New York, Oct 2 (IANS): If your teenage kid loves to spend night time with gadgets, ask him or her to reduce this habit as this may make him fat in just five years' time.

According to research, teenagers and adults who go to bed late on weeknights are more likely to gain weight than their peers who hit the hay earlier.

"The results highlight adolescent bed times, not just total sleep time, as a potential target for weight management during the transition to adulthood," said Lauren Asarnow, lead author and doctoral student in University of California-Berkeley.

For this, the researchers analysed data from a nationally representative cohort of more than 3,300 youths and adults.

They found that for every hour of sleep they lost, they gained 2.1 points on the body mass index (BMI). This gain occurred roughly over a five-year period.

The results 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 suggest that adolescents who go to bed earlier will "set their weight on a healthier course as they emerge into adulthood", Asarnow added.

The paper appeared in the journal Sleep.