Authors' objectives: National Health Service England piloted a low-calorie diet programme, delivered through total diet replacement and behaviour change support via 1 : 1, group or digital delivery, to improve type 2 diabetes in adults with excess weight.

Authors' results and conclusions: Fifty-five per cent of service users who started total diet replacement completed the programme and lost an average of 10.3 kg; 32% of those with data available to measure remission achieved it. Examination of programme mobilisation identified barriers around referral equality and the impact of COVID-19, while effective cross-stakeholder working and communication were key facilitators. Service delivery and fidelity assessments identified a drift in implementation fidelity, alongside variation in the behaviour change content across providers. Perceived barriers to programme uptake and engagement aligned across service providers and users, resulting in key learning on: the importance of person-centred care, service user support needs, improvements to total diet replacement and the social and cultural impact of the programme. Early National Health Service quantitative analyses suggest some socioeconomic variation in programme uptake, completion and outcomes. Insights from the evaluation and National Health Service data were combined to develop the programme theory and underpinning context, mechanisms and outcomes. These were used to develop a list of recommendations to improve the cultural competency of programme delivery, total diet replacement delivery, peer support and address psychological support needs. Cost-effectiveness analyses using short-term follow-up data indicated there is potential for the programme to be cost-effective, but not cost saving. The National Health Service low-calorie diet can provide a clinically effective and potentially cost-effective programme to support weight loss and glycaemic control in adults with type 2 diabetes. However, this evaluation identified areas for improvement in referral equity, uptake and completion, and fidelity of delivery, which have informed the development of the programme, which has now been rolled out nationally. Ongoing programme monitoring and long-term follow-up are now required.

Authors' methods: A mixed-methods study underpinned by a realist-informed approach was delivered across five work packages, involving: semistructured interviews with service users (n = 67), National Health Service staff (n = 55), service providers (n = 9); 13 service provider focus groups; and service user surveys (n = 719). Findings were triangulated with clinical data from the National Health Service England’s first cohort analysis (n = 7540).

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hsdr/NIHR135898

Year Published: 2025

URL for published report: https://www.journalslibrary.nihr.ac.uk/hsdr/MPRT2139

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/MPRT2139

Organisation Name: NIHR Health Services and Delivery Research programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk