In the United Kingdom, the National Institute for Health and Care Excellence make recommendations to guide the local-level selection and implementation of adult behavioural weight management interventions (BWMIs) which lack specificity. The reporting of BWMIs is generally poorly detailed, resulting in difficulties when comparing effectiveness, quality and appropriateness for participants. This non-standardised reporting makes meta-analysis of intervention data impossible, resulting in vague guidance based on weak evidence, reinforcing the urgent need for consistency and detail within BWMI description. STAR-LITE – a 4-section, 119-item standardised adult BWMI reporting template – was developed and tested using a two-phase process. After initial design, the template was piloted using adult behavioural weight management RCTs and currently implemented UK BWMI mapping information to further refine the template and examine current reporting and variance. Overall, reporting quality of weight management RCTs was poor, and large variance across different components of real-world BWMIs was observed. Non-specific guidance and wide variation in adult BWMIs are likely linked to inadequate RCT reporting quality and the inability to perform reliable comparisons of data. Future use of STAR-LITE would facilitate the consistent, detailed reporting of adult BWMIs, supporting their evaluation and comparison, to ultimately inform effective policy and improve weight management practice.