Scientists have chalked this up to simple energy needs: the longer you stay up, the more calories you need to fuel those waking hours. And some researchers have also found that a lack of sleep negatively affects insulin sensitivity, which in turn increases levels of appetite-stimulating hormones.
Now a new study on sleep deprivation and cravings, published in the journal Sleep, hints at yet another reason for those fatigue-linked food cravings: The sleepier you are, the higher your levels of endocannabinoids, the natural compounds your body produces to help regulate appetite by enhancing the “hedonic,” or pleasurable, aspects of eating in your brain.
Endocannabinoids are so-named because they bind to receptors in the brain that can also respond to the active ingredient in cannabis -- you know, weed. They also help regulate stress, immune response and pain.
While the study's lead researcher Erin Hanlon wouldn’t go so far as to say being sleep-deprived is like being high, as some other news organizations have suggested, she did say that sleep deprivation does appear to activate the endocannabinoid system and produce the same increased appetite.
In other words, getting too little sleep will give you the munchies.
"Sleep restriction seems to activate the endocannabinoid system, as does marijuana," Hanlon explained. "That is perhaps how [sleepy people] are getting these increases in eating and appetite."
In the small study, 14 healthy, normal-weight adults aged 18 to 30 were randomized to either one of two states. The first group, in the “normal sleep” setting, got to spend 8.5 hours a night in bed from 11 p.m. to 7:30 a.m., four days in a row. The second group endured a restricted sleep schedule from 1 a.m. to 5:30 a.m. for four days. For both, no naps were allowed, and participants were confined to a private room where they did sedentary activities while awake. Four weeks later, participants switched and experienced the other sleep schedule.
After each of the four-day sleep experiments were over, the participants fasted in the mornings but were invited to indulge in three food settings: A late lunch buffet, an afternoon snack bar and a dinner buffet. The late lunch buffet was tailored specifically to their dietary preferences, including things like pizza, burgers, baked chicken and pasta. A snack bar in their private rooms contained foods like cookies, chocolate, gummy candy, chips, salsa and guacamole. The dinner buffet looked the same as the first.
Researchers found that both groups of participants ate the same number of calories during their buffet lunch -- about 90 percent of their caloric needs -- whether or not they had just emerged from a normal sleep or a restricted sleep environment. That makes sense; after all, they were hungry and hadn’t eaten since the night before.
But the participants who had just completed a restricted sleep schedule couldn’t stop eating, despite the fact that they had just consumed most of their daily calories in one sitting at the buffet lunch. After the meal, they snacked harder, and on foods with nearly twice as much fat and protein, than the people who had just emerged from the normal sleep experiment.
Finally for dinner, both sleep groups ate about the same number of calories and carbs, fat and protein. This was also surprising, given that the restricted sleep group had snacked consistently between lunch and dinner, but the extra food doesn’t seem to have had an effect on their hearty appetites for dinner.
Researchers suspect that varying levels of endocannabinoids in the body can explain the difference in the way these two groups approached the buffet tables and snack bars. For instance, they found that when participants were in the “normal sleep” condition, endocannabinoid levels peaked in the early afternoon, around lunch time. But when participants were in the “restricted sleep” condition, levels of endocannabinoids rose an average of 33 percent as a whole. The peak also arrived later and lasted longer, from 2 p.m. to 9 p.m.
The rising level of endocannabinoids, as well as their late peak and extended peak hours, may be the reason why participants who had emerged from the restricted sleep schedule ate so much more food than they did after emerging from the normal sleep schedule. Researchers concluded that altering the normal rhythm of endocannabinoids might contribute to the hunger and extra food we eat after a bad night’s sleep.
Hanlon, who is also a researcher at the University of Chicago’s Sleep, Metabolism and Health Center, says her study is another demonstration of how important regular sleep is to maintaining overall health.
“It’s important for us to get into a good routine with our sleep habits and to protect our sleep more, and not just think about it as a byproduct of the day,” said Hanlon.
Hanlon says more studies are needed to explore the link between endocannabinoid levels and hunger, but says that for people who are trying to maintain good health, getting a good night’s sleep is one of the most important things to do.