New research documents how brains respond to food images at night.
After gobbling the fourth Oreo in a row while bathed in refrigerator light, have you ever thought, “That wasn’t enough,” and then proceeded to search for something more?
Researchers at BYU have shed new light on why you, your friends, neighbors and most everyone you know tend to snack at night: some areas of the brain don’t get the same “food high” in the evening.
In a newly published study, exercise sciences professors and a neuroscientist at BYU 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.”
The study, which appears in academic journal Brain Imaging and Behavior, also reports 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.
Masterson, who carried out the research for his master’s thesis under faculty advisor James LeCheminant, said the intent was to better understand if time of day influences neural responses to pictures of food.
The 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 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.”
Nevertheless, researchers noted that the study is preliminary and additional work is needed to verify and better understand the findings. The next research steps would be to determine the extent that these neural responses translate into eating behavior and the implications for weight management.
Masterson, who is heading to Penn State University to work on his PhD in the fall, said the study has helped him pay better attention to how food makes him feel both in the morning and the evening. And as for his 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.”
Source: Todd Hollingshead – Brigham Young University
Image Credit: The image is credited to Jaren Wilkey/BYU
Original Research: Abstract for “Neural reactivity to visual food stimuli is reduced in some areas of the brain during evening hours compared to morning hours: an fMRI study in women” by Travis D. Masterson, C. Brock Kirwan, Lance E. Davidson, and James D. LeCheminant in Brain Imaging and Behavior. Published online March 10 2015 doi:10.1007/s11682-015-9366-8
Neural reactivity to visual food stimuli is reduced in some areas of the brain during evening hours compared to morning hours: an fMRI study in women
The extent that neural responsiveness to visual food stimuli is influenced by time of day is not well examined. Using a crossover design, 15 healthy women were scanned using fMRI while presented with low- and high-energy pictures of food, once in the morning (6:30–8:30 am) and once in the evening (5:00–7:00 pm). Diets were identical on both days of the fMRI scans and were verified using weighed food records. Visual analog scales were used to record subjective perception of hunger and preoccupation with food prior to each fMRI scan. Six areas of the brain showed lower activation in the evening to both high- and low-energy foods, including structures in reward pathways (P < 0.05). Nine brain regions showed significantly higher activation for high-energy foods compared to low-energy foods (P < 0.05). High-energy food stimuli tended to produce greater fMRI responses than low-energy food stimuli in specific areas of the brain, regardless of time of day. However, evening scans showed a lower response to both low- and high-energy food pictures in some areas of the brain. Subjectively, participants reported no difference in hunger by time of day (F = 1.84, P = 0.19), but reported they could eat more (F = 4.83, P = 0.04) and were more preoccupied with thoughts of food (F = 5.51, P = 0.03) in the evening compared to the morning. These data underscore the role that time of day may have on neural responses to food stimuli. These results may also have clinical implications for fMRI measurement in order to prevent a time of day bias. "Neural reactivity to visual food stimuli is reduced in some areas of the brain during evening hours compared to morning hours: an fMRI study in women" by Travis D. Masterson, C. Brock Kirwan, Lance E. Davidson, and James D. LeCheminant in Brain Imaging and Behavior. Published online March 10 2015 doi:10.1007/s11682-015-9366-8