Supplementing a widely available weight loss program with gamified inhibitory control training: A randomized pilot study

Abstract Background Increasing evidence suggests that targeting self‐regulatory processes may improve obesity treatment outcomes. Incorporating gamification principles in inhibitory control training may promote sustained training adherence and resulting benefits. This pilot study evaluated the preliminary efficacy of supplementing an evidence‐based weight management program (WW) with sustained gamified inhibitory control training (PolyRules!) on change in Body Mass Index (BMI) among adults with overweight/obesity. Methods 30 adults with overweight/obesity (M age 49.9 ± 12.4, 86.7% female; 23.3% Hispanic, mean BMI 35.3 ± 6.3) were randomly assigned to receive WW with or without PolyRules! for 12 weeks. The primary outcome was change in BMI from baseline to post‐intervention across study arms. Implementation and process indicators were captured to inform larger trials. Results Average change in BMI was −0.9 in the WW arm and −1.2 in the WW + PolyRules! arm (Cohen's d = 0.26). In the WW + PolyRules! arm, increased training was associated with greater decreases in BMI (r = −0.506, p = 0.0454). WW + PolyRules! participants completed an average of 60.4% sessions and reported positive experiences. There was no difference in frequency of food (d = −0.02) and weight tracking (d = −0.19) between arms. Conclusions Studies in larger samples should evaluate training‐related effects on weight. Supplementing WW with gamified inhibitory training appears feasible, with no detrimental effect on engagement.


| INTRODUCTION
In recent years, there has been an increased interest in understanding how cognitive and behavioral processes involved in inhibitory control may help explain heterogeneity in obesity treatment outcomes. [1][2][3][4] Inhibitory control describes the ability to actively inhibit or delay a dominant response to control one's attention and/or goal-oriented behavior, thereby withholding an automatic or prepotent response. 5 Studies have found relationships between deficits in executive functioning and obesity, 4,6-10 and there is evidence that poor inhibitory control may be associated with unhealthy eating, 11 unsuccessful dieting, 12 obesity and weight gain. 13,14 These findings lead to the puzzling question of whether impulse control training confers benefits in the context of weight management. [14][15][16][17] Initial findings suggest that inhibitory control training may increase self-regulation in the context of health behaviors. 14,18,19 Interventions based on the Go/No-Go task, a methodology for studying and training inhibitory control by challenging individuals to withhold dominant responses, have been shown to improve short-term eating regulation and produce modest weight-loss. 17,20 However, the transfer of inhibitory control training gains have been a source of skepticism. 21 These controversies may stem from previous studies' key limitations such as limited dosage and training duration (e.g., <10 training sessions over 2 weeks), exposure to a small set of stimuli, and lack of tailoring to participants' proficiency as the training progresses.
The efficacy of these interventions in terms of producing ecologically-valid improvements is also unclear. [22][23][24][25] To address the rigor of previous research, the Brain Game Center team has developed a novel inhibitory control training game (PolyRules!), which incorporates stimuli and task structures previously applied in visual perceptual learning and working memory training. 26,27 PolyRules! adjusts to users' inhibitory control proficiency [28][29][30] and incorporates gamification principles to sustain training frequency, duration, and promote adherence. 31 Research indicates that gamification, if applied properly, may lead to increased enjoyment and greater training adherence and benefits. 26 The present study examined the preliminary efficacy of supplementing a weight-loss program (WW, formerly Weight Watchers©) with gamified inhibitory control training (PolyRules!) on Body Mass Index (BMI) change among adults with overweight or obesity. Implementation and process indicators (participants' enrollment and attrition, adherence to and experience with WW components and inhibitory control training) were also captured to inform a larger trial, and to evaluate whether the addition of sustained inhibitory control training decreased engagement in WW components (daily dietary monitoring and weekly weigh-ins). The study team hypothesized that participants randomized to complete both WW and PolyRules! would report a greater change in BMI than participants randomized to WW alone. Further, it was hypothesized that combining WW and PolyRules! would not be unduly burdensome for participants.

