Late bedtimes could lead to weight gain

Teenagers and adults who go to bed late on weeknights are more likely to gain weight than their peers who hit the hay earlier, according to a new study.
Researchers from the University of California, Berkeley, found a correlation between sleep and body mass index (BMI).
The researchers analysed longitudinal data from a nationally representative cohort of more than 3,300 youths and adults in the US, and found that for every hour of sleep they lost, they gained 2.1 points on the BMI index. This gain occurred roughly over a five-year period.
Moreover, exercise, screen time, and the number of hours they slept did not mitigate this BMI increase, according to the study published in the journal Sleep.

"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 UC Berkeley's Golden Bear Sleep and Mood Research Clinic.
The study analysed data from the National Longitudinal Study of Adolescent Health, which has tracked the influences and behaviours of US 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 teenagers from 1994 to 2009.
Adolescents in the study reported their bedtimes and sleep hours while researchers calculated their BMI based on their height and weight.

The results of the study suggested that adolescents who go to bed earlier will "set their weight on a healthier course as they emerge into adulthood," Asarnow said.