A new study has found that children who don't get enough sleep are at risk of putting on more weight than those who get a good night's kip.
Leslie Lytle and a team from the Centre for Child Health, Behaviour and Development at Seattle Children's Research Institute, looked at the sleep habits of 723 teenagers.
They found that the less sleep children got, the more they weighed.
Apparently you burn more fat while you're asleep than you do by playing video games or sending text messages.
Lytle says in a press release from the Pediatric Academic Societies: "Sleep has long been recognized as an important health behaviour.
"We are just beginning to recognise its relationship to overweight and obesity in children and adults alike."
There have been previous studies showing a link between sleep and weight, particularly in young children.
However this is one of the first studies to connect sleep and weight in teenagers after adjusting the results to take into account calorie intake, activity level and depressive symptoms.
Researchers looked at how long the teenagers slept on week nights and weekends, and how often they had problems sleeping.
They were also asked about the food they had eaten the previous day, and their movements were measured with an accelerometer.
Researchers measured kids' weight, body mass Index and percentage of body fat, and found that those children who slept less had a higher BMI.
There was a particularly strong relationship between lack of sleep and high BMI among boys. It also seemed to have a bigger effect on middle school students than on high school students.
Sounds like we should be letting teenagers sleep more, instead of nagging them to get out of bed...