Campus researchers find correlation between bedtime, weight gain

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UC Berkeley researchers have conducted a study that suggests teens and adults who go to bed late at night tend to gain weight more easily even when they sleep more hours.

In the study, published in the October edition of the journal Sleep, UC Berkeley researchers examined sleep data,  collected between 1996 and 2009, from a national database of more than 3,000 adolescents and adults. Researchers found that the relationship between late nights and weight gain went beyond what was typical of developmental changes that occur between adolescence and adulthood.

The study drew from previous data contributing to what it described as a “serious epidemic” of insufficient sleep among adolescents. According to the report, between 45 percent and 80 percent of adolescents experience insufficient sleep on school nights. More than 60 percent of young adults between the ages of 18 and 24 went to bed after 11 p.m.

UC Berkeley doctoral student in clinical psychology Lauren Asarnow, the lead author for the research, recommends that students get at least nine hours of sleep per night.

Asarnow said her research suggested that a woman of average height — about 5-foot-5 — and weighing 132 pounds who goes to bed late during the period from adolescence to adulthood could gain about 12 additional pounds or two body mass index units over that period of time.

“This was true regardless of how much sleep you were getting,” Asarnow said. “Going to bed at 2 a.m., even if you are getting eight hours of sleep and waking up at 10 a.m., is still associated with weight gain.”

Asarnow said that she sees the result as potentially very good news because bedtime is a highly modifiable behavior and that the next step for researchers is to further study how adjusting bedtime affects weight.

ASUC Academic Affairs Vice President Melissa Hsu said that while she wouldn’t change her sleeping habits after learning about the study, students should go to bed earlier. Hsu, who has advocated relaxation spaces on campus, said students should keep in mind the consequences that sleep deprivation can have on mental health.

After reading about the study, John Swartzberg, a professor emeritus in the campus School of Public Health, said in an email that the research was “solid” but that an association between bedtime and weight gain does not necessarily prove one causes the other.

Subjects in the study self-reported their bedtime and sleep hours, and researchers calculated their BMI based on weight and height.

Allison Harvey, a senior author of the study and director of the campus’s Golden Bear Sleep and Mood Research Clinic, is researching whether changing sleep has effects on weight gain and eating behavior, as well as emotional health and academic performance, according to Asarnow.

Contact Danwei Ma at [email protected].