The Neuroscience of Snacking
Brain responses to snacks, as recorded by EEG, indicate how much one likes them.
The snacks people prefer most elicit the strongest responses
Eating a lot of a snack decreases brain response to the consumed snack.
Individual preferences are the driving forces behind our snack choices. While some of us prefer chocolate, others like chips or peanuts better. But what happens in your brain once you’ve eaten that whole bag of chips?
A neuroscientific study from 2019 used electroencephalography (EEG) to record brain responses to snacks. EEG measures the brain’s electrical activity with electrodes fixed to an elastic cap worn like a hat. The study showed that individual preferences for two types of chocolate (milk chocolate or white chocolate) and edible wafer paper were reflected in brain responses, with the largest response for the highly preferred snack ( Peterburs, Sannemann, & Bellebaum, 2019 ).
In a new follow-up study ( Huvermann, Bellebaum, & Peterburs, 2021 ), researchers at Heinrich-Heine-University Düsseldorf in Germany and MSH Medical School Hamburg investigated how the neural coding of snack preferences was affected by the consumption of one's most preferred snack.
Healthy adult volunteers whose preferences for sweet (e.g., chocolate or gummy bears), savory (e.g., chips, peanuts, or pretzels), and neutral snacks (e.g., rice wafers or crispbread) had been assessed participated in two test sessions. In each session, they performed an experimental task on the computer while brain responses were recorded with EEG. In the task, participants opened virtual doors to reveal sweet, savory, or neutral snacks. They were informed that they would receive the snack they found most often at the end of the session. Crucially, participants fasted for 6 hours before each session. In one session, they were given the opportunity to eat as much as they wanted of their most preferred snack prior to task performance while EEG was prepared. In addition, participants watched a TV show to encourage snacking behavior. In the other session, they did not receive any snacks but the procedure was otherwise identical.
Results from the session without prior snacking confirmed the pattern observed in the previous study: Brain responses coded subjective preferences in a gradual manner, with the largest response for the highly preferred snack. Critically, results from the snacking session showed that prior consumption led to a diminished brain response to the highly preferred snack only. This effect mirrored a decrease in subjective desire-to-eat ratings that were also obtained for the three snacks used in the task.
This study’s results show that reward processing in the brain is not only affected by individual factors, such as subjective preferences, but also by one's current motivational state. Measuring the brain’s responses to snacks depending on prior consumption may be a promising approach to further characterize altered neural processing of food rewards in eating disorders, such as binge eating disorder or anorexia nervosa, and obesity.
So what do these findings mean for you? If you find that you do not like your favorite snack anymore after eating lots of it, blame your brain.