Study Links Late Bedtime to Weight Gain in Healthy Adults

A new study highlights the ill-effects of staying up late in the night. The study suggests that healthy adults with late bedtimes are more likely to gain weight because of the food they snack on.

Researchers at the Perelman School of Medicine at the University of Pennsylvania have found that healthy adults with late bedtimes and chronic sleep limitation may be more prone to gain weight due to an increased intake of calories during the late night hours. This is the largest, diverse sample of healthy adults studied till date under controlled laboratory conditions.

"A number of epidemiological studies have found an association between short sleep duration and weight gain, and ultimately obesity," said senior study author Namni Goel, PhD, research associate professor of Psychology in Psychiatry, Division of Sleep and Chronobiology at Penn. "We wanted to examine this in a controlled experimental study to determine whether we would observe weight gain over a short period of time when subjects were sleep-restricted. We also sought to determine the source of such weight gain--that is, whether it was due to an additional intake of calories beyond what was needed to maintain body weight."

The study conducted at Sleep and Chronobiology Laboratory at the Hospital of the University of Pennsylvania consisted of 225 healthy individuals who were not obese. They belonged to the age group 22-50 years. The subjects in the study were randomly divided into two different groups.  Those in the first group were subjected to restricted sleep and the second group participants were the control group. The participants spent 18 consecutive days in the laboratory.

The participants were served food at meal times and apart from that, food was also easily available in the laboratory kitchen for those who wanted to eat at other times of day. They were not permitted to do any exercise but could watch T.V., play video games, read and perform other sedentary activities.

They noticed that the participants in the sleep restricted group that spent just four hours in bed from 4 a.m. to 8 a.m. for five continuous nights gained weight when compared to the control participants that slept for 10 hours each night from 10 p.m. to 8 a.m..

Researchers observed that the first group that was subjected to restricted sleep put on more weight due to an increase in the number of meals taken during the additional hours the participants were awake. Most of the calories consumed were from the late night meals they consumed. They noticed that males were more likely to put on weight when compared to the females and African American gained more weight than Caucasians.

The American Academy of Sleep Medicine states that weight gain is a risk factor for OSA (Obstructive sleep apnea) that is a common sleep illness that affects the quality of life and has a great impact on health. The study was published in the journal SLEEP.