Twins Study Finds Getting Less Than 7 Hours of Sleep a Night Can Make You Gain Weight

Posted on May 3, 2012

A new study on twins - described as a genotype-environment interaction twin study - has found that a shorter sleep duration is associated with increased Body Mass Index (BMI) and increased genetic influences on BMI. The study suggests that shorter sleep duration increases expression of genetic risks for high body weight. At the same time, the researchers say longer sleep duration may suppress genetic influences on body weight.

The study, published in the journal, SLEEP, 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. In this study, the researchers say they found the heritability of BMI was twice as high for the short sleepers than for twins who slept longer than nine hours a night. Nine hours of sleep a night is a lot of sleep and more than most people get. Apparently, most teenagers need 8.5 to 9 hours of sleep a night, so get to bed teens.

Nathaniel Watson, MD, MSc, of the University of Washington, the principal investigator in the study, says, "The results suggest that shorter sleep provides a more permissive environment for the expression of obesity related genes. 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% of the differences in BMI, with common environment accounting for just 4% and unique environment 26%. For twins averaging more than nine hours of sleep, genetic factors were attributed to 32% of weight variations, with common environment accounting for 51% and unique environment 17%.

Watson acknowledges that more research is needed, but he says 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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