Gut-brain interactions in food reward

Food choice and preference have been linked to post-ingestive consequences of food consumption. Many ultra-processed foods deliver calories rapidly and are highly rewarding. In literature surrounding substances of abuse, the speed at which a drug reaches the brain affects its abuse potential; this is known as the "rate hypothesis." Here, we test whether the rate hypothesis of addiction may apply to food, specifically whether caloric availability, or the speed at which carbohydrate becomes available for use, contributes to food reward and preference. To do this, we use beverages with novel flavors (conditioned stimulus (CS)) mixed with either a slow metabolizing carbohydrate (maltodextrin and inulin; CS+Slow), a fast-metabolizing carbohydrate (sucrose; CS+Fast), or no carbohydrate (sucralose; CS-). Participants are given each of these drinks 6 times to consume (conditioning period). 2 of these consumption periods occur during in-lab sessions. In one session, blood glucose is measured over one hour post-consumption. In another, we perform indirect calorimetry to assess post-consumption changes in substrate oxidation rates. At the post-testing session, changes in self-reported liking, wanting, and ad libitum intake of each beverage are recorded. Brain response to each flavor cue (without calories) is measured using fMRI at the post-test. We hypothesize the flavor paired with the CS+Fast will be the most liked, wanted, and consumed. We expect greater BOLD (blood oxygenated level dependent) activation to the CS+Fast relative to the CS+Slow and CS- in the nucleus accumbens and hypothalamus. This is an ongoing study and, here, we present our preliminary analysis of the data.