Supporting Weight Management (SWiM): Evaluating the effectiveness, equity and cost-effectiveness of using acceptance-based guided self-help to improve long term outcomes of weight management interventions

Background Clinically meaningful weight loss can be achieved cost-effectively through behavioural, pharmacological and surgical approaches and can reduce incidence and complications of type 2 diabetes (T2D).

However, to maximize benefits for patients, the NHS and society, we must reduce weight regain, which negatively impacts physical and mental health.

Working with people with lived experience of obesity and diabetes and health professionals, we developed a guided self-help programme (SWiM) that uses principles of Acceptance and Commitment Therapy (ACT) to address core psychological challenges of weight loss maintenance.

In a feasibility study, we demonstrated that SWiM was feasible and had potential to reduce weight regain and improve wellbeing.

Aims This research programme aims to 1) Provide robust evidence concerning the effectiveness, equity, cost-effectiveness and sustainability of SWiM following a range of UK-commissioned standard behavioural programmes for the prevention and treatment of obesity and T2D 2) Explore how SWiM could meet the needs of people trying to maintain weight loss following obesity medication or surgery.

Methods We will do this through 7 inter-related work packages (WP) co-produced with patients and stakeholders: WP1: Refine the SWiM intervention to increase engagement and widen access WP2: Co-produce an implementation plan for efficient and inclusive engagement.

WP3: Randomised controlled trial to compare SWiM with standard care in people (N=1844) who have completed a behavioural weight loss programme.

Outcomes will be measured remotely and will include weight, glycaemia, behaviour, mental health and wellbeing, and health care usage at 6, 12 and 24 months.

We will explore differential uptake, engagement and effectiveness by initial weight loss programme and demographic groups.

We will examine multi-level determinants of weight loss maintenance and establish a UK-based cohort to enable future studies to understand the determinants and impact of weight trajectories. WP4.

Mixed methods process evaluation, including longitudinal qualitative interviews with participants (N=60) and SWiM coaches, to understand what worked, for whom, how, why and in what contexts.

WP5: Health economic modelling to examine the long term physical and mental health impact and cost-effectiveness of SWiM, including differential cost-effectiveness based on initial weight loss programme and demographic groups.

WP6: Focus groups with people who have had bariatric surgery (N=20) and interviews with people who have finished obesity medication (N=20) to understand whether and how this intervention could be adapted to meet the needs of these groups.

WP7: Transferability assessment to understand how SWiM could be adopted for national roll out and the adaptations needed for specific contexts. Roadmap to scale up and national roll out.

Anticipated Impact and Dissemination We will disseminate our findings through scientific and professional journals and conferences and co-produced stakeholder-specific creative communication materials.

Our findings will help the government and the NHS decide whether and how SWiM should be commissioned to support weight loss maintenance in people who have taken part in behavioural programmes for obesity and type 2 diabetes. We will also produce new plans to develop and evaluate programmes to improve outcomes following medication and surgery.