The more sleep you lose, the more weight you gain
In the largest, most diverse study on sleep restriction to date, researchers found that the more sleep people lost, the more weight they gained.
The study, published in the journal Sleep, involved 225 healthy test subjects who participated in a first-of-its-kind experiment conducted by sleep researchers from the Sleep and Chronobiology Laboratory at the Perelman School of Medicine at University of Pennsylvania.
The researchers discovered that when test subjects stayed up late, not going to bed until 4 a.m. and waking four hours later at 8 a.m., the number of calories they consumed after 11 p.m. was around 550, which is significantly more than their bodies needed.
Worse yet, the majority of the 550 calories they consumed came from fat; thus, causing them to gain an average of 2.2 pounds of weight after only five consecutive nights of restricted sleep.
Previous research has demonstrated similar results. However, this latest study is significant for two primary reasons: 1) it used a relatively large sample of 225 healthy people; and: 1) the research took place in a laboratory where researchers could control a variety of factors.
Andrea Spaeth, a doctoral candidate and the study’s lead author, said that the study’s test subjects could, for the most part, eat whenever they wanted and as much as they wanted. Meal sizes did not differ between the sleep-deprived group and a small control group.
“But [the deprived group] ate more times through the day and shifted their calorie intake toward late night,” Spaeth explained. “The next morning they’d actually eat less.”
There were also racial differences in the sleep-restricted test subjects. African-American men gained the most weight at an average of 3.7 pounds after five days, followed by African-American females and white men, with both groups gaining nearly 2.2 pounds. White women in the study, however, only gained an average of just under a pound.
“This is the first racial difference in such a study,” explained Kenneth Wright, associate professor in the department of integrative biology and the director of the Sleep and Chronobiology Laboratory at the University of Colorado, Boulder. “This provides experimental evidence for what we see in the epidemiological literature: that African-Americans seem to be more influenced by the effects of sleep loss.”
So why do people gain weight when their sleep is restricted? According to Wright, the answer remains somewhat mysterious.
In another experiment earlier this year, Wright’s lab also found that restricted sleep can cause you to eat more and gain weight.
The study, led by Wright and researchers from the University of Colorado Boulder, found that volunteers who got only 5 hours of sleep per night through the workweek, gained about 2 pounds when they had unlimited access to food.
“These findings provide evidence that sleep plays a key role in energy metabolism. Importantly, they demonstrate physiological and behavioral mechanisms by which insufficient sleep may contribute to overweight and obesity,” said the researchers.
Missing a night or two of sleep won’t necessarily make you gain weight, but consistently doing so during the week can.
"Just getting less sleep, by itself, is not going to lead to weight gain,” Wright said. “But when people get insufficient sleep, it leads them to eat more than actually need."
This explains, in part, why shift work can be so detrimental to health.
“Shift work goes against the fundamental biological clock in our brain. We evolved to be awake during the day when we are supposed to be physically active and consuming food. When we are awake at night, the circadian clock does not adapt. There are consequences to that,” Wright explained. “That’s why shift workers are at greater risk for many health problems we see in modern society.”
Because shift work isn’t going away, finding ways to compensate for this circadian havoc, and the toll it takes on the body, is a key goal of chronobiological research, according to Wright.
SOURCE: 1. SLEEP 2013 (Vol. 36, Issue 07: 981-990) Spaeth AM; Dinges DF; Goel N. “Effects of experimental sleep restriction on weight gain, caloric intake, and meal timing in healthy adults”. 2. Proceedings of the National Academy of Sciences (March 2013; DOI:10.1073/pnas.1216951110). Abstract, University of Boulder Colorado.