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UNIVERSITY PARK, Pa. — Have you been noticing you're not quite as satisfied as you used to be after a big meal? According to a new study, your sleeping habits may be to blame for feeling hungry more frequently. Researchers at Penn State University say not getting enough sleep for just a few days can change how one's metabolism operates and cause us to feel less full after eating.
From an evolutionary perspective, a lack of sleep signals to our bodies that we're dealing with some type of problem (predators, unsafe environment, etc.). In response, our metabolism slows, encouraging us to eat more than we really need so we have additional energy to cope with said problem.
“While this was a good mechanism in evolutionary terms, to store energy for tough times, it’s not so good in today’s developed world where we are relatively inactive and calorie-dense foods are easy to come by cheaply and without physical effort,” explains professor Orfeu Buxton, a senior author on the study, in a release.
In the past, Buxton had led additional research linking sleep loss to increased risk of obesity, but those studies focused on glucose metabolism. This study, on the other hand, is among the first to hone in on lipid digestion from food.
For the study, 15 healthy men in their 20s spent 10 nights getting plenty of sleep from the comfort of their homes. Then, each participant spent 10 nights sleeping in the researchers' “sleep lab.” During four consecutive nights spent in the lab, participants only slept for five hours. Each man was also fed a high fat, high calorie diet of pasta and chili while staying in the lab.
“Most of the participants reported they felt less satisfied after eating the same meal while sleep-deprived, than when they had eaten it well-rested,” comments Kelly Ness, a postdoctoral fellow at the University of Washington. Ness ran the experiment while she was graduate student at Penn State.
“Across a lifetime of exposure to short sleep, this could increase the risk of obesity, diabetes or other metabolic diseases,” Ness adds.
Blood samples taken from participants while they were eating also revealed that lack of sleep led to higher insulin levels and a faster clearance of lipids from the blood. These developments make it much easier to gain weight; the lipids aren't just disappearing, they are being stored.
The experiment concluded by having participants sleep for 10 hours on two consecutive nights. This was intended to simulate a weekend of catching up on sleep. Interestingly, while participants' metabolic processing of fat was slightly faster after getting some more sleep, their metabolisms still failed to bounce back to their baseline readings. Although it is worth mentioning that participants' weights did return to normal after just two days of improved sleep.
Researchers say this suggests that complex metabolic shifts occur in our bodies after a period of restricted sleep, the extent of which we don't fully understand yet.
“The primary problem in obesity is how fat tissue functions to store fat energy,” says associate professor Greg Shearer. “By storing fats quickly, fat tissues appear to shift fuel utilization away from fats and prioritize the use of sugars for fuel. Here we show evidence that sleep restriction exaggerates this process, conserving energy stores.”
In the future, the research team would like additional experiments to be conducted on the matter. Ideally, these studies would include a broader experimental group and allow for extended recovery times.
The study is published in The Journal of Lipid Research.
