A poor night’s sleep can leave us feeling cranky or drowsy during the day, but it can also increase the likelihood that we crave junk food the next day, according to researchers from Northwestern University.
“When you’re sleep deprived, [certain] brain areas may not be getting enough information, and you’re overcompensating by choosing food with a richer energy signal,” said researcher Thorsten Kahnt. “But it also may be that other areas fail to keep tabs on the sharpened signals in the olfactory cortex. That could also lead to choosing doughnuts and potato chips.”
What causes the cravings?
The researchers had nearly 30 adults participate in a two-part study. The first part involved directly monitoring participants’ sleeping and eating habits; the second part took a more biological approach to determine how the olfactory system and other factors could be responsible for changes in appetite.
For the sleeping portion, the researchers had half the participants sleep through the night normally. However, the other half of the participants got just four hours of sleep at night. This went on for four weeks before the groups switched sleeping schedules.
Following each night of sleep, all of the participants ate the same meals throughout the day, but they had the freedom to choose from a wide variety of snacks that were available to them in between meals.
After looking at participants’ fMRI scans, the researchers learned that lack of sleep not only sharpened their ability to differentiate between food and non-food-related scents, but it also increased cravings for foods higher in both calories and fat.
Avoid junk food on short amounts of sleep
In addition to the biological changes, the researchers also observed that the participants changed their snacking habits based on when they slept longer versus when they only got four hours of sleep.
“After being sleep deprived, they ate food with higher energy density (more calories per gram) like doughnuts, chocolate chip cookies, and potato chips,” said Kahnt.
Knowing how sensitive the nose can be to food smells following a bad night of sleep, particularly unhealthy foods, the researchers had some practical advice for consumers who may be tempted to indulge their cravings.
“Our findings suggest that sleep deprivation makes our brain more susceptible to enticing food smells, so maybe it might be worth taking a detour to avoid your local doughnut shop next time you catch a 6 a.m. flight,” said Kahnt.