Engaging Service Users in Co-Designing a Nurse-Led Weight Talk Tool for Low- and Medium-Secure Mental Health Inpatient Settings: A Participatory Intervention Development Study.

Approximately 80% of individuals in secure mental health units are overweight or obese, yet nurses often lack practical guidance on how to initiate and sustain weight-related conversations in these complex settings. This study aimed to co-design an evidence-based, nurse-led weight talk tool with service users and nursing staff, and to evaluate its acceptability and usability in low- and medium-secure inpatient care. A multi-stage, iterative design was undertaken. Initial evidence informed development, followed by a person-centred co-design process involving service users and staff through workshops, structured discussions and repeated feedback. The tool was subsequently evaluated using a think-aloud approach with 19 nurse-service user pairs, enabling real-time exploration of usability, understanding, and emotional responses. Co-design produced a structured, visually engaging tool tailored to the sensitivities and constraints of secure mental health settings. Service users and staff shaped key refinements, including simplified language, removal of potentially stigmatising elements, enhanced visual design, and the inclusion of structured opening and closing components to support psychologically safe conversations. Evaluation findings demonstrated high acceptability and usability. Service users valued the respectful, collaborative approach, while nurses reported increased confidence in addressing weight-related issues. These findings highlight the value of co-design as a method for developing acceptable, contextually relevant interventions for sensitive clinical topics. Embedding collaborative approaches within mental health nursing practice may strengthen therapeutic engagement and support more effective, person-centred care across diverse international settings.