Inhibitory Control Training for Excess Weight: Behavioural, Cognitive and Anthropometric Changes

People with excess weight (EW) are characterized by high impulsivity, high levels of craving for high-calorie foods, deficits in inhibitory control, and maladaptive decision-making. The proposed intervention seeks to target these issues. Thus, the present study aims to determine the effectiveness of combining inhibitory control training with usual treatment (diet and physical exercise) in treating people with EW to produce cognitive, behavioral and anthropometric changes. Participants will be randomly allocated to one of two groups: 1) the experimental group that would receive active inhibitory control training and (2) the active control group that will receive placebo inhibitory control training. Both groups will receive individualized diet and physical exercise guidelines. Training requires to inhibit responding to certain foods presented during computerized tasks. Using a food Go/No-Go paradigm, individuals are asked to press a button when a Go cue is presented next to an image and to refrain from pressing a button when a No-Go cue (e.g., a bold frame) is presented. In the experimental group, pictures of healthy and unhealthy foods are always paired with the Go and the No-Go signal, respectively whereas in the control group healthy and unhealthy foods are paired 50% of the time with the Go and 50% with the No-Go signal. It is hypothesized that the experimental intervention would be effective improving (i) Body Mass Index (BMI), (ii) food craving, (iii) anthropometric measures (waist circumference and waist-to-hip and waist-to-height ratios), (iv) eating and physical exercise behaviors (decreased caloric intake and increased frequency and time of physical activity), (v) emotional symptoms and emotional eating (depression, anxiety, emotional regulation, emotional eating, reward-related eating, non-homeostatic eating), and (vi) cognitive abilities (motor and cognitive inhibition, delay of gratification, impulsivity, working memory, cognitive flexibility and decision making).

1. HYPOTHESIS: Inhibitory control training with the food Go/NoGo paradigm will be effective in treating people with EW. Thus, the active intervention, compared to the placebo, will achieve: (i) decreased BMI, (ii) decreased craving, (iii) improved anthropometric measures (waist circumference and waist-to-hip and waist-to-height ratios), (iv) improved eating and exercise behaviors (decreased caloric intake increased frequency and time of physical activity), (v) improved emotional symptoms and emotional eating (depression, anxiety, emotional regulation, emotional eating, reward-related eating, non-homeostatic eating), (vi) improved cognitive abilities (motor and cognitive inhibition, delay of gratification, impulsivity, working memory, cognitive flexibility and decision making).

   GENERAL OBJECTIVE: To determine the effectiveness of inhibitory control training for the treatment of people with EW (improvements in BMI, craving, anthropometric measures, food and physical exercise behaviours, emotional symptoms and emotional eating, and cognitive measures).
2. METHODOLOGY

   2.1. Design: Randomized controlled trial of parallel groups. The sample size calculation was performed with the G\*Power 3.1 tool. To do so, it will be relied on the only study to date that applied food Go/NoGo training (4 sessions in one week) on a median effect size for reducing BMI post-treatment (Cohen's d = 0.57) and at 6-month follow-up (Cohen's d = 0.48). Thus, considering a median effect size for conducting ANOVAs (f= 0.25), the minimum recommended N to reach a power of 0.80, assuming an alpha level of 0.05 with two groups and three repeated measures, was 44 participants, 22 per group. Nevertheless, a conservative approach will be adopted and decided to increase groups to 27 participants.

   The participants (N=54) will be randomly allocated to two groups: (i) experimental group (active inhibitory control training); n=27 and (ii) active control group (placebo inhibitory control training); n=27).

   2.3. Interventions

   Pre-treatment sessions: information, dietary plus physical guidelines (all groups):

   First, all participants will participate in a group briefing informational session about the procedure and rationale of the study that will last about an hour. Also, informative videos and brochures will be provided. There will be two 90-minute sessions afterwards given by a nutritionist and personal trainer respectively to provide individualized diet and physical exercise instructions to all participants.

   Cognitive interventions (both groups): Duration: 2 weeks in which participants should train from monday to friday for 10 minutes with the active or the placebo version of the Food Trainer App (FoodT) with their smart phones.

