Late-night snack urges that drive us to the darkened kitchen — soon illuminated by the refrigerator light — may be all in our heads, not our stomachs, a study suggests.
It's all down to the fact that our brains' responses to the prospect of food are dissimilar at different hours of the day, researchers at Brigham Young University have found.
At night, they've found, our brains have a diminished reward-related response to the look of food, so we try to compensate by eating more of it, they report in the journal Brain Imaging and Behavior.
"You might over-consume at night because food is not as rewarding, at least visually at that time of day," says study leader Travis Masterson. "It may not be as satisfying to eat at night so you eat more to try to get satisfied."
Participants in the study were also more preoccupied with food late at night, subjectively, despite the fact that their levels of hunger or "fullness" were about the same as at other periods in the day, he says.
The participants' brain activity was recorded using functional MRI scans as they were shown images of various kinds of foods; they viewed 360 images in two separate sessions.
The sessions were one week apart, with a crucial difference — one session was during the morning hours, while the other was held during the evening hours.
The subjects were shown images with both low-calorie and high-calorie foods, and showed greater brain responses to the high-calorie baked goods, ice cream, candy and fast food — as was expected.
What was not expected was the reduced reward-related brain responses to the food images viewed during the evening, the researchers say.
"We thought the responses would be greater at night because we tend to over-consume later in the day," says study co-author Lance Davidson, a BYU professor of exercise sciences. "But just to know that the brain responds differently at different times of day could have implications for eating."
The finding that the time of day can have an impact on the brain's response to food stimuli could have implications for our understanding of people's eating behaviors and might offer help in weight management, the researchers say.
Masterson admits the study findings have helped him reduce his own late-night trips to the pantry.
"I tell myself, this isn't probably as satisfying as it should be," he says. "It helps me avoid snacking too much at night."
