Rationale, aims and structure of the research programme
Rationale
Overweight and obesity is estimated to account for 4.6 million new cases of type 2 diabetes (T2D) in the UK by 2035.1 Intensive specialist-led behavioural weight management interventions that use recommended multicomponent strategies2 can prevent T2D in those at high risk3 and improve outcomes in those with T2D.4 However, few are sufficiently scalable to reach all who could benefit,5 and weight is typically regained after interventions end.6 Behavioural weight management interventions that use non-specialists (e.g. health trainers, community members) and digital technology can be delivered at scale at a relatively low cost. This research programme investigated whether scalable behavioural weight management interventions can achieve and maintain weight loss and reduce the incidence and complications of T2D in people at high risk of T2D and those with a recent diagnosis.
Scalable weight loss programmes for the prevention of type 2 diabetes in people at high risk
Systematic reviews show that intensive specialist-led behavioural interventions targeted at people with non-diabetic hyperglycaemia can reduce the incidence of T2D by 26%,3,7,8 with the US Diabetes Prevention Programme (US DPP) achieving 58% reduction over 3 years.9 However, specialist-led programmes are difficult to deliver at scale because of high implementation costs, a limited pool of specialists, and low uptake outside of trial settings.10 Commercial open-group behavioural interventions use many of the same effective strategies as specialist-led programmes,2,3 but are delivered in community settings by trained non-specialists and/or using digital technology to increase scalability and reduce costs. We have previously demonstrated their cost-effectiveness in people living with overweight or obesity,11–13 and a systematic review found these programmes were the only behavioural weight management programmes (BWMPs) with robust evidence that are currently commissioned for adults with obesity in UK primary care.5
Since we started this research programme, the NHS has started to deliver an NHS DPP that uses digital technology and non-specialists to enable scalability. Observational evaluation found that the NHS DPP is cost-effective in adults identified as having non-diabetic hyperglycaemia.14,15 Offering this type of scalable behavioural intervention to adults with overweight and obesity simplifies targeting of a high-risk group relative to screening for non-diabetic hyperglycaemia. Using data from a population-based cohort (N = 33,184), we showed that moderate weight loss (3–7%) in this population could prevent one in three diabetes cases over 10 years.16 Adults with overweight or obesity are also at higher risk of other physical and mental health conditions17–20 that mean weight loss through behavioural interventions could have wider public health impact beyond incident T2D.
In the Weight loss Referrals for Adults in Primary care (WRAP) trial,21 we showed that for people living with overweight and obesity, 52 weeks of weight watchers (WW) achieved 2 kg greater weight loss than brief intervention (BI) and 1.3 kg greater weight loss than 12-week WW over 2-year follow-up.22 The 52-week programme also achieved greater reductions in glycated haemoglobin (HbA1c) than brief intervention (−2.65 mmol/mol) or the 12-week programme (−1.31 mmol/mol) at 1 year (HbA1c was not measured at 2 years). Weight loss for the 52-week programme (7 kg at 1 year, 5 kg at 2 years) was similar to specialist-led intervention in the US DPP, which reduced incidence of T2D despite gradual weight regain.9 However, we cannot assume that weight and HbA1c following the 52-week WW programme would follow similar long-term trajectories given the longer duration and greater intensity of DPP and the different baseline population. WRAP was the first randomised controlled trial (RCT) of a scalable behavioural weight management intervention to follow participants beyond 2 years. In this research programme, we followed up participants from the WRAP trial to enable more precise measurement of the impact of this scalable internationally available behavioural weight management intervention on 5-year changes in body weight and glycaemia. We then used these data to undertake more realistic evaluation of long-term cost-effectiveness of this intervention and its impact on T2D and other health outcomes.
