The Role of Altered Nutrient Partitioning in Food Reward

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.


Eligibility Criteria:
Inclusion Criteria:

1. BMI between 18.5-40 kg/m2
2. Not pregnant or planning to become pregnant during study participation
3. Residing in the Roanoke area and/or willing/able to attend sessions at the Fralin Biomedical Research Institute
4. Able to speak and write in English
5. Specific to fMRI scan only: BMI between 25-35 kg/m2

Exclusion Criteria:

1. Current inhaled nicotine use
2. History of alcohol dependence.
3. Current or past diagnosis of diabetes or thyroid problems.
4. Glycated hemoglobin (Hemoglobin A1C) \>5.7%
5. Taking medications known to influence study measures (including antiglycemic agents, thyroid medications, sleep medications)
6. Active medical or neurologic disorder.
7. Recent change in body weight (gain or loss of \> 5 lbs within the past 3 months)
8. Current shift work (typical pattern of work/activity overnight)
9. Previous weight loss surgery
10. Adherence to a special diet within the past 3 months (e.g., low-carb or ketogenic diet, exclusion of food groups/specific macronutrients, intermittent fasting, etc.)
11. Allergy to any food or ingredient included in the study diets, meals, or beverages
12. Currently pregnant or planning to become pregnant during study participation
13. Claustrophobia
14. Contraindications for MRI, including pacemaker, aneurysm clips, neurostimulators, cochlear or other implants, metal in eyes, regular work with steel, etc. (Note: This is an fMRI-specific exclusion criterion. Participants may be allowed to participate in all other study sessions and measures that do not involve fMRI.)
15. Contraindications for bioelectrical impedance analysis, specifically implanted devices