Overview
This study experimentally investigates whether a reduction in ultra-processed (UP) food intake (1) causes aversive withdrawal symptoms in humans, (2) increases the motivational salience of UP food cues and, if so, (3) whether these factors undermine the ability to adhere to a low-UP diet. The following aims and hypotheses are tested:
Aim 1: To investigate whether aversive physical, cognitive, and affective withdrawal symptoms emerge in response to reduced UP food intake compared to a high-UP diet, and whether this predicts failure to adhere to a low-UP diet.
H1a: Reducing UP food intake will result in aversive physical, cognitive, and affective withdrawal symptoms, as indicated by 1) ecological momentary assessment (EMA) reports of aversive withdrawal symptoms, and 2) heart rate reactivity and subjective distress to an in-lab stressor.
H1b: Aversive symptoms of UP food withdrawal will predict greater UP food intake and higher blood glucose levels when trying to adhere to a low UP diet.
Aim 2: To investigate whether increased motivational salience of UP food cues emerges in response to reduced UP food intake, and whether this predicts failure to maintain a low-UP diet.
H2a: Reducing UP food intake will result in increased motivational salience of UP food cues, as indicated by 1) EMA reports of UP food craving, 2) heart rate reactivity and subjective craving in a simulated fast-food restaurant, 3) heightened reinforcement value for UP food relative to other reinforcers, and 4) greater reward-related neural response to UP food cues.
H2b: Increased motivational salience of UP food cues will predict greater UP food intake and higher blood glucose levels when trying to adhere to a low UP diet.
Description
The study will include a combination of in-person, at-home, and virtual activities over the course of ~14 days (contingent on scheduling, this duration may vary and particularly between in-person visits #1 and #2). Participants complete three in-lab visits. Visit 1 and 2 will each followed by a week of remote data tasks (e.g., EMA, continuous glucose monitoring, physical activity and sleep tracking (Fitbit), and two 24-hour dietary recall interviews).
During in-lab visit #1, participants will complete questionnaires, behavioral tasks, and interviews, and will have body composition measurements taken (height, weight, Inbody scan). Participants will complete the remote tasks for the following week while eating their typical diet (i.e., baseline period).
During in-lab visit #2, participants will complete questionnaires, interviews, and body composition measurements (height, weight, Inbody scan). Participants are randomly assigned to one of three conditions--control (i.e., high UP), self-guided low UP, or meals provided low UP--and will follow instructions about how to eat consistent with their condition during week 2 of remote data collection (i.e., dietary intervention period).
During in-lab visit #3, participants will complete questionnaires, behavioral tasks, body composition measurements (height, weight, InBody scan), and an fMRI scan.
Participants are contacted 1- and 3-months later to complete a short follow-up survey and provide information about their current diet.
Eligibility
Inclusion Criteria:
- 25 to 60 years of age
- English-speaking
- Must own an Android or iPhone Smartphone
- Live within a 1-hour radius of the laboratory
- endorsement of > 4 symptoms on the YFAS 2.0 completed during eligibility screener; at the time of consent, symptom count must remain above threshold for food addiction (this discrepany is based on a previously found tendency during pilot testing to overestimate food addiction symptoms at the time of screening)
- endorse daily intake of multiple UP foods
- likes chocolate milkshake (fMRI)
- willing to follow dietary instructions provided by team
- willing to come to lab 3 times
Exclusion Criteria:
- participants with a self-reported BMI < 18.5 and > 40
- current diagnoses of disorders that can impact reward, metabolic functioning, or the ability to complete the imaging protocol (e.g., seizures, Tourette's, cancer, Irritable bowel syndrome, Inflammatory bowel disease, Hypothyroidism, substance use disorder, ADHD)
- Type 1 or Type 2 diabetes, pre-diabetes, hypoclycemia
- history of food allergies or restrictive dietary requirements (e.g., vegan)
- medications that impact appetite or reward functioning (e.g., anti-psychotic medication, insulin)
- history of diagnosis of a severe mental illness (e.g., bipolar, schizophrenia, psychotic disorder)
- a diagnosis of a restrictive eating disorder (anorexia nervosa, bulimia nervosa, purging disorder) within the last 5 years
- more than a 20-pound weight fluctuation in the last three months
- prior weight loss surgery (e.g., bariatric surgery)
- current pregnancy, breast-feeding, trying to get pregnant, or within six months of having given birth
- high levels of caffeine (i.e., average daily intake over 600mg) intake
- use of tobacco, nicotine, cannabis products within the past month and/or unwillingness to abstain from these substances during the main portion of the study
- high-risk alcohol use (based on the AUDIT)
- high levels of picky eating
- fMRI contraindications (e.g., claustrophobia, metal implants)
- red/green color blindness
- frequent (i.e., weekly) night shift work or irregular shifts and for abnormal sleep patterns (i.e., wake up time after 11am)
- inability to complete a random report within 90 minutes
- THC Cannabis within the past week