Losing sleep makes children fatter

The less children sleep the fatter they become, researchers report.

Hectic parental lifestyles and lax bedtimes for their offspring could be driving the explosion in child obesity, they said yesterday.

A study of 422 children aged between 5 and 10 found one in five of the boys and one in four of the girls was overweight or obese.

On average the children slept for 12 to 13 hours a night. But those who slept for 10.5 to 11.5 hours a night had a 40 per cent more risk of becoming overweight or obese.

In those who slept for eight to 10 hours a night the risk was increased more than three-fold.

The findings are published in the International Journal of Obesity. The researchers from Laval University, Quebec, Canada, say the recognised risk factors of long TV watching, physical inactivity and parental obesity applied to the children. But the effect of lack of sleep was independent of these.

"These findings are important because sleep duration is a potentially modifiable risk factor that could be important to consider in the prevention and treatment of obesity," they say.

The researchers describe their findings as "provocative" given that the best way of curbing weight is to increase activity and having extra sleep means less activity.

"It is somewhat paradoxical that sleeping, the most sedentary of all activities, may be associated with leanness.

"Although recommendations to get both a better night's sleep and more exercise might superficially seem to be at odds with each other ... these simple goals may well become part of our future approach to combating obesity."

Separate laboratory studies have shown that short sleep duration is associated with decreased levels of leptin and increased levels of ghrelin - hormones which play a key role in hunger and appetite.

Changes in the two hormones caused by lack of sleep could alter food intake over time and explain why individuals affected put on weight, the researchers say.

The results suggest a "dose-response" relationship between lack of sleep and overweight, with those children sleeping the least being at greatest risk of obesity.

The researchers conclude: "Reduction in sleeping hours has become a hallmark of our society. If the findings prove to be reproducible and generalisable ... we could add sleep duration to the environmental factors that are prevalent in our society and that contribute to weight gain and obesity."

- INDEPENDENT