Sleep late, gain weight
A new study shows that sleeping late will make you gain weight. Researchers found that every hour of sleep less than the nine-hour ideal lead to gaining 2.1 points on BMI Index in the span of five years.
University of California, Berkeley researchers analyzed longitudinal data from a nationally representative cohort of more than 3,300 youths and adults.
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,” said Lauren Asarnow, lead author of the study and a doctoral student in UC Berkeley’s Golden Bear Sleep and Mood Research Clinic.
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.
“These results highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management during the transition to adulthood,” said Asarnow.
BMI is the measure of a person’s weight in kilograms divided by the square of height in meters. A healthy adult BMI range is estimated to be 18.5 to 24.9.
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 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.
