The last time I ate a Cinnabon, it was while I was sitting on the edge of a hard plastic airport seat, waiting to board an ungodly 6 AM flight. I was barely awake enough to hand my boarding pass to the TSA agent, but the smell of fresh-baked (or recently defrosted) cinnamon rolls was enough to convince my eyelids to open slightly. Come to think of it, the past three or four Cinnabons I've eaten have been jetlagged airport terminal impulse buys—but according to some scientists, that's not surprising at all.
Researchers from Northwestern University's Feinberg School of Medicine recently presented a paper suggesting that being sleep-deprived makes your brain more sensitive to food smells. To prove their hypothesis, the scientists studied the brain activity of participants after two very different nights of sleep.
According to Science News, the participants were partially sleep-deprived, periodically interrupted during the night and limited to four total hours of shut-eye. The next day, they were asked to rate the "pleasantness and intensity" of both sweet and savory high-calorie food smells, like potato chips and—yes!—cinnamon rolls. They were also asked to rate a number of non-food smells, like the scent of decidedly inedible fir trees. While the participants sniffed, the researchers used functional magnetic resonance imaging (fMRI) to measure the activity in certain areas of their brains. Several weeks later, the smell test was repeated, but the participants were allowed to sleep a full eight hours the night before.
"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," study co-author Surabhi Bhutani told Science News. "That spike wasn't seen in response to nonfood odors."
What does that mean? For starters, it means I can't be held responsible for those early morning Cinnabinges. To the researchers, though, it could help further understand the correlation between sleep deprivation and weight gain. "The neural mechanisms in underlying sleep-dependent increases in appetite and food intake are currently unclear," the authors wrote.
They're just the most recent group of lab rats who have tried to untangle the connections between being tired and being overweight. In 2013, a group of psychologists from the University of California, Berkeley examined the relationship between sleep deprivation and cravings for high-calorie foods and discovered, perhaps unsurprisingly, that yes, people who are sleep-deprived want to stuff their faces with terribly unhealthy things. PubMed has a stack of similar studies with provocative titles like "Acute sleep deprivation enhances the brain's response to hedonic food stimuli" and "Acute sleep deprivation increases portion size and affects food choice in young men."
I'm no scientist, but all of that probably means I should either book a later flight or pick the airline that doesn't board right beside a Cinnabon. Either way, this is your fault, Brain.