NEW studies are shedding light on why people eat unhealthier food and more of it when they do not get enough sleep.
A small study published in the journal Sleep earlier in March 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 was 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 Centre 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 had found lack of sleep led to decreases in the hormone leptin, which inhibited hunger, and increases in ghrelin, which induced hunger, said Frank Scheer, director of the Medical Chronobiology Programme at Brigham and Women’s Hospital in Boston.
Although studies had found that being awake longer naturally led to increased energy expenditure and a need for more food intake, the overeating that typically took place in people who were sleep-deprived exceeded 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 were sleep-deprived would gain weight even if they ate the same food as when they were getting a full night’s sleep remained 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 Centre at the University of Chicago and senior author of the Sleep study, noted that the study demonstrated that circulating levels of 2-AG varied enormously throughout the day, with very low levels during the night and a sharp increase from morning to afternoon — an effect that was 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 programmes, some researchers say a randomised 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 were looking at whether extending sleep by 1.5 hours a day in overweight adults would 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 eight 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 Centre, 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 centres. The findings, published in the American Journal of Clinical Nutrition in 2012, dovetailed 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 fibre 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 (affect) 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.
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Picture: THINKSTOCK
NEW studies are shedding light on why people eat unhealthier food and more of it when they do not get enough sleep.
A small study published in the journal Sleep earlier in March 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 was 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 Centre 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 had found lack of sleep led to decreases in the hormone leptin, which inhibited hunger, and increases in ghrelin, which induced hunger, said Frank Scheer, director of the Medical Chronobiology Programme at Brigham and Women’s Hospital in Boston.
Although studies had found that being awake longer naturally led to increased energy expenditure and a need for more food intake, the overeating that typically took place in people who were sleep-deprived exceeded 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 were sleep-deprived would gain weight even if they ate the same food as when they were getting a full night’s sleep remained 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 Centre at the University of Chicago and senior author of the Sleep study, noted that the study demonstrated that circulating levels of 2-AG varied enormously throughout the day, with very low levels during the night and a sharp increase from morning to afternoon — an effect that was 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 programmes, some researchers say a randomised 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 were looking at whether extending sleep by 1.5 hours a day in overweight adults would 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 eight 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 Centre, 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 centres. The findings, published in the American Journal of Clinical Nutrition in 2012, dovetailed 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 fibre 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 (affect) 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.
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