| Study design
This study was a pilot, two-arm, randomized control trial comparing WW alone to WW with gamified inhibitory control training on change in BMI between baseline and post-intervention.
Participants were block randomized with replacement by study staff to ensure that the two arms had similar demographic characteristics.

| Procedure
Due to COVID-19 restrictions, all research procedures were conducted and facilitated remotely by study staff. Interested individuals were screened over the phone to determine if they met the eligibility criteria. Interested and eligible individuals were asked to provide written consent through DocuSign. After providing written consent, participants were randomized by study staff to one of two study arms (WW only or WW + PolyRules!) using a previously generated randomization scheme. If a participant prematurely withdrew from the study, another participant was recruited to maintain the final analytic sample of 30. The new participants were not automatically assigned to the same condition, but rather randomized based on the original randomization scheme.
Participants who did not have a personal iPad were provided with one for the duration of the study to standardize access to the WW program and the PolyRules! game. At baseline, participants completed a demographic and medical history questionnaire. Participants also completed a cognitive battery pre-and postintervention, and interactions with the WW program (daily food intake and weekly weight) and PolyRules! (training frequency) were continuously recorded to monitor engagement.  32 Although WW instructs participants to log their daily physical activity and permits syncing with smartwatches or similar devices, this data was not extracted in the present analysis because the food-specific inhibitory control training tested in this study was hypothesized to operate on self-regulatory processes most relevant to food intake. WW is the most studied and used commercial weight-management intervention, and the #1 doctor recommended program based on a 2019 survey by Kantar Health of 500 doctors.
Both the in-person and digital WW program have helped users achieve clinically significant weight loss of 5% of initial body weight. 33,34 WW + inhibitory control training (PolyRules!). In addition to WW, participants randomized to the gamified inhibitory control training arm were instructed to play PolyRules! 35 (Play experience illustrated in Figure 1). PolyRules! is an inhibitory control training application designed by the authors that combines elements of the Go/No-Go paradigm and rule switching tasks to train different aspects of cognitive functioning, including inhibitory control, attention and memory. For the present pilot study, neutral stimuli were supplemented with food-stimuli that participants were asked to respond and withhold responses to. Impulse control was conceptualized as a   ipants who prematurely withdrew from the study/total enrolled participants). Participants were considered to have withdrawn from the study if, at any time over the course of the study, they expressed that they did not want to continue the intervention and/or complete the remaining assessments.
Qualitative indicators were assessed through a semi-structured interview with all participants at the end of the 3-month intervention. These interviews were conducted using Zoom or MS Teams, audio-recorded and transcribed using a non-verbatim approach. Interviews were analyzed using focused coding and yielded themes of motivation, facilitators and barriers of adherence, and participant satisfaction.

| Data analysis
All statistical analyses were performed using SPSS 24 and SAS version 9.4 (SPSS Inc., Chicago, IL; SAS Institute Inc., Cary, NC). An a priori sample size calculation was not conducted due to the feasibility nature of this pilot study. 43,44 Descriptive statistics including frequencies, percentages, means and standard deviations were used to characterize the sample. Cohen's d effect sizes were calculated when appropriate. Differences between baseline and post-intervention continuous measures were tested using the paired t-test or Wilcoxon signed-rank test and differences between intervention arms were assessed using an independent sample t-test or Wilcoxon rank sum test, as appropriate. Spearman correlations were calculated to examine associations between the magnitude of change in BMI and adherence to WW (dietary intake tracking, weigh-ins) and PolyRules! components (trainings completed). Participants who withdrew from the study were replaced to maintain the final analytic sample of 30 participants. All participants, regardless of whether they completed all assessment timepoints, were included in the analyses. Given that this was a pilot trial, outcomes were interpreted for potential clinical significance based on the direction and magnitude of numerical differences.