   2.4. Outcome measures: change in Body Mass Index (BMI) will be the main outcome measure. Secondary outcomes will be changes in food craving, anthropometric measures, eating and physical activity behaviours, emotional symptoms and emotional eating, and cognitive measures. Screening and descriptive measured will include a sociodemographic questionnaire, depression and anxiety questionnaires, motivation and questionnaire on Eating and Weight Patterns-5.
3. PROCEDURE The whole study will be delivered online. Inclusion and exclusion criteria will be checked through the data collected in a questionnaire of sociodemographic and clinical variables. Further, psychopathology exclusion criteria will be tested with three questionnaires to measure depression, anxiety, and stress symptoms as well as binge eating and bulimia (BDI, DASS-21 and QEWP-5), and a short clinical interview by phone and/or information requested by email in those cases where there are doubts about any of the aspects collected through the online instruments.

All candidates who meet the criteria will attend an information meeting about the project in which participants will receive written and oral information and will be asked for their informed consent. Then, participants will be randomly assigned to groups before the pre-treatment assessment sessions. Both groups of the study (experimental and active control) will complete pre and post assessments, as well as the 3-month follow-up (see below). What will differentiate the groups will be, therefore, the treatment: active vs. placebo inhibitory control training. If at the end of the project the active training has proven to be effective, the control group will be offered the possibility to carry out the active training.

All sessions will be developed in groups of 4-6 people. There will be at least 5 groups of intervention sessions (27 participants) and 5 groups for the placebo condition (27 participants). The program will comprise 6 weeks including three assessments (pre, post and 3-month follow-up), two FoodT training weeks, as well as the information and nutrition and exercise sessions. Assessment sessions will last about 2 hours each while the inhibitory control training will last 10 minutes per day.

1. Informative session (session 1; week 1): For the participants to understand the foundation of the intervention information about the aims, basis of the project and the procedure of the research will be given. Participants will be provided written informed consent as well. At the end of this session, participants will be asked for their informed written consent.
2. Pre-treatment assessment (session 2; week 2): All participants will complete the following instruments to assess the main and secondary outcomes, and the exploratory and economic measures: WCST, Food Go/NoGo, IGT, Stroop, Food DD, N-Back, FCQ-S-r, CFA, IPAQ, DASS-21, BDI-II, PEMS, RED, DEBQ, PSRSQ, ERQ, UPPS-P, SF-36, SOCRATES 00, QEWP-5, sociodemographic questionnaire, another one about used health resources, stigma and previous treatments questions.
3. Nutrition and exercise sessions (session 3; week 3): Participants will receive information on healthy nutritional (Ph.D. Nutritionist) and physical exercise (Ph.D. Sports Science professional) habits. In addition, participants will receive individualized diet and physical exercise guidelines, and participants will be able to consult any doubts to both professionals through WhatsApp groups.
4. Training sessions (sessions 4 to 14, weeks 4 and 5): A daily reminder will be sent by WhatsApp to the participants' phone to train from Monday to Friday during 10 minutes for two weeks. The FoodT app will be used to pair high-calorie meals with the no-go cue. Images can appear on the left, right or center of the screen, and should be tapped or not depending on whether the image has a green or red circle around them. Participants earn points for correct tapping responses and lose points for incorrect tapping responses and must respond as quickly and accurately as possible. The placebo FoodT has images of objects rather than food.
5. Post-treatment assessment (session 15; week 6): To evaluate the effectiveness of the interventions, BMI and the following instruments will be administered to obtain the main and secondary outcomes: FCQ-T/S-r, WCST, Food Go/NoGo, IGT, Stroop, Food DD, N-Back, CFA, IPAQ, DASS-21, BDI-II, PEMS, RED, DEBQ, PSRSQ, ERQ, UPPS-P, SF-36, and a questionnaire about used health resources.
6. Follow-up (session 16; week 18): Follow-up at 3 months after the intervention will include the following measures: FCQ-T/S-r, WCST, Food Go/NoGo, IGT, Stroop, Food DD, N-Back, FCQ-S-r, CFA, IPAQ, DASS-21, BDI-II, PEMS, RED, DEBQ, PSRSQ, ERQ, UPPS-P, SF-36 and a questionnaire about used health resources. Anthropometric measures will be repeated as well. Every month after the end of the treatment, participants will be contacted by email and mobile message to maintain adherence.

Eligibility Criteria:
Inclusion Criteria:

* BMI between 25 and 39.9
* Age between 18 and 60 years
* Proficiency in the Spanish language
* Internet access
* Computer and smartphone

Exclusion Criteria:

* Traumatic, digestive, metabolic or systemic disorders that affect the central nervous system, autonomic or endocrine
* Severe psychopathological disorders, moderate depressive symptoms or treatment for depression
* Eating disorders