Intervention and evaluation protocol of fit4future Kids: A multi-component health promotion programme in German primary schools

Abstract Background: Schools are widely recognised as key settings for promoting childrens health behaviours. However, many schools struggle with the implementation and especially sustainment of health promotion programmes e.g. due to limited resources. Strengthening schools capacity for health promotion has therefore been identified as a central strategy for achieving better implementation and ultimately behaviour change outcomes among children. The fit4future Kids programme was developed as a large-scale, multi-component initiative in Germany that aims to promote childrens physical activity, nutrition, mental health, and responsible digital media use while simultaneously supporting schools in building structures for sustainable health promotion. Methods: This paper describes the intervention and evaluation protocol of the nationwide fit4future Kids programme implemented in several cohorts of German primary schools from Sept. 2022 to Sept. 2027. The intervention is based on the Health Promoting Schools framework and integrates established implementation and behaviour change frameworks, including the Consolidated Framework for Implementation Research, the COM-B model, and Behaviour Change Techniques. The programme combines curricular materials, environmental components, and structured implementation support to facilitate the integration of health promotion into everyday school practice. The evaluation follows a mixed-methods design involving multiple stakeholder groups, including school staff, parents, and children. Quantitative and qualitative data are collected to assess implementation processes, contextual factors, and programme outcomes. The large and diverse sample of 1,153 participating primary schools allows for the exploration of different implementation trajectories and the investigation of potential equity-related effects. Discussion: By combining evidence-based health promotion strategies with implementation science approaches, fit4future Kids provides a large-scale real-world example of how schools can be supported in implementing sustainable health promotion. The evaluation is expected to generate important insights into the implementation and potential effectiveness of multi-component school-based interventions and to inform future initiatives aiming to strengthen health-promoting school environments.