Early bedtime ‘helps a child to stay slim’

A lack of sleep increases the risk a child will become overweight even after accounting for lifestyle factors, such as exercise or have a healthy diet.

Experts in New Zealand studied 244 children for the research, published in the British Medical Journal (BMJ).

Their weight, height, body mass index (BMI), and body composition, including body fat, were measured every six months from age three to seven and how much they slept and their physical activity was assessed via a device worn on a belt.

When the children were aged three, four and five, questionnaires determined their dietary intake while other factors, such as birth weight, mothers’ education, income, maternal BMI, smoking during pregnancy and ethnicity were also recorded.

The researchers found that, on average, children slept 11 hours per day at all three ages but those children who slept an extra hour per night at ages three to seven had a reduction in BMI of 0.48 and a 61 per cent reduced risk of being overweight when they were seven.

In a child of average height, this corresponds to a difference of 0.7kg. And they noted that the lower BMI was due to less body fat, suggesting poor sleep has negative effects on body composition.

One theory is that a lack of sleep may lead to children eating more and could influence how much energy they use.