Lack of sleep affects fat metabolism, study says

A few days of sleep deprivation can make individuals feel less full after eating and metabolize the fat in food differently, according to a new study by researchers at Pennsylvania State University, which was published in the Journal of Lipid Research.

For the study, 15 healthy male participants in their 20s spent one week getting plenty of sleep at home. They then checked into a sleep lab for ten nights. For five of those nights, the participants spent no more than five hours in bed each night. Researchers collected data but also spent time interacting with the participants, playing games with them, talking with them, and helping to keep them awake and engaged.

To find out how the uncomfortable schedule affected metabolism, the researchers gave participants a standardized high-fat dinner, a bowl of chili mac, after four nights of sleep restriction. Then researchers compared blood samples from the study participants. They found that sleep restriction affected the postprandial lipid response, leading to faster clearance of lipids from the blood after a meal. That could predispose people to put on weight. 

The simulated workweek ended with a simulated Friday and Saturday night when participants could spend ten hours in bed catching up on missed sleep. After the first night, they ate one last bowl of chili mac. Although participants' metabolic handling of fat from food was slightly better after a night of recovery sleep, they didn't recover to the baseline healthy level.

This study was highly controlled, which makes it an imperfect model for the real world, according to Kelly Ness, PhD, postdoctoral fellow at the University of Washington who ran the study as a graduate student under the direction of Orfeu Buxton, PhD, a professor at Penn State and one of the senior authors. The research focused on healthy young people, who are usually at a lower risk of cardiovascular disease, and all the participants were men. The researchers also said they wondered whether giving more recovery time would change the magnitude of recovery they observed.

Regardless, Buxton said the study gives worthwhile insights into how humans handle fat digestion.

"This study's importance relies on its translational relevance,” Buxton said in a statement. “A high-fat meal in the evening, at dinnertime, and real food, not something infused into the vein? That's a typical exposure. That's very American."