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. Researchers 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 in the Washington state area. Twins sleeping less than seven hours a night were associated with increased BMI and greater genetic influences on BMI. Other studies have shown that genetic influences on weight include things like glucose metabolism, energy use, fatty acid storage, and satiety. This study determined that the heritability of BMI was twice as high for short sleepers than for twins sleeping longer than nine hours a night.
The results demonstrate a gene-environment interaction between sleep habits and BMI, researchers said. This suggests that shorter sleep provides a more permissive environment for the expression of obesity-related genes. Or that extended sleep protects by suppressing the expression of obesity genes.
More research is needed, the study concluded, but these preliminary results suggest that behavioral weight loss measures would be most effective when genetic influences are weakened through sleep extension. The study appeared in the May issue of SLEEP.
