Is your child getting enough zzzs? Because children who don't are more likely to be overweight, according to a New Zealand study.

The University of Otago study of nearly 250 children has found that children aged three to five who slept less than the average of 11 hours a night were far more likely to have a higher body mass index by the age of seven.

Every additional hour of sleep per night was associated with a 61 percent decrease in risk of being overweight or obese at age seven.

This is after taking into account other lifestyle factors, such as the child's birth weight, ethnicity, the mother's education and income.

But what's behind the sleep-weight connection? The authors believe poor sleep alters hormones controlling appetite and metabolism, telling the brain to eat more. Also, less sleep means longer waking hours, which translates to more time for snacking.

The American Academy of Sleep Medicine recommends that pre-school children get between 11 and 13 hours of sleep per night, while school-age children should get 10 to 11 hours.