The aim of this project is to test the feasibility, acceptability and clinical impact of a mobile app-based intervention (FoodTraining) to strengthen food-related inhibitory control over 4 weeks, in a sample of people with eating or weight disorders (i.e. obesity, binge-eating disorder (BED), or bulimia nervosa (BN)) receiving standard outpatient treatment (i.e., treatment as usual (TAU) encompassing guided self-help or psychotherapy, pharmacological therapy or diet). The training will be offered in addition to TAU (experimental group) and compared to TAU alone (control group).

Participants will complete questionnaires to measure eating behaviour, eating disorder psychopathology, symptoms of anxiety, depression and stress, social functioning and quality of life at baseline, 4 and 8 weeks. They will also complete momentary assessments using a mobile application (FoodTracker) to report on food intake along with related thoughts, emotions, and behaviours and will wear small, non-invasive sensors to track real-time fluctuations in glucose levels for 15 days.

Participants will also perform a food-related go-no go task and a food-related temporal discounting task at baseline, 4 and 8 weeks.

Finally, this study will pilot the use of a semi-structured interview to characterise the history of weight, the appetite system, eating-related habits in the family and learning of eating behaviours and attitudes in people with eating or weight disorders.

The study aims:

• To establish the feasibility, acceptability and clinical impact of a food-specific inhibitory control training delivered through a mobile App (i.e., FoodTraining) over 4 weeks in a sample of patients with obesity, bulimia nervosa or binge-eating disorder (N = 113) offered in addition to TAU, compared to TAU alone;
• To test the acceptability and adherence to the ecological momentary assessments collected through the Food Tracker App and the sensors for glucose monitoring;
• To characterise history of weight, appetite system, eating-related habits in the family and learning of eating behaviours and attitudes in people with obesity presenting for weight loss treatment.

An a-priori power analysis performed on the G*Power software, indicated that 93 participants would be needed to detect a significant 2 (group) x 3 (time) within-between interaction effect on the primary outcome measure (emotional eating and uncontrolled eating) with a small to medium effect size (Cohen's f = 0.15), a statistical power of 1-β = .80, and at a significant level α = .05, assuming a correlation among repeated measures of r = .5. To account for possible drop-out, the number will be exceeded by 20%. The final sample size that will be recruited is 113 participants.

Patients will be recruited and assessed at baseline, 4 and 8 weeks follow-up from the University Hospital in Padova (i.e., Eating Disorders Unit and Obesity Management Unit).

Assessment phase

After providing written informed consent, participants will complete a questionnaire to collect demographic information, such as gender and age. Their weight and height will be measured by a clinician. Clinical information, such as diagnosis, psychiatric/medical comorbidities and ongoing treatment will be retrieved from hospital clinical records. Participants will complete the following self-report questionnaires, measures and computerised tasks:

