Young children who do not get enough sleep are more likely to be overweight at the age of seven, researchers say.
A lack of sleep increases the risk a child will become overweight even after accounting for lifestyle factors, such as whether they exercise or have a healthy diet, research has found.
Experts in New Zealand studied 244 children for the research, published in the British Medical Journal.
Their weight, height, body mass index (BMI), and body composition, including body fat, were measured every six months from age three to seven. How much they slept and their physical activity was also assessed via a device worn on a belt that measures body movement.
When the children were aged three, four and five, questionnaires determined their dietary intake.
Other factors, such as birth weight, mothers' education, income, maternal BMI, smoking during pregnancy and ethnicity were also recorded because they have been shown to influence a child's weight.
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 body weight, they said.
Researchers noted 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.
The experts concluded: "Young children who sleep less have a significantly increased risk of having a higher BMI in middle childhood, even after adjustment for multiple risk factors that have been implicated in regulation of body weight.
"While the differences "may seem minor at an individual level, the benefits for public health, if applied at the population level are considerable," they added.
PA