Sleep less and weigh more?

Elementary school children who don’t get enough sleep in third grade are more likely than their peers to be overweight in sixth grade, according to a large study believed to be the first to examine the relationship between excess fat and sleep in children. Studies of adults have found a similar association between sleep duration and excess weight.

Researchers led by pediatrician Julie C. Lumeng at the University of Michigan reported earlier this month in the journal Pediatrics that children between ages 9 and 12 who routinely got less than nine hours of sleep per night were at increased risk of being overweight, regardless of their sex, race, socioeconomic status or the level of chaos in the home.

Lumeng and her colleagues also found no association between sleep problems, such as trouble falling asleep or staying in bed, and excess weight.

Using data from a large federally funded study of youth development, researchers found that among sixth-graders, for every additional hour of sleep beyond nine hours, a child was 20% less likely to be overweight.

Half of the nearly 800 children in the study were boys, and 81% were white.

Overall, 18% were overweight; boys were more likely to be overweight than girls.

The authors write that the findings suggest “a biological link between sleep duration and obesity” possibly caused by alterations in metabolism and the secretion of hormones that help control weight. Regardless of the mechanism, they conclude that their findings provide “an additional reason to ensure that children are receiving adequate sleep, primarily through enforcing an age-appropriate bedtime.”

The National Sleep Foundation recommends that elementary school students sleep between 10 and 12 hours per night.