• The Three Factors Eating Questionnaire (TFEQ): a 51-item self-report questionnaire to assess eating-related feelings and behaviours. It comprises three subscales: cognitive restraint (i.e., efforts and worries to regulate food intake to control body weight and shape), uncontrolled eating (i.e., tendency to lose control and overeat), and emotional eating (i.e., tendency to eat in response to emotional urges, both positive and negative);
• The Dutch Eating Behavior Questionnaire (DEBQ): a 33-item self-report questionnaire grouped in 3 subscales: emotional eating (i.e., eating in response to internal emotional factors like fear, anxiety and anger), external eating (eating in response to external stimuli such as the sight and smell of food) and restrained eating (eating less than desired to lose or maintain a particular body weight);
• The Food Cravings Questionnaire-Trait (FCQ-T): a validated self-report instrument designed to assess the frequency and intensity of food cravings as a stable individual characteristic. Comprising 39 items, the FCQ-T evaluates multiple dimensions of trait food craving, including emotional triggers, cognitive preoccupation with food, lack of control, and anticipation of positive reinforcement from eating. Higher scores indicate a greater tendency to experience food cravings;
• Eating Disorder Examination Questionnaire (EDE-Q): a 28-item self-report questionnaire designed to assess the range, frequency and severity of eating disorder features. It includes the following subscales: Restraint (i.e. dietary restriction and attempts to control food intake), Eating Concern (i.e. preoccupation with food, eating, and guilt related to eating), Shape Concern (i.e. dissatisfaction, overvaluation, and preoccupation with body shape) and Weight Concern (i.e. preoccupation with weight, desire to lose weight, and fear of weight gain) and an overall Global score;
• Binge Eating Scale (BES): a self-report questionnaire to assess the severity of binge eating behavior. It includes 16 items that measure both behavioral manifestations (e.g., loss of control during eating episodes) and emotional and cognitive aspects (e.g., feelings of guilt or distress related to overeating);
• Depression Anxiety Stress Scales, Short Version (DASS-21): a 21-items screening tool to assess symptoms of depression, anxiety, and stress. It comprises three subscales: (1) Depression subscale measuring hopelessness, low self-esteem, and low positive affect; (2) Anxiety subscale assessing autonomic arousal, musculo-skeletal symptoms, situational anxiety and subjective experience of anxious arousal; and (3) Stress subscale evaluating tension, agitation, and negative affect;
• Work and Social Adjustment Scale (WSAS): a 5-item questionnaire assessing the impact of a person's mental health difficulties on their ability to function in terms of work, home management, social leisure, private leisure and personal or family relationships;
• Food-related liking and wanting, emotional states, and urge to eat visual analogue scales (0-100) will be used for subjective ratings of liking, wanting, emotional states and urge to eat following food pictures presentation;
• Yale Food Addiction Scale (YFAS): a 25-item self-report questionnaire assessing food addiction levels (compulsive consumption of palatable and hyperpalatable food items, often high in sugar, fat and salt contents, with marked activation of the reward system, and clinically significant impairment or distress on several areas of functioning);
• Barratt Impulsiveness Scale-11 (BIS-11): a 30-item self-report questionnaire to measure trait impulsivity. It encompasses three main domains: attention impulsivity (i.e. cognitive instability and inability to focus), motor impulsivity (i.e. acting without thinking), and non-planning impulsivity (i.e. lack of future orientation or forethought);
• Computerised food-related go/no-go task: it is a widely used paradigm to assess food-related response inhibition. The task will be divided into 10 blocks. In half of the blocks the pleasant stimuli (no-go stimuli) will be images of palatable foods, while in the other 5 blocks, no-go stimuli will be images of animals. In all blocks, go-stimuli will be pictures of neutral objects (e.g. office supplies, furniture). Participants will be instructed to press the spacebar on the computer keyboard as quickly as possible when they see a go stimulus (object), and to refrain from pressing any key when they see a no-go stimulus (food or animals). Each block will include 20 trials for a total of 200 trials. Numbers of errors will be used to assess inhibitory control;
• Computerised food-related temporal discounting tasks (TD task): a computerized temporal discounting task involving food and money rewards. Participants will be asked to select their preferred food by choosing one of four alternatives, which will be presented during the tasks. After selecting the preferred rewards, they will complete two tasks in a counterbalanced order. In each trial, they will have to choose between a smaller immediate reward or a larger reward delayed by one of six time intervals: 2 days, 2 weeks, 1 month, 3 months, 6 months, or 1 year. Each delay block will consist of five choices, with the delayed reward fixed at 40 units and the immediate reward adjusted based on previous choices using a titration method. The order of the delay blocks will be randomized across participants. Participants will be instructed to imagine receiving the rewards at the specified times and told there are no right or wrong answers. The trials will start with an immediate reward of 20 units; if the immediate option is chosen, its amount decreases in the following trial, and if the delayed option is chosen, the immediate amount increases. The size of adjustments halves after each choice, refining the estimate of the immediate reward equivalent to the delayed reward. The final data from each TD task will be fitted to a hyperbolic discounting function, yielding a discount rate (k) that reflects the degree to which participants prefer immediate over delayed rewards (i.e. the higher the k, the stronger the preference for immediate rewards);
• A semi-structured interview developed by the research team will be used at baseline to characterise the history of weight, the appetite system, eating-related habits in the family and learning of eating behaviours and attitudes.

A mobile App (i.e. FoodTracker), will be used to track food consumption, eating behaviours and their emotional and cognitive correlates for 3 days. Participants will be asked to complete the EMAs before and after each meal, and will also be prompted to respond to the survey questions at three random time points during the day. As a measure of physiological correlates of food consumption, glycemic responses will be monitored over a 15-day period using the FreeStyle Libre 3 device (https://www.freestyle.abbott/it-it/products/freestyle-libre-3.html), for continuous glucose monitoring (CGM). This tool collects real-time data on physiological changes in glucose regulation by measuring interstitial glucose levels every minute via a small sensor worn on the back of the upper arm. The sensor captures fluctuations in glucose throughout the day and night, providing detailed information on glycemic variability, postprandial responses, and potential episodes of hypo- or hyperglycemia.

All participants will be assessed through online self-report questionnaires at the end of the intervention (week 4) and follow-up (week 8). At all time points, weight will be measured. At 4- and 8-week follow-up, participants will complete a subset of the measures completed at baseline: Dutch Eating Behavior Questionnaire (DEBQ); Three Factors Eating Questionnaire (TFEQ); Food Cravings Questionnaire-Trait (FCQ-T); Eating Disorder Examination Questionnaire (EDE-Q); Binge Eating Scale (BES); Depression Anxiety Stress Scales Short Version (DASS-21); Work and Social Adjustment Scale (WSAS); Food liking and wanting; Food-related go/no-go task; Food-related temporal discounting task.

Intervention phase

Participants will be randomly assigned to either:

• The experimental condition (TAU + food-specific inhibitory training) or the control condition (TAU only).

All participants will be instructed to download the Food Tracker app and complete the EMAs for three days after the baseline assessment and three days after the 4-week assessment.

Participants assigned to the TAU+FoodTraining group will have access to the FoodTraning App following the baseline EMAs. They will be asked to complete a session once a day for the first week and three times a week for the remaining three weeks.

Participants in the control group will be offered access to the FoodTraining App at the end of the 8-week follow-up.

Access to the FoodTraining and FoodTracker Apps will be free of charge for participants.

Inclusion Criteria:

• BMI in the obesity range (>30) or a clinician-formulated diagnosis of binge eating disorder or bulimia nervosa;
• knowledge of Italian or English;
• access to a mobile device (e.g. smartphone, tablet).

Exclusion Criteria:

• visual impairment not corrected by glasses
• a diagnosis of psychosis;
• intellectual disability.

A plan will be established by the research team for data sharing following publication of the first manuscript

Each participant will be assigned an identification code (ID-code) randomly generated by a computer. The outcome assessors will be blind to whether participants will be assigned to the experimental or control group.