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Sleep timing, not quantity keeps kids lean

Kathleen Blanchard's picture

Children who get to bed early and rise early are slimmer than their counterparts who stay up late and sleep in. In a study, investigators found timing of sleep plays an important role in keeping kids lean and active.

For this study, scientists recorded the time 2,200 Australian participants, ages 9 to 16, went to bed and when they awakened.

Timing of sleep important for child health

"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 co-author Carol Maher, PhD, a postdoctoral fellow with the University of South Australia.

Scientists have realized 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."

Staying up late and sleeping in could lead to childhood obesity

The researchers looked at the children’s activity during the day and sleep times over a period of four days.

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They found that adolescents who stay up late and got up late were 1.5 times more likely to become obese, compared to kids who went to bed early and got up early.

Late to bed adolescents spent an average of 48 more minutes watching TV, playing video games or online, mostly between 7pm and midnight, compared to kids who went to bed and awakened earlier.

The study, published in the journal SLEEP, also found children who get up early engage in 30 more minutes of physical activity than their ‘late night’ counterparts – perhaps from fewer prime-time TV programs and social networking opportunities in the morning hours.

"It is widely accepted that the sleep patterns of adolescents are fundamentally different from children and adults, and that it is normal for adolescents to stay up very late and sleep in late in the morning," Maher said." Going to bed late and getting up late seems to promote “unfavorable activities and health outcomes", Maher adds.

Kids who go to bed late and sleep in were more obese, found by the researchers. They also tended to come from lower income households, have part time jobs and few siblings.

Preventing childhood obesity has become a recent focus of public health efforts. The study shows pre-teens who get to bed early and get up early are less likely to become overweight or obese, with a tendency to be more physically active.

The research finding suggests timing of sleep is important for preventing childhood obesity. In the study, kids who stayed up late and slept in got the same amount of sleep hours as those who were ‘early to bed, early to rise’, but tended to be more obese and less physically active.

Image credit: Moreguefile