Prolonged stints of limited sleep and late bedtimes may play a role in weight gain, says a new sleep study out of the University of Pennsylvania. Researchers report that late-night eating is likely the culprit.
“When sleep is restricted because individuals delay their bedtime, our study shows that individuals will consume a substantial amount of calories during these additional waking hours late at night,” said lead author Andrea Spaeth, a doctoral candidate in the University of Pennsylvania’s psychology department.
According to Spaeth, subjects who followed this pattern actually consumed an average of 100 fewer calories the next morning. Even so, it wasn’t enough to offset the additional 550 calories consumed the night before.
“Therefore, one could imagine that over time, those with short sleep duration and delayed bedtimes are shifting the majority of their caloric intake to evening/late-night hours rather than consuming the majority of calories during morning/afternoon hours,” said Spaeth.
These findings suggest that sleep restriction causes weight gain by not only increasing overall daily caloric intake, but by disrupting the timing of caloric intake. The study consisted of 225 healthy, non-obese adults aged 22 to 50 who spent up to 18 consecutive days in the lab. Participants were provided with food and asked to refrain from exercising for the duration of the study. During this time, some stayed in bed for 10 hours each night, while others were restricted to just four hours of sleep from 4 a.m. to 8 a.m.
“We found the race and gender differences in weight gain particularly interesting,” said Spaeth, who noted that males gained more weight than females.
Additionally, African Americans gained more weight than Caucasians.
“Thus, African American males were particularly vulnerable to the weight-gain effects of sleep restriction, whereas Caucasian females were relatively resistant.”
Spaeth and her team are currently examining race and gender differences in food intake and timing to better understand the behavioral and physiological mechanisms that might underlie these differences.
By Marianne Hayes