If you are like most people, you do not need a scientific study to tell you that you probably eat more — and worse — when you’re tired. You have plenty of experience to do that for you: the late-night leftover binges when you’re crashing on a work deadline, the massive carb-y breakfasts the morning after a bout of insomnia.
But while you may already be aware that this is very much a thing, research can be useful explaining why it happens. One 2013 study, for instance, found that a lack of sleep weakens people’s ability to resist cravings for high-calorie foods; another study, published last year, discovered that sleep-deprived brains contained higher levels of a naturally occurring chemical called 2-arachidonoylglycerol, or 2-AG — a chemical similar to the ones in cannabis that give you the munchies.
And in research presented last week at the annual meeting of the Cognitive Neuroscience Society, a team of scientists offered up another explanation: Being tired, it seems, kicks your sense of smell into high gear — but only when what you’re smelling is food-related. Science News explained:
Adults operating on only four hours of sleep inhaled food odors such as those from potato chips and cinnamon rolls, and nonfood smells like fir trees while undergoing functional MRI scans. (The scientists carefully controlled participants’ food intake throughout the day.) A few weeks later, the same participants repeated the experiment — this time with a full eight hours of sleep.
When tired, participants showed greater brain activity in two areas involved in olfaction — the piriform cortex and the orbitofrontal cortex — in response to food smells than they did when well rested. That spike wasn’t seen in response to nonfood odors, says study coauthor Surabhi Bhutani, of the Northwestern University Feinberg School of Medicine in Chicago.
And that heightened sense of smell, it seems, might make it harder to turn down whatever it is you’re smelling. Odor is one of the main ways we experience our food, and if your sleepy-but-superpowered nose happens to catch a whiff of greasy cheese as you pass by your neighborhood pizza place, it’s going to seem that much more tempting. One easy and even enjoyable trick for eating healthier, it seems, may be this: Try to get a good night’s rest.