Evaluation of the feasibility and acceptability of a novel scalable behavioural weight loss maintenance programme
In this WP, we conducted a RCT to test the feasibility and acceptability of our SWiM weight loss maintenance programme, minimise uncertainties about trial parameters and inform the design of a definitive trial.
Rationale
In WP2.1, we developed a digital guided self-help intervention which draws on ACT-based principles to support weight loss maintenance following completion of a standard behavioural weight management intervention. Before conducting a trial to determine the effectiveness and cost-effectiveness of this intervention, we needed to evaluate the feasibility of delivering this programme using trained non-specialists in a community setting and the acceptability of this intervention for people living with obesity who had recently completed a standard behavioural programme. We also needed to evaluate the value and feasibility of conducting a full-scale RCT, in order to inform the design of that trial and an application for funding for further development and evaluation.
Objectives
To evaluate the feasibility and acceptability of the SWiM intervention by:
- examining participant experiences and views on acceptability, their patterns of use, facilitators and barriers to use, and the extent to which it met their needs
- examining implementation in terms of fidelity, dose, and reach and barriers and facilitators to delivering the intervention as intended
- qualitatively exploring the hypothesised causal mechanisms of SWiM and any unexpected mechanisms.
To evaluate the feasibility and value of a full-scale trial by:
- examining recruitment and randomisation procedures, recruitment and retention rates, and systems for data collection and outcome assessments
- describing changes in outcome variables and estimate variance to inform the design of a full-scale trial.
Method
This was a pragmatic single centre, two-arm, parallel-group RCT. An embedded qualitative study enabled mixed-methods process evaluation to understand what worked, what did not and why. The trial was pre-registered at ISRCTN12685964. The protocol is published in Ahern et al.,71 and the findings are published in Jones et al.72
We recruited 61 people who had recently completed a behavioural weight management intervention and randomised them to SWiM or local standard care (a leaflet about weight loss maintenance) in a 2 : 1 allocation. At 6 months, we measured changes in weight, eating behaviour and mental well-being. We also assessed perceived usefulness and ease of use of the SWiM programme. At 3 (mid-intervention) and 6 months (post-intervention), we conducted interviews with participants from both trial arms and SWiM coaches who also completed post-coach call reports. We used statistics and qualitative thematic analysis, guided by the MRC framework for process evaluations, to identify what worked, what did not work and why.
Key findings
Eighty-eight per cent (36/41) of participants allocated to SWiM completed at least the first session and 22 (54%) completed all sessions. Participants rated SWiM as easy to use, useful and enjoyable. They described how SWiM reinforced prior knowledge and taught new skills that supported long-term weight management. Average pre-trial weight loss was 8 kg. Between baseline and 6 months, SWiM participants lost a further −2.2 (SD 6.4) kg while control participants gained 2.2 (SD 6.6) kg (Figure 4). SWiM participants reported improvements in eating behaviour and mental health and reductions in experiential avoidance (i.e. increased acceptance, a key target mechanism); control participants did not.
FIGURE 4 Mean (standard error) change in outcomes between baseline and 6 months by intervention group in the SWiM feasibility study. (Figure not reproduced here; see the original article.)
Strengths and limitations
This trial was conducted remotely because of the challenges of the COVID-19 pandemic and weight outcomes were self-measured at the time of survey completion. Self-reported weight may be under-reported and less accurate than objectively measured weight,73 but it is similar to smart scales providing direct self-measurements.74 To increase the accuracy of self-reports, we provided clear, specific instructions to participants. The RCT design also mitigates against potential under-reporting as it is likely that under-reporting would be similar in both groups.
The majority of participants in this study were White and female. Lack of diversity is common within behavioural weight management trials,75,76 and in this study we will have inherited some of this because recruitment was restricted to those who had already completed a weight management programme. However, lack of diversity limits the generalisability of the study findings to other demographic groups and future evaluation studies should coproduce strategies to increase the diversity of the participants recruited.
Conclusions
This study found that the SWiM intervention was acceptable and feasible following a BWMP. Qualitative and quantitative findings also suggest that SWiM has the potential to improve weight loss maintenance and benefit both physical and mental health in the longer term. We identified areas for refinement which will inform future intervention development and design of a full evaluation.
Interrelation to other work packages
This WP evaluated the feasibility of the intervention developed in WP2.1 and provided data to inform the WP2.3 evaluation of likely cost-effectiveness and the value of conducting a definitive RCT.