Sleep Affects Your Appetite in the Same Way as Marijuana, eLife
Sleep deprivation has long been known to make people crave higher-calorie foods. In a recent study led by Thorsten Kahnt, a neurologist at Northwestern Feinberg School of Medicine, researchers established links between sleep, the endocannabinoid system, smell, and appetite in humans. Their conclusion was stunning: sleep loss influences the same smell-processing neural pathway that smoking marijuana does.
The team asked 25 healthy volunteers to sleep for either 4 hours or 8 hours per night for four weeks, and then switch their sleeping patterns for another 4 weeks. Blood samples were taken from the volunteers. Sleep-deprived volunteers, as expected, had higher levels of 2-oleoylglycerol, a molecule that likely acts on endocannabinoid receptors. However, the sleep-deprived volunteers did not report feeling hungrier than their well-rested fellows, and both groups consumed the same average amount of calories. However, people in the sleep-deprived group consistently chose foods that packed more energy per gram—for example, glazed doughnuts instead of blueberry muffins.
Then the team took MRI scans of the volunteers while they were smelling different kinds of food. The researchers found that sleep-deprived participants’ piriform cortices, which are responsible for interpreting smells, showed increased activity in response to food-related smells, but not in a way that directly correlated with their changes in appetite. When researchers looked at information flow between the insula, a region deep inside the brain that helps regulate food intake, and the piriform cortex, they found that volunteers with higher levels of 2-oleoylglycerol showed consistently less “chatter” between the two regions. A pathway by which the olfactory system and food intake were affected by a lack of sleep was developed by the team and published recently on eLife.
Though the cause-effect relationship between the two regions in the brain is still unclear, the work solidifies the connection between sleep deprivation, sensory processes, and appetite. “It also really underscores the role that the sense of smell has in guiding food choices,” says Kahnt. Kahnt and his team are also going to further investigate the effect of the time of awakening and extended fasting. Poor volunteers.