Why We Eat Too Much When We Don’t Sleep Enough.

Researchers study why getting too little sleep leads us to snack more the next day, not only eating more but eating more unhealthy foods

New studies are shedding light on why people eat unhealthier food and more of it when they don’t get enough sleep.

A small study published in the journal Sleep earlier this month found a new mechanism that helps explain why people who are sleep-deprived are at greater risk of gaining weight. University of Chicago researchers found that 14 individuals who were sleep-deprived consumed nearly 1,000 calories in snacks in the early evening compared with 600 calories when they had a full night’s sleep, and when they were sleep-deprived they ate twice as much fat. Calories consumed at a lunch time buffet remained the same.

The conclusion was that when deprived of sleep, the individuals had a greater activation of the endocannabinoid system, which is involved in reward-driven or pleasurable eating, said Erin Hanlon, first author of the study and a research associate at the Sleep Metabolism and Health Center at the University of Chicago.

The endocannabinoid system—composed of lipids that are produced somewhere in the body and that can be measured in the blood—is also triggered in people who smoke marijuana and is thought to be the source of the so-called munchies.

The individuals, sleeping in a laboratory, had four nights of 8.5 hours of sleep and four nights of 4.5 hours. Their average levels of the endocannabinoid 2-AG were the same over 24 hours following both the 8.5 hours and the 4.5 hours of sleep, but peak levels were higher and occurred later in the day in the shorter sleep condition.

“They reported feeling hungrier and having a stronger desire to eat, which corresponds to the same time of day where we see this increase in endocannabinoid levels,” said Dr. Hanlon.

“We certainly don’t think the endocannabinoid system and activation of it is the only contributing factor to overeating following sleep restriction, Dr. Hanlon said. “But we do think that it could be a contributing factor.”

Previous studies have found lack of sleep leads to decreases in the hormone leptin, which inhibits hunger, and increases in ghrelin, which induces hunger, said Frank Scheer, director of the Medical Chronobiology Program at Brigham and Women’s Hospital in Boston.

Though studies have found that being awake longer naturally leads to increased energy expenditure and a need for more food intake, the overeating that typically takes place in people who are sleep-deprived exceeds increases in energy expenditure, resulting in weight gain, said Dr. Scheer, who wrote an editorial about the study in the same issue of Sleep.

The question of whether people who are sleep-deprived would gain weight even if they ate the same food as when they were getting a full night’s sleep remains unknown, Dr. Scheer said. The mechanism for weight gain may be primarily via increased food intake.

He pointed to a study that touched on that question, published in 2010 in the Annals of Internal Medicine. It found individuals who were on a diet lost less fat mass and more lean body mass when they were sleep-deprived.

Andrea Spaeth, a post-doctoral fellow at the University of Pennsylvania Perelman School of Medicine, published a study last year in the journal Obesity, where she and colleagues found that the resting metabolic rate was lower in individuals the morning after five nights of sleep restriction compared with after a normal night’s sleep.

“The next day you’re burning fewer calories at rest than you would if you weren’t sleep-restricted,” she said, noting it was about 42 calories less. “Over time that could accumulate.”

Eve Van Cauter, director of the Sleep, Metabolism and Health Center at the University of Chicago and senior author of the Sleep study, noted that the study demonstrated that circulating levels of 2-AG vary enormously throughout the day, with very low levels during the night and a sharp increase from morning to afternoon—an effect that is prolonged and enhanced by sleep restriction.

“This stimulation of the endocannabinoid system may explain why people who are sleep-restricted tend to eat more snacks rather than eat larger meals,” she said. “It’s more like they just grab anything that’s around them.”

Her research has found that sleep-deprived individuals crave salty food the most, followed by sweet and then starchy foods.

Another unexplored question is how sleep quality affects food intake. Studies have found that when individuals get less deep or slow-wave sleep, their glucose tolerance decreases, which increases the risk of developing Type 2 diabetes.

Before nutritionists and clinicians can start incorporating sleep recommendations into weight-loss programs, some researchers say a randomized controlled study would need to prove that extending sleep helps lead to weight loss.

University of Chicago researchers are currently in the second year of such a federally funded study. They are looking at whether extending sleep by 1.5 hours a day in overweight adults will lead to changes in energy balance and ultimately to weight loss, said Esra Tasali, an associate professor of medicine at the University of Chicago and principal investigator of that study.

The researchers are measuring the sleep of people who normally sleep 6.5 hours or less a night and asking them to sleep 7.5 to 8 hours—the amount recommended by sleep professionals. They are giving the participants devices to bring home that will capture their sleep patterns and energy expenditures. The researchers are currently recruiting up to 80 overweight individuals for the five-year study.

Marie-Pierre St-Onge, an assistant professor of medicine at Columbia University Medical Center, has done neuroimaging studies on 27 people comparing their neural responses to food images when sleep-restricted to when they get a full night’s sleep. She found that when sleep-restricted, the individuals had a greater neural response in the brain regions involved in reward centers. The findings, published in the American Journal of Clinical Nutrition in 2012, dovetail well with the recent endocannabinoid study, she said.

More recently Dr. St-Onge did a secondary analysis of the data from her 2012 study and also found what we eat may affect sleep quality. When individuals were allowed to eat what they wanted, those who ate more fiber had more slow-wave sleep, whereas those with a higher saturated fat intake had less slow-wave sleep. Additionally, a greater sugar intake was associated with more arousals in the middle of the night. The findings were published in January in the Journal of Clinical Sleep Medicine.

“It’s important to note that what you eat during the day can impact how you sleep,” she said. “It’s sort of a vicious cycle. Your sleep at night influences your appetite and food choices during the day” and vice versa, she said.