Teenage boys who don't get enough sleep are at higher risk of having excess body fat, according to new research from the University of Otago.
In contrast, the amount of sleep teenage girls fit in each night has no discernable effect on their level of body fat or waist circumference.
In the study, researchers from the university's Department of Human Nutrition looked at 386 boys and 299 girls aged between 15 and 18, from 11 different secondary schools in the Otago region. They found teenage boys who sleep up to eight hours a day have 9 percent more body fat and waists 1.8cm wider than those who slept 10 hours, on average.
The group who slept less also have more bone and muscle mass, but at an increase of only 1.4 percent, this is dwarfed by the increase in fat.
"Our results suggest that for older teenage boys, making sure that they get adequate sleep may help to maintain a healthier a body," says lead researcher Dr Paula Skidmore.
"It seems to be that, within reason, the more sleep the better, for boys."
A number of studies in the past have shown teenagers generally require more sleep than children and adults, and their body clocks are more suited to staying up late and sleeping in. One study reported in New Scientist earlier this year suggested getting up at 7am was as difficult for a teenager as getting up at 5am is for someone in their 50s.
The Otago study ruled out the effects of diet and electronic devices – such as game consoles and TVs – the teenagers had in their bedrooms.
Because diet was ruled out as a cause of the increase in body fat, Dr Skidmore says she didn't expect to see any differences between the sexes.
"It was unexpected that we did not find the same result in girls, who may actually be more aware of their diet and more in tune with a healthier lifestyle," says Dr Skidmore.
Though sleep appears to be more important for boys than girls – at least when it comes to body fat and shape – the study found no difference between the sexes when it came to the amount they needed.
Both sexes slept on average about nine hours and 15 minutes a night. Around a quarter needed more than half an hour longer than this, and only a quarter slept for less than eight-and-a-half hours each night.
On weekends, both sexes slept an hour more than they did during the week – though you don't need to be a teenager to understand why this might be the case.
3 News
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