You've probably heard that increased TV watching, high-calorie snacking, and decreased physical activity are linked to skyrocketing rates of child obesity. But recent research points to a new culprit: lack of sleep.
"Children who don't sleep enough are at much greater risk for obesity than children who do sleep enough," says Frederick J. Zimmerman, PhD, chair and professor in the Department of Health Services at UCLA School of Public Health, and one of the lead researchers in a recent study.
Waking in the middle of the night to change your child's sheets after a bedwetting episode is practically a rite of passage for parents. And it's more common than you think.
"I call it the hidden problem of childhood," says Howard Bennett, MD, a pediatrician and author of Waking Up Dry: A Guide to Help Children Overcome Bedwetting. "Unlike asthma or allergies, it's just not talked about outside the house."
The study followed 1,930 children, ages 0 months to 13 years, tracking their sleep and weight patterns for five years. What they found: Children 0 to 4 years at the start of the study "who had inadequate nighttime sleep had about an 80% higher risk of obesity five years later. This is a big, meaningful difference," Zimmerman says. "If you took a group of 100 kids who were not sleeping well, about 25 or so would wind up obese who otherwise wouldn't be," Zimmerman says.
The Link Between Sleep and Obesity
That's why researchers say "there is a critical window prior to age 5," when inadequate nighttime sleep can set the stage for childhood obesity for years to come. The difference between those who got enough sleep and those who didn't? About 45 minutes, Zimmerman estimates.
The study didn't explore causal mechanisms behind inadequate sleep and weight gain, though Zimmerman suspects several factors. "Younger kids, even kids who are 6 and 8 years old, who are under-slept are uncomfortable," says Zimmerman. And they might try to feel better by eating.
Also, hormones involved in regulating appetite, leptin and gherlin, are thrown off-kilter by inadequate sleep in adults, and the same might happen in children.
Finally, there's the possibility that kids who are really tired just aren't able or don't want to do a lot of physical activity. Clearly, more research is needed in all these areas.
One surprising result of the study: Napping did not reduce the risk of obesity.
The bottom line? "Getting adequate [nighttime] sleep is one of the easiest ways to reduce the risk of obesity," Zimmerman says.