Individuals who experience chronic lack of sleep are at greater risk of becoming overweight and obese, in part because sleep deprivation leads to eating more, making unhealthy food choices and craving high-calorie foods.
In a new study, researchers at Uppsala University investigated how levels of endocannabinoids — which target the same receptors as cannabis — are affected by lack of sleep, and whether acute exercise can modulate this effect. They found instead that exercise tends to increase hunger, even in sleep deprivation, potentially due to its ability to reduce stress.
“Previous studies have shown alterations in the levels of some hunger hormones after sleep loss, but the results have been mixed and hormones that drive hedonic food intake have been less investigated,” says lead author of the new study Jonathan Cedernaes, M.D., Ph.D, at Uppsala University.
“Furthermore, whereas exercise has many beneficial effects, whether exercise can modulate the effects of sleep loss on various hormonal pathways is currently unknown.”
For the study, healthy normal-weight participants stayed in a sleep laboratory on two separate occasions. They were studied after three consecutive nights of normal sleep and after three nights of only sleeping four hours each night. Meals and activity patterns were kept standardized while participants were in the lab, and blood was drawn several times to measure endocannabinoid levels in blood. This was also done on the last day both before and after a short bout of intensive exercise.
The researchers found that the levels of 2-arachidonoylglycerol (2AG) — the most abundant endocannabinoid in the brain — was about 80 percent higher after the nights of short sleep compared with after the normal sleep session. When the participants exercised, the levels of 2AG still went up almost by half, regardless of whether participants had gotten three nights of plenty of sleep or only four hours of sleep each night.
“As previously shown by us and others, sleep loss increased subjective hunger compared with the well-rested state,” said senior author associate professor Christian Benedict. “Given the role of endocannabinoids for promoting hunger and hedonic eating, this could offer an explanation as to why.”
“Meanwhile, we instead saw lower stress ratings after exercise in the sleep deprivation condition, which could also possibly be attributed to the observed endocannabinoid levels following our exercise intervention.”
So even when sleep-deprived, the participants experienced the same amount of increase in endocannabinoid levels just after exercising.
“Endocannabinoids are thought to confer both the “runner’s high” as well as at least some of the neuroprotective effects of exercise. Therefore, this may suggest that even under conditions of chronic sleep loss, exercise may exert similar centrally active, and possibly neuroprotective, properties as under conditions of sufficient sleep,” said Cedernaes.
“This is an important area for future research as we and others have found that short sleep duration by itself may be harmful to the brain, and in the long run increase the risk of e.g. Alzheimer’s disease.”
The findings are published in the journal Psychoneuroendocrinology.
Source: Uppsala University