Sleep deprivation may cause overeating by boosting chemicals for appetite as well as those that increase the pleasure of eating sweet or salty, high-fat foods
The US-based researchers believe that missing-out on sleep alters brain chemicals in much the same way as the hunger-boosting chemicals found in cannabis, which for years has accounted for much of the snack sales in 24-hour convenience stores.
After several nights of limited sleep, healthy volunteers who took part in the study selected foods containing more calories, and almost twice as much fat, than subjects who slept well during the study.
Erin Hanlon, who led the study at the University of Chicago, reported that when sleep deprived, participants had difficulty resisting the snacks, even when they were full.
Research has shown repeatedly that sleep loss raises the risk of obesity, but the reasons are complex and unclear 1
Lack of sleep disrupts hormones that govern appetite and satiety. But those who sleep less have more time to eat, and may also be too tired to exercise. To confound matters further, obesity can lead to breathing problems which, in themselves, disrupt sleep patterns.
In a small-scale study published in the journal Sleep2 Hanlon invited 14 men and women in their twenties to spend two, four-day sessions, at Chicago University’s clinical research centre. The volunteers’ time in bed was controlled, so that on one visit they averaged 7.5 hours of sleep a night, but on the other only 4 hours 11 minutes. During all visits to the lab, the participants ate identical meals, served at 9am, 2pm and 7pm.
After the fourth night of each leg of the study, subjects were offered a range of snacks. The sleep-deprived participants felt a strong urge to binge on fatty foods, and this was most intense in the late afternoon and early evening, when snacking is most linked to weight gain. They consumed high-fat snacks even when they had eaten a solid meal containing 90% of their recommended daily calories only two hours earlier. Typically, the sleep deprived participants ate 300 calories in snacks, which is noteably in excess of energy requirements for their extra waking hours.
To explore just why sleep loss might trigger such changes in eating patterns, the researchers looked at various substances in the participants’ blood, including the hormones ghrelin, which boosts appetite, and leptin, which tells the brain when the stomach is full. Previous studies3 have shown that sleep loss tends to be reflected in high ghrelin and low leptin levels.
Hanlon also looked at levels of endocannabinoids and found that the sleep-deprived volunteers had raised and more persistent levels of endocannabinoid 2-AG, a chemical that increases the pleasure felt when eating (particularly sweet or salty high-fat foods). “We know that marijuana activates the endocannabinoid system and causes people to overeat when they are not hungry, and they normally eat yummy sweet and fatty foods,” Hanlon said. “Sleep restriction may cause overeating by acting in the same manner.”
In well-rested volunteers, levels of 2-AG rose in the morning, peaked around midday, and declined again. But in the sleep-deprived, levels rose 33% higher, peaked at 2pm, and remained high until 9pm. Writing in the journal, Hanlon posits that this may boost and prolong the pleasure people get from snacking, so putting them at greater risk of weight gain: “The early afternoon drive for hedonic eating may be stronger and last longer in a state of sleep debt.”
In a commentary published alongside Hanlon’s paper, Frank Scheer, director of medical chronobiology at Brigham and Women’s Hospital in Boston, says that the new findings make for “compelling evidence” that endocannabinoids and food reward mechanisms underpin the excessive eating and weight gain that comes with sleep loss.
1. Cappuccio FP, Taggart FM, Kandala NB, Currie A, Peile E, Stranges S, Miller MA.: Meta-analysis of short sleep duration and obesity in children and adults. SLEEP 2008; 31(5):619-26.
2. Bodez D, Guellich A, Kharoubi M, Covali-Noroc A, Tissot CM, Guendouz S, Hittinger L, Dubois-Randé JL, Lefaucheur JP, Planté-Bordeneuve V, Adnot S, Boyer L, Damy T.: Prevalence, severity, and prognostic value of sleep apnea syndromes in cardiac amyloidosis. SLEEP 2016; 39(7):1333–1341.
3. Klok MD, Jakobsdottir S, Drent ML.: The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obes Rev. 2007; 8(1):21-34.
Source: Amended from an original article by Ian Sample, Science editor, The Guardian, published Monday 29th February 2016