A recent study, published online by the International Journal of Obesity, reveals that the amount of sleep a child gets can have a significant impact on his weight.
The study looked at 422 children -- half boys, half girls -- between the ages of 5 and 10. The investigators measured each child's waist size, height, and weight, and asked each child's parent, via telephone, how much sleep his or her child got on an average night.
Twenty percent of the boys and 24 percent of the girls studied were overweight or obese, the investigators found. But children who slept less than 10 hours a night were 3 1/2 times more likely to be overweight than those who slept 12 hours or more. No other factor analyzed in the study -- parental obesity, parents' level of education, family income, time spent in front of the TV or computer, or regular physical activity -- had quite as big an impact on the likelihood of obesity.
Previous research has linked lack of sleep with an increase in the hormone ghrelin, which causes hunger, and a decrease in the hormone leptin, which reduces hunger. But this was one of the first studies to show a direct link between sleep and weight. This direct correlation will allow scientists to "add sleep duration to the environmental factors that are prevalent in our society and that contribute to weight gain and obesity," according to Professor Angelo Tremblay and other authors of the study.
So how much sleep should your child be getting? That varies by age and activity level, according to the Guide to Your Child's Sleep, published by the American Academy of Pediatrics. In general, kindergartners should get 10 to 12 hours per night. This amount can decrease slightly each year, depending on a child's activity level. By the teenage years, about nine hours is enough.
"It's ironic that part of the solution to obesity might lie in sleep, the most sedentary of all human activities. In light of this study's results, my best prescription against obesity in children would be to encourage them to move more and to make sure they get enough sleep," concludes Tremblay.