Lack of Sleep in Babies a Cause of Childhood Obesity, Study Finds

As if parents weren't stressed enough about their kids not getting enough sleep at night, now there's a whole new reason to worry.

Babies and preschoolers who don't get at least 10 hours of sleep at night may be significantly more at risk for developing childhood obesity, according to a new study. Think your kid makes up for it with an afternoon snooze? The researchers found daytime napping doesn't seem to be an adequate substitute for nighttime sleep when it comes to preventing obesity.

These findings are significant in light of alarming childhood obesity statistics: During the last three decades, obesity has doubled among children ages 2 to 5 and among adolescents ages 12 to 19, and has tripled among 6- to 11-year-olds, the researchers report.

"This study is important because we have an obesity epidemic at the moment, with rates of obesity in children increasing steadily at least since the 1970s," lead researcher Janice Bell of the University of Washington, Seattle tells ParentDish. "There have been a lot of efforts to mitigate this trend, but they haven't been that successful."

The authors report that 17 percent of children and adolescents were reported to be obese in 2003-2004 and 34 percent were overweight. Kids and teens are considered obese if their Body Mass Index (BMI) falls into the 95th percentile or above, and overweight if their BMI is in the 85th to 95th percentile, according to the Centers for Disease Control and Prevention (CDC).

The study, which appears in the Archives of Pediatrics & Adolescent Medicine, used data from an existing survey of 1,930 children ages 0 to 13 years, separated into two age groups -- younger children (0 to 5 years) and older children (5 to 13 years). Measurements were taken at two points in time -- a 1997 baseline and a 2002 follow-up.

"It was in the very youngest children -- birth to 5 -- where we saw the effect of shortened nighttime sleep on their subsequent weight status five years later," Bell tells ParentDish. "In the older kids, we were seeing that weight and sleep were associated at that time point -- kids who were obese slept less, but the causal relationship wasn't clear -- it doesn't mean that it was the earliest sleep that mattered."

These findings suggest there is a critical window prior to age 5 when nighttime sleep may be important for subsequent obesity status, the authors report.

It is not yet known precisely how sleep works to influence weight, but one theory cited by the researchers is that the lack of sleep leads to decreased physical activity -- since the children are tired -- and causes increased food intake, given a greater opportunity to eat.

A second theory focuses on the hormones that regulate body weight, such as leptin and ghrelin, and metabolism. Hunger and appetite increase with lower leptin and higher ghrelin levels, and both low leptin and high ghrelin levels have been linked to short sleep duration in adults, Bells says, though less is known about these relationships in children.

Bell tells ParentDish there may be another explanation, which was not mentioned in the research report.

"There could also be a third factor involved that we didn't measure," she says. "For example, children with less sleep may be taking in caffeinated beverages that cause them not to sleep and also contribute additional calories, and therefore contribute to obesity."

There is a growing body of research studying the obesity-sleep connection in adults and kids, so this isn't new information, Bell says, but she says the current study was unique in that it looked at kids in the United States, over a broader age range and at two different points in time.

"This study underscores the critical importance of adequate sleep in early childhood," Bell says. "We've been focusing a lot on diet and exercise in obesity prevention, but it may be time to add sleep to the mix, as well."

Related: Michelle Obama Releases Childhood Obesity Recommendations