Supporting Weight Management during COVID-19 (SWiM-C): A randomised controlled trial of an acceptance-based behavioural intervention to prevent weight gain during the pandemic

Introduction: The social distancing and isolation measures imposed during the COVID-19 pandemic mean that adults with overweight and obesity in the UK are at increased vulnerability to weight gain and the associated negative impacts on physical and mental wellbeing. There is growing evidence that interventions based on Acceptance and Commitment Therapy (ACT) are more effective for weight management compared with standard behavioural treatment. In collaboration with patient and public representatives and other stakeholders, we developed an ACT-based behavioural intervention to support adults with overweight and obesity to prevent weight gain during the COVID-19 pandemic (SWiM-C). This study evaluated whether SWiM-C reduced weight and achieved greater improvements in eating behaviour, physical activity and mental wellbeing compared with standard advice, over four months during the pandemic. Methods: We randomised adults (BMI≥25kg/m2) to the SWiM-C intervention or to a standard advice wait list control group. SWiM-C is an ACT-based guided self-help intervention consisting of weekly webbased sessions for 12 consecutive weeks, with two remote contacts (by telephone and email) from a trained non-specialist coach. The control group received standard advice from the European Association for the Study of Obesity (EASO) on diet, physical activity, and mental wellbeing during the COVID-19 pandemic. The planned sample size was 360 to give us 90% power to detect a 1kg difference between groups at the 5% level. Participants completed outcome assessments online at baseline and 4 months follow-up. The primary outcome was change in self-measured weight from baseline to four months;secondary outcomes included depression, anxiety, stress, psychological flexibility, eating behaviour (cognitive restraint, uncontrolled eating and emotional eating), physical activity, and health-related quality of life. Analysis was based on the intention-to-treat principle. We estimated baseline-adjusted differences between the study groups in change in weight (and secondary outcomes) from baseline to 4 months using linear regression models, also adjusting for randomisation stratifiers (sex, BMI group). Results: We recruited and randomised 388 participants (196 standard advice, 192 SWiM-C). 187 (97%) SWiM-C participants started the intervention, 167 (87%) completed the coach call, 161 (84%) were sent tailored coach emails, and 93 (48%) completed at least 8 sessions. Follow-up for the primary outcome was completed by 325 (84%) participants. Analysis of the effectiveness of SWiM-C is currently underway and will be completed before the conference. Conclusion: There is a need for user-friendly and remotely delivered weight management interventions to support adults with overweight and obesity during the COVID-19 pandemic. SWiM-C has demonstrated excellent uptake and engagement levels for a predominantly digital intervention, and we will report on the effectiveness of this approach. Findingswill inform the evidence base on digital interventions for weight management and can be used to inform existing services which are currently transitioning from face-to-face to online delivery.