A recent study out of the University of Pennsylvania, Philadelphia found that those who got only four hours of sleep per night were more likely to gain weight after only five days of sleep deprivation compared to those who slept normally.
This wasn't a small study, either. In fact, it was one of the largest studies in terms of the number of participants and participant diversity to investigate sleep's effect on weight, calorie intake and meal timing.
The study involved 225 healthy individuals aged between 22 and 50. All were non-smokers, and reported no problems with sleep in the 60 days prior to the study.
Those in the control group spent 10 hours per day in bed (from 10 pm to 8 am). Those in the sleep restriction group were given 10-12 hours in bed for 2 days, then their sleep was restricted to just 4 hours (from 4 am to 8 am) for the next 5 nights.
Those in the sleep restriction group gained about 1 kg (2.2 lbs). In contrast, those in the control group gained only around a tenth of that weight (all participants were confined to a laboratory for the duration of the study).
So why the weight gain? Researchers argue it's down to late night eating and eating meals with higher fat content.
In fact, they monitored a subset of the sleep restriction group and the control group's food and drink consumption (but still let them eat and drink what they liked). Those in the sleep restriction group who knew their intake was being monitored gained slightly less weight (about 1/2 kg) whilst those in the control group actually lost 1/2 kg.
Also of interest, sleep deprived men tended to gain more weight than women and black participants gained more weight when sleep deprived compared to white participants.
In conclusion, it seems that sleep deprivation makes us gain weight because when we're sleep deprived we eat less healthily. As for why that may be the case, we probably need more research to say definitively.
Last updated: October 1, 2013