Neural and Metabolic Factors in Carbohydrate Reward

Dietary factors contributed to nearly 50% of all cardiometabolic deaths in the US in 2012, making it one of the leading causes of preventable death in the US, second only to tobacco use. Human diets and food choices can't help but be influenced by the ubiquitous availability of processed foods of high-energy density and low nutrient content, consumption of which can lead to obesity, type II diabetes, heart disease, and other types of metabolic dysfunction. Surprisingly, food reinforcement does not rely on perceived energy density. Rather food reinforcement is associated with actual energy density and therefore, on an implicit knowledge of caloric content. That implicit knowledge must have a neural signature and a mechanism by which the gut communicates nutritive value to the brain. There is evidence, at least for fat and carbohydrates, that these pathways are separable, but terminate in a common neural structure, the dorsal striatum or caudate. This could be one mechanism by which modern processed foods high in both fat and carbohydrate are so sought after and readily consumed, In fact, when experimentally tested, fat and carbohydrate combinations were more reinforcing calorie for calorie than fat or carbohydrates alone and the level of reinforcement correlated with activity in reward- related brain areas. Beyond simple reinforcing value, it is known from the literature on drugs of abuse that the faster a drug is arrives at the brain, the higher it's abuse potential, however, little is known about how the kinetics of nutrient excursion influence food preference, choice, and brain activity. This project aims to test this specifically for carbohydrate reward.

Inclusion Criteria: 1. BMI between 18.5-30 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 Exclusion Criteria: 1. Current inhaled nicotine use 2. History of alcohol dependence. 3. Current or past diagnosis of diabetes or thyroid problems. 4. Taking medications known to influence study measures (including antiglycemic agents, thyroid medications, sleep medications) 5. Active medical or neurologic disorder. 6. Current shift work (typical pattern of work/activity overnight) 7. Previous weight loss surgery 8. 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.) 9. Allergy to any food or ingredient included in the study diets, meals, or beverages 10. Currently pregnant or planning to become pregnant during study participation 11. Claustrophobia 12. Contraindications for MRI, including pacemaker, aneurysm clips, neurostimulators, cochlear or other implants, metal in eyes, regular work with steel, etc.