Biobehavioral Reward Responses Associated With Consumption of Nutritionally Diverse Ultra-Processed Foods

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.

Eligibility Criteria:
Inclusion Criteria:

* 18 to 65 years old
* BMI ≥ 30 kg/m2
* Endorse liking the test snack foods at a 6 on a 1-10 scale
* Live in the greater Philadelphia area and are willing/able to participate in six in-person assessments
* Can access and are willing/able to use a smartphone
* Able to give consent

Exclusion Criteria:

* Unable to fluently speak, write, and read English
* BMI below 30 kg/m2
* Self-report dietary allergies or aversions to the test snack foods
* Current diagnosis of type 1 or 2 diabetes (HbA1c \> 6.5; will be confirmed by blood test at baseline) or self-reported diagnosis of hypertension
* Self-report a cardiovascular event (e.g., stroke, myocardial infarction) in the last 12 months
* Self-report current use of medications that may influence the metabolic responses of interest or inhibit appetite (e.g., metformin, liraglutide)
* Self-report a loss of ≥ 5% of their body weight in the last 6 months, as this may influence their food choices
* Self-report severe symptoms of mood (Beck Depression Inventory score ≥ 29), anxiety, and any severity of thought disorders
* Self-report severe binge eating disorder or full criteria bulimia nervosa
* Self-report active substance-use disorders
* Self-report current, active suicidal ideation, and/or a suicide attempt in the past year (will be referred to psychiatric treatment facilities in the greater Philadelphia area)
* Self-report a history of bariatric surgery
* Self-report current involvement in weight loss treatment or self-directed weight loss attempt
* Women who are nursing, pregnant, or planning to become pregnant in the next 3 months
* Does not have access or are not willing to use a smartphone