Late bedtimes could lead to weight gain

http://www.eurekalert.org/pub_releases/2015-10/uoc--lbc100115.php

Public Release: 1-Oct-2015
Late bedtimes could lead to weight gain
Teen night owls may want to hit the hay earlier, study suggests
University of California - Berkeley

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 from the University of California, Berkeley, that has found a correlation between sleep and body mass index.

Berkeley researchers analyzed longitudinal data from a nationally representative cohort of more than 3,300 youths and adults, 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 October issue of the journal, Sleep.

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Surveys show that many teenagers do not get the recommended nine hours sleep a night, and report having trouble staying awake at school. The human circadian rhythm, which regulates physiological and metabolic functions, typically shifts to a later sleep cycle at the onset of puberty.

The results 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.