Snoozing Really Is Losing: Late Sleepers Pack on More Pounds

If you are the late night type, then be prepared for an increase in body mass index (BMI) over time. Teenagers who hit the sack late are more likely to gain weight, researchers from the University of California Berkeley said.

To study the link between bed times and BMI, researchers examined 3,342 teenagers. They found that for every hour of sleep lost by staying up late, they gained a 2.1-point increase in BMI over 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 said, according to CBS News.  "So even a two-point increase could be clinically significant."

Moreover, the link between late bedtimes and BMI increase was not affected by sleeping late, increasing total sleep time or doing exercises. Hence, teenagers can manage weight by sleeping earlier.

"These results highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management during the transition to adulthood," Asarnow said.

"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 also noted that adolescents who push back their sleeping time can help to reduce weight.

"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.