The more fatigue accumulates, the more our desire to junk foodgrows. But why do nights that are too short lead us to rush for the first burger we come across? Neuroscience researchers from the universities of Chicago (United States) and Brussels (Belgium) asked themselves the question, and found a biological answer to it. Sleep deprivation is in fact 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 Sleep, compared the state of the endocannabinoid system in 14 healthy adults. These people first slept four normal 8.5-hour nights, then four short 4.5-hour nights. At the end of these two periods, the researchers made several foods available to them. As a result, when they were sleep deprived, participants found it difficult to resist appealing snacks such as chips, cakes and candies, even though, two hours earlier, they had consumed meals that met 90% of their daily calorie intake. In this situation, not only did the subjects find it difficult to restrict their snack intake, but the food they chose contained up to twice as much fat as what they preferred when they had enough sleep.
More pleasure when eating
“We have found that sleep deprivation boosts a signal that can increase the hedonicity of food intake, the pleasure and satisfaction of eating.“said Dr. Erin Hanlon, co-author of the study, in a statement from the American Association for the Advancement of Science (AAAS). “Lack of sleep seems to stimulate the endocannabinoid system, the one targeted by the active substance in marijuana, for example, to increase the desire for food intake.When the nights are long enough, the endocannabinoid signal is weak during the night, increases in the morning to 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 the end of the 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 for fatty food because fatigue could impair our will. “If you have a Snickers, and that 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 then have a better chance of eating it. Repeat this, and you gain weight“, details Erin Hanlon. Thus, this mechanism could explain why lack of sleep is often associated with the risk of obesity, by promoting additional food intake in the afternoon and early evening.
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