"An Early Bedtime Might Keep Teens Fit" by Meredith Melnick points out how teens with an earlier bedtime and who awoke earlier spent more time in their day staying active and performing non-sedentary acts. The study in Australia involved 2,200 teens. It measured their sleeping habits, weight, and use of free time.
One factor brought up within the article is the amount of time overweight teens spend in front of the television and at what times. The overweight children were watching television late at night before attempting to go to bed. In our textbook, it is recommended for those who suffer from insomnia, or any sleep condition, to not watch television or surf the Internet before bed.
Using the critical thinking step of ruling out rival hypothesis, I think that the lurking variable (that was addresses within the article) of how they are spending the time before they are going to bed is effecting the amount of good, uninterrupted sleep they are getting throughout the night.
While a solution to the problem of daily habits may be going to bed at an earlier time, I also feel that the time is less important then what the teenager has done in those minutes before bed. Overweight and obese teens are more likely to plop in front of the couch before bed and watch for a few hours. Encourage teens to go on a walk instead, let them calm their minds and then go to bed, hopefully waking up rested, no matter what time it is at.