CHICAGO Insufficient sleep can negatively affect preteens' metabolism as well as their exercise and eating habits, causing them to get fat, researchers reported on Monday.
Children aged 9 to 12 who slept less than nine hours a night were more likely to gain weight than their more rested peers, according to researchers at the University of Michigan's Center for Human Growth and Development.
"Many children aren't getting enough sleep, and that lack of sleep may not only be making them moody or preventing them from being alert and ready to learn at school, it may also be leading to a higher risk of being overweight," said Dr. Julie Lumeng, primary author of the report.
In elementary school, children should be getting 10 to 12 hours of sleep a night, according to the National Sleep Foundation.
In a statement released by the school, Lumeng said well-rested children may be more energetic and more likely to go out and play, rather than lying around watching TV. Tired children may seek out food when they become irritable or moody, she added.
But what may be more significant is the effect sleep has on the secretion of hormones that regulate fat storage, appetite and glucose metabolism, she said. Not enough sleep can change carbohydrate metabolism and cause impaired glucose tolerance, which can affect weight, she added.
Her report was published in the November issue of "Pediatrics," the journal of the American Academy of Pediatrics.
The findings were based on an analysis of sleep patterns and other data from a government survey of 785 children aged 9 to 12. Eighteen percent were overweight by the time they reached the sixth grade.
The 12-year-olds who slept less than nine hours a night were more likely to be overweight than those who slept more, and those who got less sleep at age 9 were more likely to be overweight three years later, the study found.
The impact of sleeping less was consistent regardless of gender, race, socioeconomic status or quality of the home environment.
"Our findings also provide additional support for policies that propose later school start times," the study concluded. "The very early school start times for U.S. adolescents have raised concerns in the pediatric community because of their apparent adverse impact on sleep duration and, consequently, children's general academic and behavioral functioning."