*The following is excerpted from an online article from PsychCentral.
A new study has discovered a link between staying up late at night and having a higher body mass index (BMI) in teenagers.
Specifically, the findings show that teens who go to bed late on weeknights are more likely to gain weight compared to those who go to sleep earlier. This late-bedtime link remained consistent regardless of how many hours the teens actually slept.
Researchers from the University of California, Berkeley, analyzed longitudinal data from a national sample group of more than 3,300 youths and adults, and found that for every extra hour they stayed awake, they gained 2.1 points on the BMI index. This gain occurred roughly over a five-year period.
Furthermore, exercise, screen time, and the number of hours they slept did not affect this BMI increase.
"These results highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management during the transition to adulthood," said Lauren Asarnow, lead author of the study and a doctoral student in University of California, Berkeley’s Golden Bear Sleep and Mood Research Clinic.
The Berkeley study analyzed data from the National Longitudinal Study of Adolescent Health, which has tracked the influences and behaviors of U.S. teenagers since 1994. Focusing on three time periods — the onset of puberty, the college-age years and young adulthood — researchers compared the bedtimes and BMI of teens from 1994 to 2009.
The findings of the study thus suggest that adolescents who go to bed earlier will "set their weight on a healthier course as they emerge into adulthood," Asarnow said.
The research is published in the journal Sleep.
Source: PsychCentral
http://psychcentral.com/news/2015/10/05/late-bedtime-linked-to-weight-gain-in-teens/93029.html