| RESULTS
The CONSORT diagram is illustrated in Figure 2. Of the 119 individuals who contacted the study team, four ultimately declined to participate. Two of those individuals had enrolled in other weight management programs, and two were no longer interested in participating in the study. Because the enrollment was capped at 30 participants, 81 individuals had to be waitlisted for future studies.
Due to few exclusionary criteria, all interested individuals who were screened to participate in the study were eligible to participate.
Among participants who were consented in the study, four prematurely withdrew before treatment. Three of the participants who withdrew were randomized to the WW + PolyRules! arm, and one participant was randomized to the WW only arm. Two participants withdrew because they felt they could not commit to the study (WW + PolyRules!), while another participant withdrew because of the assigned study arm (WW only). One individual never actively withdrew from the study but failed to initiate the intervention and complete the study assessments (WW + PolyRules!). Table 1 summarizes the demographics of the final analytic sample.  In the post-intervention interviews, several themes were identified, with the primary being a positive experience with the study procedures and the inhibitory control training. The colors, shapes, and sounds of PolyRules! were described by participants as enjoyable, fun, and easy to play. A secondary theme identified was the perceived benefits of inhibitory control training. Participants felt that the inhibitory control training helped with weight loss, with one reporting it "helped me become more aware of unhealthy foods"). Other frequently cited perceived benefits from using PolyRules! were in terms of improved attention to details, concentration, focus, and memory. In the third and final theme, app dislikes and suggested improvements, participants described some of the features of the app that they disapproved of and felt could be improved. Some participants noted the lack of variety in food pictures, while others -779 mentioned that the instructions were sometimes ambiguous. Others mentioned that the appearance and clarity of the food images could be improved.

| DISCUSSION
This pilot study examined the preliminary efficacy and overall feasibility of supplementing an evidence-based, widely available weightmanagement program with gamified inhibitory control training among adults with overweight or obesity. Although the intervention period was fairly short by weight management standards, 44% of WW + PolyRules! participants and 31% of WW alone participants lost >1.5 BMI points over the 3-month study. On average, participants assigned to the combined arm (−1.2 BMI points) lost slightly more weight than participants assigned to WW alone (−0.9 BMI points), but this difference did not reach statistical significance.
Importantly, the addition of daily impulse control training did not seem to unduly burden participants in decreasing their engagement with dietary and weight monitoring. The enthusiastic response to recruitment material was also encouraging, with 119 individuals who contacted the study team within 5 weeks. Only a few individuals prematurely withdrew from the study, and most enrolled participants completed all study procedures. Adherence to WW and PolyRules! was also high, suggesting that participants were able to carry out the remote interventions simultaneously.  Akin to other pilot studies, this work includes several limitations related to the small and homogeneous sample of participants. Individuals who took part in the study were highly educated, affluent and 86.7% were women. The length of the intervention was also fairly short by weight management program standards.
Another key limitation of this pilot study is the reliance on selfreported anthropometric data. The financial resources and staffing allocated to this study precluded purchasing of electronic scales or scale drop off, especially considering the vast geographical area (4753 square miles) where participants were recruited. Ultimately, self-report was utilized in this pilot study to inform the refinement of procedures for a larger study. Although potential biases were minimized due to randomization, future studies using more rigorous methods to capture objective anthropometric data are needed.
It is also important to acknowledge that participants randomized to the WW only group were not assigned a control training condition.
Conceivably, structured/prescribed time allocation to a distracting activity incompatible with eating may enhance weight management efforts regardless of whether the activity targets inhibitory control.
This hypothesis is consistent with research on distraction and inhibitory control. 48  Diniz to conduct statistical analyses. All authors read and approved the final manuscript.

ACKNOWLEDGMENTS
The authors would like to thank Dr. Tiffany Bullard for coordinating WW membership distribution and contributing to data extraction, as well as the participants for participating in the study. The deidentified datasets, protocol and statistical plan from this study will be available from Dr. Salvy upon written request. This project is

CONFLICT OF INTEREST
Gary D. Foster is the Chief Scientific Officer at WW International, Inc., and is a shareholder. All other authors declare that they have no competing interests to disclose.

AND CONSENT TO PARTICIPATE
The protocol for this study has been approved by the Cedars-Sinai Medical Center Institutional Review Board (STUDY00001164) and is registered with ClinicalTrials.gov (NCT04747886). Participants were asked to provide consent to participate in the study.