It’s not news that inadequate sleep can lead to weight gain and contribute to obesity in adults. What is less studied, though, is the link between chronic sleep deprivation and weight gain, increased overall body fat (called adiposity), and obesity in kids.

In what may be the most comprehensive picture of the association between lack of sleep and childhood obesity, researchers at Harvard Medical School and Massachusetts General Hospital for Children found that children who consistently got less than the recommended amount of sleep had increased risk of obesity, as well as greater central and overall body fat.

For children six months to two years old, inadequate sleep was defined as less than 12 hours per day; it was less than 10 hours per day for ages three and four; and less than nine hours per day for children aged five to seven.

Elsie Taveras, lead author of the study, told TheDoctor, “Contrary to some published studies, we did not find a particular ‘critical period’ for the influence of sleep duration on weight gain. Instead, insufficient sleep at any time in early childhood had adverse effects.”

Several studies have suggested an association between sleep and obesity in young children, but few have looked at the effects of consistent sleep deprivation over time or used measurements other than body mass index (BMI), a measure of obesity based solely on height and weight.

Researchers analyzed data from more than a thousand children enrolled in a long-term study. They used information reported by mothers at in-person interviews when their children were about six months, three years and seven years old, and from questionnaires completed each year when the children were between the ages of one and seven years old.

At each visit mothers were asked how many hours their children usually slept each day, including naps. At the seven-year visit each child's total body fat, abdominal fat, lean body mass, and waist and hip circumference were measured.

For children six months to two years old, inadequate sleep was defined as less than 12 hours per day; it was less than 10 hours per day for ages three and four; and less than nine hours per day for children aged five to seven. Each child in the study was assigned a sleep score based on their mother's reports at each age — ranging from 0 which represented the most reports of insufficient sleep, to 13, indicating no reports of insufficient sleep.

Children with the lowest sleep scores had body measurements reflecting the highest levels of obesity and adiposity, including abdominal fat, which is thought to be particularly dangerous to health. The association was consistent for every age, suggesting that the association between sleep and weight is consistent throughout childhood, and possibly the lifespan.

Daily Routines And Sleep Hygiene
More research is needed to understand how sleep duration affects body composition, Taveras said, but the effect of sleep on hormones that control hunger and fullness and the disruption of circadian rhythms are possible mechanisms.

Household routines can also lead to both reduced sleep and increased food consumption. Insufficient sleep creates more opportunities to eat, especially if children are sedentary and watch a lot of TV, when snacking and exposure to commercials for unhealthy foods are common, said Taveras, chief of the division of academic pediatrics and director of pediatric population management at Massachusetts General Hospital for Children.

She recommends that kids and their parents learn ways to get a better night's sleep, such as setting a consistent bedtime, limiting caffeinated beverages late in the day, and forbidding high-tech distractions such as TVs, tablets, and smartphones in children's bedrooms. “Good sleep habits can boost alertness for school or work, improve mood, and enhance the overall quality of life,” she added.

The study is published in Pediatrics.