Early bedtime children 'slimmer'
Sending children to bed early may help to keep them slim, research suggests.
Scientists recorded the bed times and waking times of 2,200 Australian youngsters aged nine to 16.
They found that children who went to bed late and got up late were 1.5 times more likely to become obese than those who went to bed early and got up early.
Late-nighters were also almost twice as likely to be physically inactive and 2.9 times more inclined to spend hours in front of a TV or computer.
"The children who went to bed late and woke up late, and the children who went to bed early and woke up early got virtually the same amount of sleep in total," said study author Dr Carol Maher, from the University of South Australia.
"Scientists have realised in recent years that children who get less sleep tend to do worse on a variety of health outcomes, including the risk of being overweight and obese. Our study suggests that the timing of sleep is even more important."
For young people, mornings are more conducive to physical activity than nights, when the temptations of prime-time TV and social networking are greater, Dr Maher pointed out.
The findings are published in the October 1 issue of the journal Sleep.
Children who were early-to-bed and early-to-rise went to bed 70 to 90 minutes earlier on average than those who stayed up later, the study found. They also accumulated 27 minutes more moderate to vigorous activity each day.
Body Mass Index (BMI) scores, which relate weight and height, were higher for late-risers than early-risers. Late-risers were more likely to be overweight or obese.