People tend to snack at night because some areas of the brain do not get the same 'high' from food in the evening, a new study has found.
Researchers from Brigham Young University used MRI to measure how people's brains respond to high- and low-calorie food images at different times of the day.
The results showed that images of food, especially high-calorie food, can generate spikes in brain activity, but those neural responses are lower in the evening.
"You might over-consume at night because food is not as rewarding, at least visually at that time of day," said lead author Travis Masterson.
"It may not be as satisfying to eat at night so you eat more to try to get satisfied," Masterson said.
The study, which appears in the journal Brain Imaging and Behavior, also found that participants were subjectively more preoccupied with food at night even though their hunger and 'fullness' levels were similar to other times of the day.
For the study, researchers teamed up with BYU neuroscientist Brock Kirwan to use functional MRI to monitor the brain activity of study subjects while they viewed images of food.
The participants viewed 360 images during two separate sessions held one week apart - one during morning hours and one during evening hours.
Subjects looked at images of both low-calorie foods (vegetables, fruits, fish, grains) and high-calorie foods (candy, baked goods, ice cream, fast food).
As expected, the researchers found greater neural responses to images of high-calorie foods. However, they were surprised to see lower reward-related brain reactivity to the food images in the evening.
"We thought the responses would be greater at night because we tend to over-consume later in the day," said study co-author Lance Davidson, a professor of exercise sciences.
"But just to know that the brain responds differently at different times of day could have implications for eating," he said.