Scalable weight loss programmes for the treatment of type 2 diabetes
Bariatric surgery and new obesity medications can improve glycaemic control (and related risk factors) in people with T2D, leading to ‘remission’ and reduced risk of complications.23–28 There is also evidence from highly controlled studies that low calorie formula diets could achieve remission in T2D.29,30 This approach has been adopted by the NHS Remission programme, but availability is limited because of high costs and this intervention is not suitable or acceptable to all who might benefit from it. UK standard care for newly diagnosed T2D includes referral to structured diabetes education,31 which has small, short-term effects and relatively poor uptake.4,32–34
Intensive dietary intervention during the first year after diagnosis can achieve good glycaemic control35 and we have shown that behavioural changes in that first year can reduce likelihood of stroke or heart attack over 5 years.36 A systematic review found that lifestyle interventions (> 11 hours) have better outcomes for body mass index (BMI) and HbA1c than structured education (< 10 hours) without additional support.4 Integrating scalable behavioural weight loss programmes into care pathways for T2D could be a cost-effective way to improve glycaemic control and related risk factors and reduce complications.
In this research programme, we evaluated a new intervention that combined referral to WW with National Institute for Health and Care Excellence (NICE)-compliant diabetes education and remote dietetic support. In a RCT, a US version of this programme helped adults with T2D lose weight and achieve good glycaemic control.37 Twenty-four per cent of participants randomised to this programme reduced their HbA1c below 53 mmol/mol at 12 months, compared with 14% receiving standard care. However, a RCT was needed to provide robust evidence of cost-effectiveness in comparison to current UK standard care (structured diabetes education). We conducted the Glucose Lowering through Weight Management (GLoW) trial to evaluate the effectiveness and cost-effectiveness of diabetes education and behavioural weight management programme (DEW) in adults with a new diagnosis of T2D. We conducted a mixed-methods process evaluation to understand what worked, what did not and why and we evaluated the impact of this intervention on frequency of complications and health service costs over a lifetime perspective.
Improving weight loss maintenance for prevention and treatment of type 2 diabetes
The cost-effectiveness and long-term impact of behavioural weight loss programmes depends on post-treatment weight loss maintenance.38,39 Systematic reviews show that for most people weight is regained within 3–5 years, even after gold-standard specialist-led programmes.6,40 While existing programmes are effective for weight loss, a new approach is needed for weight loss maintenance. Extended use of traditional strategies (e.g. self-monitoring, problem solving) can improve weight loss maintenance.40 Trials have evaluated remote access/technology-supported versions of these.41 However, acceptance-based programmes that encourage people to experience aversive thoughts and feelings (e.g. daily challenges of weight control) without self-judgement, and act in line with desired goals and values, may be more effective at targeting determinants of weight loss maintenance.42–47 Acceptance-based programmes are typically delivered by psychologists, who are expensive and in limited supply. Cognitive–behavioural treatment for eating disorders and obesity can be delivered by non-specialists,48,49 but no trials have evaluated whether an acceptance-based programme delivered by trained non-specialists can improve weight loss maintenance. In this research programme, we developed an acceptance-based guided self-help programme Supporting Weight Management (SWiM) that is delivered using digital technology and non-specialist support to increase scalability and reduce implementation costs. We evaluated the feasibility and acceptability of this programme and we modelled the potential health economic impact of this intervention and the value of a definitive trial of cost-effectiveness.
Aims
- To develop and evaluate scalable behavioural weight management interventions that target determinants of weight loss and weight loss maintenance, and can be integrated into care pathways for the prevention and treatment of T2D.
- To inform practitioners and policy-makers about the impact of scalable BWMPs on the incidence of T2D, related complications and efficient allocation of NHS resources.
Structure
Figure 1 outlines the structure of the programme and how the work packages (WPs) feed into each other.
FIGURE 1 Work packages in this research programme. WP, work package. (Figure not reproduced here; see the original article.)
Work package 1 evaluated the effectiveness and cost-effectiveness of existing scalable weight loss programmes in two populations: (1) people at risk of T2D because of their higher BMI (WP1.1; WRAP 5-year follow-up) and (2) people who had had a diagnosis of T2D in the past 3 years (WP1.2; GLoW trial). Data from these trials were used to model the long-term health impact and cost-effectiveness of these interventions in these populations over a lifetime (WP1.3).
Work package 2 developed a novel scalable weight loss maintenance programme that could be used following existing weight loss programmes in both populations (WP2.1; SWiM) and evaluated its feasibility (WP2.2) in a RCT. It also evaluated the potential cost-effectiveness of SWiM and the value of conducting a definitive trial of cost-effectiveness (WP2.3).