Going to bed late on weeknights is linked to an increase in body mass index (BMI) over time, new information claims. Researchers from the University of California Berkeley said teenagers who stay up late are more likely to gain weight, Health Day reported.
To determine the association between bed times and BMI, the researchers studied data from 3,342 teenagers. They found that every hour of sleep lost by staying up late resulted in a 2.1-point increase in BMI over a period of five years.
"Conceivably, if you're going to bed an hour later, over time you could be shifting BMI categories from normal to overweight," lead study author Lauren Asarnow, doctoral student at the Golden Bear Sleep and Mood Research Clinic at UC Berkeley, told CBS News. "So even a two-point increase could be clinically significant."
Interestingly, this relationship between late bedtimes and BMI increase was not affected by sleeping late, increasing total sleep time or doing exercises. This means weight management for teens can be controlled by having an earlier bedtime.
"These results highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management during the transition to adulthood," Asarnow said in a press release.
Asarnow had two theories as to why late bedtimes lead to weight gain.
"If you're staying up late you're more likely to be eating junk food late at night," she said. "People who stay up late are also less likely to eat breakfast and breakfast skipping is associated with weight gain."
She noted that adolescents who modify their sleeping time will have a greater chance of keeping the pounds off.
"If you could shift bedtime in the teenage years, you can create good sleep habits and maybe prevent weight gain over time," she said.
The study was published in the October issue of the journal Sleep.
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