Total diet replacements (TDRs) and weight loss medications (WLMs) have proven effective in producing substantial weight loss for individuals with obesity. Evidence is lacking on whether combining these treatments is effective and cost-effective in primary care for adults with obesity class I (body mass index (BMI) 30–34.9) or uncomplicated obesity class II or higher (BMI≥35 without obesity-related disease).

LightCARE is a 2-year 1:1 randomised, parallel-group, clinical superiority trial with blinded outcome assessment evaluating the benefits and harms of an intensive weight loss (IWL) intervention compared with usual care for adults with obesity in Denmark and the UK. The trial will include 400 participants aged 18–60 years with obesity class I or uncomplicated obesity class II or higher. The IWL programme aims to achieve and maintain a weight loss of ≥20% through a flexible and individualised combination of TDR, behavioural support, including physical activity and sleep guidance, and WLM if needed and will continue for 2 years. The control group will receive usual care offered in each country, typically consisting of brief behavioural support for weight loss. The primary outcome is body weight 2 years after randomisation. Secondary outcomes will include the proportion of participants achieving ≥20% weight loss, Short-Form-36 Mental Component Score, 4-m gait speed and Metabolic Syndrome Severity-Z score. Serious adverse events, the incidence of eating disorders and bone mineral density will be evaluated as safety outcomes. We will also examine the cost-effectiveness of the intervention, within the trial and in the longer term through modelling. We will conduct a process evaluation to inform any future implementation.

Ethical approval was granted in Denmark (December 2023, H-23051332) and the UK (August 2024, 24/SC/0210). Findings from the trial will be disseminated through peer-reviewed journals and scientific conferences.

NCT06321432.