can be easily modified to reduce the risk of weight gain. "A well-regulated light should be considered as part of a healthy lifestyle," she said, as well as exercise and good nutrition.

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Follow AP medical writer Lindsey Tanner on @LindseyTanner.

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