If you have trouble resisting the siren call of the refrigerator late at night, it may be your brain's fault.

Researchers at Brigham Young University found that the reason you snack at night is because your brain doesn't get the same "food high" in the evening as it does at other times of the day.

Researchers at BYU collaborated with neuroscientist Brock Kirwan to use functional MRI to monitor the brain activity of people while they looked at pictures of food. Their intent was to better understand if the time of day influences the brain's response to pictures of food.

Subjects viewed 360 images during two sessions conducted one week apart. One session took place during the morning and the other during evening hours.

Participants looked at images of both high-calorie foods (candy, baked goods, ice cream) and low-calorie foods (vegetables, fruits, fish, grains). The brains of both men and women spiked when shown images of high-calorie foods, but the researchers found that the reward areas of the brain showed less activation in the evening.

"We thought the responses would be greater at night because we tend to over-consume later in the day," said study coauthor 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."

"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."

Even though their brains showed a difference in activity at night, participants also reported that their hunger and "fullness" levels in the evening were similar to other times of the day.

Have the results of his research changed Masterson's late-night eating habits? "I tell myself, this isn't probably as satisfying as it should be," he said. "It helps me avoid snacking too much at night."