When children are given the opportunity to sleep more, like on weekends and holidays, the extra sleep tends to counter the negative effects -- including extra body weight -- of irregular sleep on weekdays.
A study that looked at sleep duration and its effect on body weight was published in the February edition of Pediatrics, the scientific journal of the American Academy of Pediatrics.
Children ages 4 to 10 participated in the study, all of whom got about eight hours of sleep during the week, much less than is recommended.
On the weekends, though, obese children had shorter and more irregular sleep than normal weight children. Also, they were less likely to catch up on the sleep lost during the week. The combination of less sleep and more variable sleep was associated with "adverse metabolic outcomes," according to the study.
So don't be surprised if you start seeing public service announcements aimed at parents, asking if their children are getting as much sleep as they need. The study's authors say such campaigns may help children maintain a health body weight.