The impact of weight loss programmes on disordered eating

The prevalence of obesity is increasing globally. Significant weight loss is an effective strategy to manage the condition, as well as manage conditions associated with obesity, like type 2 diabetes (T2D). However, alongside the prevalence of obesity and T2D, the prevalence of eating disorders is equally increasing globally. Eating disorders can be devastating for people who experience them, and they often co-exist with overweight/obesity and T2D, therefore offering weight loss treatments to this population could be considered risky. In 2020, NHS England announced the roll-out of the NHS Path to Remission programme for people living with overweight/obesity and T2D, which offered total diet replacement (TDR) targeted at significant weight loss and diabetes remission. Concerns on the impact of the programme on disordered eating emerged. The research in this thesis aimed to investigate the impact of weight loss programmes, including TDR, on disordered eating. I initially conducted a systematic review and meta-analysis to explore the impact of weight loss programmes, either alone or paired with psychological support intervention or pharmacotherapy on disordered eating scores, regardless of baseline disordered eating status. I found that weight loss programmes were associated with a consistent reduction in disordered eating in the end of the intervention and at a further follow-up. In sub-group analyses, disordered eating scores reduced more in people with an eating disorder at baseline compared with people without high scores, and there was no evidence the association depended upon intervention type. The review only identified two studies using more rigid interventions like low-energy diet replacement, where I hypothesised the risks would be greater. As a result, I designed and conducted a non-inferiority randomised controlled trial, investigating the impact of a TDR programme on disordered eating scores in people living with overweight/obesity, T2D and disordered eating at baseline. Disordered eating and its impairment reduced significantly in the intervention arm compared to the control group, and so did depressive symptoms and diabetes distress. No participant was judged to be at high suspicion for having developed a new eating disorder. I also analysed recordings of the dietetic sessions qualitatively, to identify similarities and differences in experiences of people participating in a TDR programme according to their disordered eating score trajectories. Participants with worsening disordered eating scores or of variable pattern of change throughout the trial reported eating usually in response to emotions and boredom, and experiencing significant hunger during the TDR phase, as well as a non-supporting environment. This often resulted in non-adherence and unsuccessful attempts to return to the programme. Participants who experienced stable or reducing disordered eating scores throughout the trial also experienced hunger but were often able to manage it and continue on the programme. Combining qualitative and quantitative data from this research, I concluded that weight loss programmes including TDR, are associated with reductions in disordered eating scores in the short term; longer term impact could be explored in future research.