Toss out another old wives’ tale: Sleeping too much does not make you fat. Quite the opposite, according to a new study examining sleep and body mass index (BMI) in twins, which found that sleeping more than nine hours a night may actually suppress genetic influences on body weight.

The study looked at 1,088 pairs of twins and found that sleeping less than seven hours a night was associated with both increased BMI and greater genetic influences on BMI. Previous research has shown that genetic influences include things like glucose metabolism, energy use, fatty acid storage and satiety. In this study, the heritability of BMI was twice as high for the short sleepers than for twins who slept longer than nine hours a night.

“The results suggest that shorter sleep provides a more permissive environment for the expression of obesity related genes,” said principal investigator Nathaniel Watson, MD, MSc, of the University of Washington. “Or it may be that extended sleep is protective by suppressing expression of obesity genes.”

Watson and colleagues determined that for twins sleeping less than seven hours, genetic influences accounted for 70 percent of the differences in BMI, with common environment accounting for just 4 percent and unique environment 26 percent. For twins averaging more than nine hours of sleep, genetic factors were attributed to 32 percent of weight variations, with common environment accounting for 51 percent and unique environment 17 percent.

More research is needed, Watson said, but these preliminary results may suggest that behavioral weight loss measures would be most effective when genetic drivers of body weight are mitigated through sleep extension.
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For a copy of the study, “Sleep Duration and Body Mass Index in Twins: A Gene-Environment Interaction,” or to arrange an interview with an AASM spokesperson, please contact PR Coordinator Doug Dusik at 630-737-9700, ext. 9364, or .(JavaScript must be enabled to view this email address).

The monthly, peer-reviewed, scientific journal SLEEP is published online by the Associated Professional Sleep Societies LLC, a joint venture of the American Academy of Sleep Medicine and the Sleep Research Society. The AASM is a professional membership society that is the leader in setting standards and promoting excellence in sleep medicine health care, education and research.

Help for people who have a sleep problem is available at more than 2,400 AASM-accredited sleep disorders centers around the United States.

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Doug Dusik
.(JavaScript must be enabled to view this email address)
630-737-9700
American Academy of Sleep Medicine