The changing food environment, with increasingly abundant ultra-processed food (UPF) options, may directly contribute to rising rates of obesity, though it is unknown which ingredients in UPF elevate their reinforcing nature in a way that may lead to overconsumption. The proposed study is the first to systematically examine differences in the rewarding characteristics of and physiological and metabolic responses to UPFs that are high in fat, refined carbohydrates (like sugar), or both. Understanding the biobehavioral underpinnings that enhance the reinforcing potential of ingredients in UPF (e.g., fat vs. refined carbohydrates) can inform novel intervention targets for the treatment of overeating and obesity.

The abundance of ultra-processed foods (UPFs) in our environment has led to excessive calorie intake and been cited as perpetuating the obesity epidemic. UPFs do not exist in nature and are created to maximize palatability through the additions of fat, refined carbohydrates (RC), and/or sodium (e.g., chocolate, potato chips). Emerging research suggests UPFs may be reinforcing akin to rewarding substances like alcohol. However, empirical investigation of which ingredients in UPFs directly motivate overeating is in its nascent stages. This study will be the first to combine biological and behavioral methods used in addiction research with assessments of food reward, to delineate the mechanisms by which fat and RC drive UPF reinforcement and influence future consumption.

Individuals (n=50) with obesity will be recruited for the current study. Participants will attend four appointments (order randomized/counterbalanced) and will consume a snack consisting of 1) UPF high in fat + RC (UPF+FRC), 2) UPF high in fat (UPF+F), 3) UPF high in RC (UPF+RC), or 4) minimally processed foods (MPF). At each assessment, subjective experiences and metabolic responses will be assessed before and up to 120 minutes after consumption of each snack. An ad-libitum eating period for each food condition will follow to evaluate associations of metabolic/behavioral responses with subsequent intake. For five days after each appointment, participants will use ecological momentary assessment (EMA) to assess subjective experiences and real-world reported consumption of UPF+FRC, UPF+F, UPF+RC, and MPF.

Inclusion Criteria Men and women Age 18-65 years BMI ≥ 30 kg/m2 Endorse liking the foods included in the compulsory test snacks at a 6 on a scale from 1-10 No history of severe psychiatric illness; current mild to moderate severity of depression, anxiety, or binge eating disorder, determined by the behavioral evaluation and the screening measures will be included Live in the greater Springfield, Oregon area and are willing/able to participate in six in-person assessments Can access and are willing/able to use a smartphone

Exclusion Criteria Medical condition that may limit consumption of compulsory test snack foods or impact metabolic responses to food consumption Type I or II diabetes (HbA1c > 6.5 based on blood test) Uncontrolled hypertension (blood pressure ≥ 140/90 mm Hg) Cardiovascular event (e.g., stroke, myocardial infarction) in the last 12 months Individuals with dietary allergies of aversions to the test snack foods Individuals taking medications that may influence the metabolic responses of interest (e.g., metformin) Individuals who are actively pursuing weight loss or have lost ≥ 5% of their initial weight in the last 6 months Severe symptoms of mood, anxiety, and any severity of thought disorders Severe binge eating disorder or full criteria bulimia Persons with active substance-use disorders Current, active suicidal ideation, and/or a suicide attempt within the past year History of bariatric surgery Women who are nursing, pregnant, or planning to become pregnant in the next three months Self-report current diagnosis of a transferrable blood condition (including HIV, hepatitis B, hepatitis C, or syphilis) Self-report prior history of being dizzy or anxious during blood draws and/or technician not being able to find a vein.

The project will generate multi-modal data from 50 adults with obesity, including repeated measures of subjective reward responses, physiological and metabolic markers (e.g., heart rate, insulin, glucose, ghrelin, leptin), ecological momentary assessment (EMA) reports, and behavioral task performance (e.g., Stroop, delay discounting, relative reinforcing value). Data will include numeric, categorical, and time-series variables collected across six study visits and four EMA sampling periods. All data will be de-identified and stored in structured formats suitable for statistical analysis.

Data associated with a study publication will be made available upon first publication of the findings. Data will be available indefinitely.

Dr. LaFata (PI) will be responsible for overseeing the data management and sharing of this project. Dr. LaFata will administer data collection, storage, and repository training to the research coordinator and to any volunteer study staff, who must demonstrate competence in all tasks before commencing their responsibilities. All project staff who use data will have received training in responsible data practices.

ORI- Community and Evaluation Services will be conducting routine monitoring inspection of randomly selected studies that have indicated a Data and Sharing Management Plan and have received or been awarded funds through NIH and subject to the NIH Data Sharing Policy.