Watch Now: Late Bedtimes Linked to Weight Gain

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October 13, 2015


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If you’re hoping to avoid weight gain, here’s one fattening recipe to skip: a late bedtime. Teen and adults with late bedtimes on weeknights are more likely to put on pounds than those who go to sleep earlier, according to new research from the University of California, Berkley.

The research team detected a link between body mass index (BMI) and bedtimes. The new research appears in the October issue of Sleep, a medical journal jointly published by the Sleep Research Society and the American Academy of Sleep Medicine.

The study involved more than 3,300 teens and adults nationwide, and the analysis shows that every lost hour of sleep translated into a gain of 2.1 BMI points during a five-year period. What’s more, the spike in BMI was not mitigated by other factors such as exercise, screen time or total amount of hours slept.

“These results highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management during the transition to adulthood,” says Lauren Asarnow, who is the lead author of the study and a doctoral student in UC Berkeley’s Golden Bear Sleep and Mood Research Clinic.

Lack of sleep carries other risks, and there could be a connection between your sleepless nights and expanding waistline, according to Timothy Grant, M.D., medical director of Baptist Sleep Center at Sunset.

“Sleep deprivation causes havoc on your internal clock and puts you at risk for chronic illnesses, including heart disease and diabetes,” Dr. Grant says.

Lack of sleep upsets the normal activities of two hormones that control our appetite. Leptin is the hormone that sends the “stomach-is-full” message to the brain, and ghrelin is the hormone that sends out “eat-more” messages. But when you’re starved for sleep, those appetite-controlling hormones are thrown off balance.

What is BMI?

BMI is a calculation based on your height and weight. A BMI between 18.5 and 24.9 is considered healthy weight. Someone with a BMI in the 25-to-29.9 range is considered overweight, and a BMI over 30 qualifies a person as obese.

Bedtime Study Methodology

The Berkeley research team analyzed data from the National Longitudinal Study of Adolescent Health, an ongoing research project that has tracked the behaviors of teens in the U.S. since 1994. With that data, the Berkeley research team compared BMI and bedtimes for teens from 1994 through 2009.

The research focused on three key milestones:
• Onset of puberty.
• College years.
• Young adult years.

Teens in the study provided their bedtimes and the amount of sleep they received on a nightly basis. Researchers made the BMI calculations for each subject based on height and weight data. The conclusion: Teens with an earlier bedtime set up a “healthier course” for weight management as they become adults, according to Asarnow.

A good night’s sleep offers other perks, according to past research.

“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,” according to a news release from the University of California, Berkeley.

(Watch the video below to learn more about sleep and weight gain from Timothy Grant, M.D., medical director of Baptist Sleep Center at Sunset. Dr. Grant spoke at a Community Health event.)

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