Obese teenagers are more likely to develop Type 2 diabetes if they do not get enough sleep, a new U.S. study suggests.

"Our study found to keep glucose levels stable, the optimal amount of sleep for teenagers is 7.5 to 8.5 hours per night," said Dr. Dorit Koren, the chief investigator.

The study, published in the journal Diabetes Care, was conducted at the Children's Hospital of Philadelphia and involved 62 obese teenagers as subjects. The teens were subjected to a series of glucose tests and an overnight sleep study. The researchers also tried to observe stages of sleep like rapid eye movement and slow-wave deep sleep.

Inadequate sleep and excessive sleep can both be associated with high glucose production, according to Koran. There were no signs that different stages of sleep trigger more production of glucose, but there was an association of deep sleep with decreased secretion of insulin.

"Reduced insulin secretion may lead to higher glucose levels than we found in subjects who had in sufficient sleep," Koren said. Further investigation will be done of the sleep patterns of obese adolescents.

Diet and exercise remain vital to controlling weight and preventing diabetes, but now sleep can be added to the prescription.