The less a child sleeps, the more likely he or she is to become obese. Researchers at the Johns Hopkins Bloomberg School of Public Health in the United States have carried out a study and found that with each additional hour of sleep, the risk of a child being overweight or obese drops by nine per cent.

According to lead researcher Youfa Wang, "Our analysis of the data shows a clear association between sleep duration and the risk for overweight or obesity in children. The risk declined with more sleep.

"Desirable sleep behaviour may be an important low cost means for preventing childhood obesity and should be considered in future intervention studies. "Our findings may also have important implications in societies where children do not have adequate sleep due to the pressure for academic excellence and where the prevalence of obesity is rising."

The researchers came to the conclusion after reviewing 17 published studies on sleep duration and childhood obesity and they analysed 11 of them in their meta-analysis. The recommended amount of daily sleep varied between studies analysed and with children's age.