The Role of Altered Nutrient Partitioning in Food Reward

Study Summary

Obesity remains a public health epidemic despite substantial advances in treatment strategies and therapies in the last decade. Effective strategies to support maintenance of improved metabolic health and reduced body weight are still needed. Signals from the gut to the brain are important in regulating metabolism and energy balance and have been linked with food reward and preference in metabolically healthy individuals with normal body mass index. In particular, post-ingestive signaling related to glucose metabolism has been linked with food reward and preference. However, not much is known about how these gut and brain signals interact to influence eating behaviors in states of obesity or altered metabolic health. In addition, evidence in rodent models and human studies indicates obesity is associated with a blunted brain response to foods compared with normal body weight. However, whether altered nutrient utilization, termed metabolic inflexibility, influences the relationship between obesity and food reward has yet to be studied. The overall objective of this proof-of-concept pilot study is to assess the feasibility of measuring reward response following a flavor-nutrient conditioning paradigm across the normal to obese body mass index (BMI) range and in states of altered metabolic health. The aims of this study are: 1) to determine whether differences in reinforcement learning/flavor-nutrient conditioning of carbohydrate can be measured across the body mass index range; and 2) to determine the feasibility of assessing metabolic flexibility and whether a relationship between metabolic flexibility and calorie-predictive reward can be detected.

Primary Outcome

Subjective ratings of liking of flavors used in the intervention were assessed at baseline and after the intervention. The generalized Labeled Magnitude Scale will be used. The scale is anchored by descriptors of "Most Disliked Sensation Imaginable" and "Most Liked Sensation Imaginable" at the lower and upper ends, respectively. The score is determined by the place on the scale participants select (range of scale is 0-100). An increase in score from baseline to post-intervention indicates an inc

Interventions

• OTHER Conditioned Stimulus + (CS+): Flavored beverage solution with 75 calories of sucrose
• OTHER Conditioned Stimulus - (CS-): Flavored beverage solution with sweetness-matched sucralose
• OTHER High-Fat Test Meal Inside a Metabolic Chamber
• OTHER High-Carbohydrate Test Meal Inside a Metabolic Chamber
• OTHER fMRI Scan