Lack of sleep stimulates the appetite and cravings for fatty foods. For the first time, researchers are linking this phenomenon to the endocannabinoid system.
Lack of sleep has long been associated with an unbalanced diet focused on fat and sugar. Until now, the underlying mechanisms had not been elucidated. But a team of researchers at the University of Chicago have discovered how sleep deprivation causes and amplifies the production of chemical appetite-stimulating signals, particularly the craving for junk food. They publish their results this monday in the newspaper Sleep.
Scientists studied 14 healthy young men and women in their 20s. After 4 sleepless nights, these participants could not resist cookies, candies and crisps. And this even after having eaten a gargantuan meal two hours before. This effect on appetite appears to be greater at the end of the day or early in the morning, times of the day when snacking promotes weight gain.
“Sleep deprivation appears to stimulate the endocannabinoid system – this is also the target of the active substances in cannabis – which induces gluttony, pleasure and the satisfaction of eating,” explains Erin Hanlon of the University of Chicago and lead author of the study.
Unusual variations
By taking blood samples from the volunteers, the researchers were able to isolate the responsible molecule: the endocannabinoid 2-arachidonoylglycerol (2-AG). Usually, the blood concentration of this molecule is low at night, then it increases during the day before reaching a peak in the late afternoon. But in volunteers lacking sleep, the level of 2-AG is higher during the day and remains high at night.
Moreover, it was during this period that participants reported greater appetite. And once at the table, they consumed twice as much fat as after a good night’s sleep.
For the authors, this increase in the level of endogenous endocannabinoid “could be the mechanism by which the lack of sleep leads to excessive food intake, in particular in the form of sugary snacks”. And by extension, it would partly explain why insomnia is linked to an increased risk of obesity and diabetes.
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