Kids Who Skimp on Sleep Tend to Be Fatter

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The researchers also took into account maternal education, race, the quality of the home environment and parenting skills to see if those factors affected a child's weight.

No matter what a child weighed in third grade, too little sleep correlated with being obese in sixth grade. And, short sleep duration in sixth grade also correlated with excess weight in sixth grade, according to the study.

Third-graders who got less than nine hours and 45 minutes of sleep a night had an obesity prevalence of about 20 percent, while those who got more than nine hours and 45 minutes of sleep had obesity rates of about 12 percent, Lumeng said.

Those who were short-changing sleep in third grade had 40 percent higher odds of being obese in sixth grade, and sixth-graders who weren't getting enough sleep were 20 percent more likely to be obese, compared to their well-rested counterparts.

Lumeng said the researchers weren't able to find a statistical association between quality of sleep and obesity. But, she said that without a lab-based sleep study, it's difficult to objectively assess the quality of sleep, so there may be an association that this study wasn't able to uncover.

Dr. Stephen Sheldon, director of the Sleep Medicine Center at Children's Memorial Hospital in Chicago, said he would've liked to see sleep studies so the researchers could have known more about the quality of sleep these children were getting, such as how much REM sleep did they get and how fragmented was the sleep?

But, he said, the bottom line is that "pediatricians and parents really need to start paying closer attention to sleep-wake habits. In this society, we put a premium on being awake, and that premium may hurt us in the long run. Sleep may be as important as food to our health and well-being," said Sheldon, who's also a professor of pediatrics at the Northwestern University Feinberg School of Medicine.

Both Lumeng and Sheldon recommended trying to keep a consistent sleep schedule. Bedtimes and wake times are both important -- for children and adults. Sheldon said it's usually OK to vary your sleep times a little bit on the weekend, about an hour or so, but, he cautioned, "Letting you child sleep till noon or mid-afternoon is inviting trouble."

Lumeng also recommended that children not have a TV in their bedroom, because it can make it more difficult to fall asleep.

More information

To read more about the connection between overweight and sleep, visit the National Sleep Foundation.