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Sleeping longer may counter effects of "obesity genes"


(CBS News) Recent research suggests not getting a full night's sleep can raise a person's risk for obesity. A new study may have found a way to reverse the effect:

The study found people who slept more than nine hours each night may suppress genes that contribute to weight gain.

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So much for conventional wisdom that says sleeping all day will make you fat.

For the new study, published in the May 1 issue of the American Academy of Sleep Medicine's journal Sleep, researchers examined sleep habits from 1,088 pairs of twins - 604 identical, 484 non-identical - to see what effect sleep duration had on the genetic and environmental influence of weight gain, as measured by body mass index (BMI). BMI is a ratio that divides a person's weight by the square of their right, and a BMI over 25 signifies overweight and a BMI over 30 suggests obesity.

Previous studies have shown that genetics may influence obesity-contributing factors including glucose metabolism, energy use, fatty acid storage and feelings of fullness, leading some to dub them "obesity genes".

By studying the twins, who averaged age 36, the researchers determined that for those who slept less than seven hours per night, genetic influences accounted for 70 percent of BMI changes with environmental factors such as diet and exercise accounting for the rest. For twins sleeping more than nine hours, genetic factors were attributed to only 32 percent of weight changes.

"The less sleep you get, the more your genes contribute to how much you weigh," study author Nathaniel Watson, an associate professor of neurology and co-director of the University of Washington Medicine Sleep Center in Seattle, told USA Today.

Watson said the results suggest shorter sleep may allow for an environment where obesity genes flourish or that extended sleep suppresses expression of obesity genes.

"In theory, you have control over environmental factors, so the choices you make may have a bigger impact on your weight the longer you sleep," Watson told ABC News.

Earlier studies have found a link between lack of sleep and obesity risk. A study presented at an American Heart Association meeting in March found people who get about a third less than their average amount of sleep time consumed more than 500 additional calories each day, HealthPop reported. The researchers said if that rate persisted a person could gain about a pound per week.

Sleep expert Jodi Mindell, a psychology professor at Saint Joseph's University in Philadelphia, told USA Today of the new study, "If you're trying to lose weight, getting enough sleep gives you a fighting chance."

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