Food smells better to sleepyheads

SAN FRANCISCO, Calif. — Foods may smell more appetizing when you’re tired.

Getting too little sleep seems to increase the brain’s sensitivity to food smells, a new study finds. This suggests sleep-deprived people might finds snacks more enticing. If true, this could help explain why people who burn the candle at both ends tend to eat more — and often weigh more.

Surabhi Bhutani is a nutrition scientist at Northwestern University’s Feinberg School of Medicine in Chicago. She shared her team’s new findings here on March 27 at the Cognitive Neuroscience Society’s annual meeting.

The group brought adults into their lab who had had slept only four hours the night before. Each inhaled a sequence of food odors. They might, for instance, include the scent of potato chips or cinnamon rolls. Each was asked to sniff nonfood smells as well, such as the scent of fir trees. All of this sniffing took place as their brains were being recorded with a functional MRI scanning device. These machines highlight regions where blood flow is high. Such areas point to which parts of the brain are most active at that point in time.

A few weeks later, the same participants repeated the experiment. This time, however, each had gotten a full eight hours of sleep the night before. And now the areas of high brain activity were somewhat different.

When tired, participants showed greater brain activity in two areas involved in the sense of smell. One is the piriform (PEER-ih-form) cortex, the other the orbitofrontal (OR-bih-tow-FRON-tul) cortex. But this heightened response to food smells did not show up after a good night’s sleep. Such a heightened response also did not appear when people had viewed pictures of things other than food.

The findings are preliminary. That means they need to be confirmed with a bigger follow-up study. Bhutani notes that her team’s data do fit, however, with previous research which showed a link between too little sleep, excess calorie consumption and weight gain.