Kids who go to bed early and get up early are less likely to become obese than those who do not, according to an Australian study released Friday.

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, researchers from the University of South Australia found.

Kids who stayed up late were also almost twice as likely to be physically inactive and 2.9 times more likely to sit in front of the TV or play video games for more hours than guidelines recommend.

The study, due to be published in the journal Sleep on Saturday, studied the bedtimes and rising times of 2,200 Australian children aged nine to 16.

"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.

"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," Maher added.

Maher believes the trend may be down to early risers getting more exercise earlier in the day. She said mornings were more conducive to physical activity than nights, as kids were often distracted with prime-time TV and other sedentary activities in the evening.