Evaluation of the NHS England Low-Calorie Diet implementation pilot: a coproduced mixed-method study.

Area of Science:

• Public Health
• Health Services Research
• Behavioural Science

Background:

• The National Health Service (NHS) England piloted a low-calorie diet program using total diet replacement and behavior change support for adults with excess weight and type 2 diabetes.
• Delivery methods included 1:1, group, or digital formats to improve health outcomes.

Purpose of the Study:

• To conduct a qualitative and economic evaluation of the NHS low-calorie diet pilot.
• To understand long-term cost-effectiveness, implementation, equity, and transferability across diverse populations.

Main Methods:

• A mixed-methods study using a realist-informed approach.
• Included semistructured interviews (n=67 users, n=55 staff, n=9 providers), focus groups (n=13), and user surveys (n=719).
• Findings were triangulated with NHS clinical data (n=7540).

Main Results:

• 55% of users completed the program, averaging 10.3 kg weight loss; 32% achieved type 2 diabetes remission.
• Barriers included referral inequality and COVID-19; facilitators were cross-stakeholder collaboration.
• Implementation fidelity varied, with identified needs for person-centered care and improved total diet replacement delivery.

Conclusions:

• The NHS low-calorie diet program is clinically effective and potentially cost-effective for weight loss and glycemic control in type 2 diabetes.
• Identified areas for improvement include referral equity, uptake, completion, and delivery fidelity.
• Recommendations informed national rollout, with ongoing monitoring and long-term follow-up needed.