The more fatigue accumulates, the more our desire to junk foodgrows. But why do nights that are too short push us to rush for the first burger that comes along? Neuroscience researchers from the universities of Chicago (United States) and Brussels (Belgium) asked themselves the question, and found a biological answer. Sleep deprivation would indeed be associated with the activation of the endocannabinoid nervous system, which plays a key role in the reward circuits involving variations in appetite and food intake. Their study, published in the journal sleeping, compared the state of the endocannabinoid system in 14 healthy adults. These people first slept four normal nights of 8.5 hours, then four short nights of 4.5 hours. At the end of these two periods, the researchers made several foods available to them. Result: When they were sleep deprived, the participants had difficulty resisting attractive snacks such as chips, cakes and candies, even if, two hours before, they had consumed meals filling 90% of their daily caloric intake. In this situation, not only did the subjects find it difficult to restrict their consumption of snacks, but in addition, the food chosen contained up to twice as much fat as the one they preferred when they had had enough sleep.
More pleasure when eating
“We found that sleep deprivation boosts a signal that can increase hedonicity of food intake, pleasure and satisfaction from eating“explains Dr. Erin Hanlon, co-author of the study, in a press release from the American Association for the Advancement of Science (AAAS). “Lack of sleep seems to stimulate the endocannabinoid system, the one that is for example targeted by the active substance in marijuana, to increase the desire for food intake” she specifies. When the nights are long enough, the endocannabinoid signal is weak during the night, increases in the morning until a peak in the middle of the day and decreases in the afternoon. Conversely, when the nights are too short, the signal remains high until late afternoon up to 33% more than the normal level without sleep deprivation.
Lack of sleep and obesity
These high levels would be responsible for a greater desire for food, and in particular fatty food because fatigue could alter our will. “If you have a Snickers, and you have had enough sleep, you can control your natural urge. But if you are sleep-deprived, your hedonistic attraction to this food becomes stronger, and your ability to resist it may be diminished. You are then more likely to eat it. Repeat that, and you gain weight“, details Erin Hanlon. Thus, this mechanism could explain why lack of sleep is often associated with the risk of obesityby promoting additional food intake in the afternoon and early evening.
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