Sleep adequately to maintain healthy weight

By Dr. Ananya Mandal, MDMay 3 2012

A study on twins has shown that getting adequate sleep may help with maintaining a healthy body weight.

The genes behind weight gain may work overtime with lack of sleep says the study in this week's issue of the journal Sleep. In the study, neurologist Dr. Nathaniel Watson of the University of Washington Medicine Sleep Center in Seattle looked at the height, weight and sleep habits of 604 pairs of identical twins and 484 fraternal twins with an average age of 37.

The team found that sleeping less than seven hours a night was associated with increased body mass index (BMI). On average, the people in the study slept 7.2 hours a night, which falls within the National Sleep Foundation’s recommended seven to nine hours. People who slept less than seven hours a night, however, had a higher BMI than those who slept more than nine hours.

“What we see is that as sleep durations were reduced, the genetic risks of having a high body weight went up,” Watson. “So it's suggesting that when you're sleeping less, you're turning on these genetic drivers to how much you weigh.”

The heritability of BMI was twice as high among short sleepers than twins who slept longer than nine hours a night, the researchers estimated. Three factors drive BMI among twins, Watson said, genetics, shared environment such as diet and parenting and non-shared environment that makes twins different from each other. The study's authors said genetic factors determined 33 per cent of how long twins slept.

Previous research showed genetic influences such as glucose metabolism, energy use and satiety influence BMI. The genetic pathways involved aren't known. Authors caution that this study does not mean sleeping well means healthy body weight. Sleep needs to be in conjunction with diet and physical exercise.

“The paper is supporting the long-time belief that there is an association between body mass index and duration of sleep, but the effect of more sleep may not be as powerful as we believed,” said Dr. David Schulman, medical director of the Emory Sleep Disorders Laboratory. Schulman was not involved in the study.

“There is too much sleep and there is little sleep. There is an amount of sleep where people become less healthy,” said Watson. “Most people need between 7 and 9 hours a night.” “We've been telling people about the negative effects of too little sleep, so this paper supports that as well,” Schulman said.

Watson said he hopes that research will next focus on determining precisely how genes are involved, which could eventually lead to a drug that targets obesity, something that other sleep specialists find exciting.

“This study shows that a particular population is affected by sleep deprivation and excess sleep and sheds light on that fact that we should investigate whether other populations are also affected in this way,” said Dr. Alexandre Abreu, director of the University of Miami Sleep Center. “The fact that having sleep deprivation may trigger a genetic component that can increase body mass index and weight can be a great focus for targeting obesity in our population.”