August 4 (HealthDay News) -- Getting too little sleep or not spending enough time in rapid eye movement (REM) sleep is associated with being overweight among children and teens, a new U.S. study.

For three consecutive nights, researchers assessed the sleep patterns of 335 youngsters, aged 7 to 17. They looked at total sleep time, time spent in REM, and time it took to fall asleep. Body-mass index was checked at the start of the study, and 45 participants (13.4 percent) were overweight, while 49 (14.6 percent) were at risk for becoming overweight.

Compared to normal-weight children, those who were overweight slept about 22 minutes less per night and had lower sleep efficiency (percentage of time in bed that a person is asleep), shorter REM sleep, less eye activity during REM sleep, and a longer wait before the first REM period.

After they adjusted for other factors, the researchers concluded that one hour less of total sleep was associated with a twofold increased risk of being overweight. One hour less of REM sleep was associated with a threefold increased risk.

Although the precise mechanisms are currently under investigation, the association between short sleep duration and overweight may be attributed to the interaction of behavioral and biological changes as a result of sleep deprivation, wrote Dr. Xianchen Liu, of the Western Psychiatric Institute and Clinic in Pittsburgh, and colleagues.

They explained that sleep loss causes changes in hormone levels that may affect hunger, and less sleep also means a person has more waking hours in which to eat. Sleep loss also contributes to fatigue the following day, which may lead to less physical activity and fewer calories burned.

Given the fact that the prevalence of overweight among children and adolescents continues to increase and chronic sleep insufficiency becomes more prevalent in modern society, family- and school-based sleep interventions that aim to enhance sleep hygiene and increase sleep duration may have important public health implications for the prevention and intervention of obesity and type 2 diabetes in children, the authors concluded.

"Furthermore, our results demonstrate an important relationship between REM sleep and high BMI and obesity, suggesting that the short sleep-obesity association may be attributed to reduced REM sleep time and decreased activity during REM sleep," they wrote.

The study was published in the August issue of the Archives of General Psychiatry.

SOURCE: JAMA/Archives journals, news release, Aug. 4, 2008