Exploring the implementation of the school-based obesity prevention Familie+ intervention: a pilot mixed-methods study of teachers’ perceptions

Teachers play a pivotal role as implementers in school-based obesity prevention interventions. Given the influence of teachers' perceptions on the implementation process, the aim of this pilot study was to investigate the delivery of, ratings on, and influencing factors for the implementation of the school-based Familie+ intervention delivered in low socioeconomic regions in Germany. Building upon the Consolidated Framework for Implementation Research and the Implementation Outcomes by Proctor, we conducted a sequential mixed-methods study design. Delivery of the intervention activities, their ratings, and influencing factors were assessed using questionnaires and interviews at two time points. Deductive qualitative content analysis using Consolidated Framework for Implementation Research was applied to the interview data to support the questionnaire data. Mixed-methods data are jointly presented. Overall, delivery of the intervention varied, with the nutrition activities most often delivered. Teachers valued the intervention activities overall positively. The main factors influencing implementation were related to the intervention materials themselves (e.g. high complexity and limited adaptability) and procedures within the school (e.g. mixed compatibility with workflows). School-based interventions should incorporate principal engagement and strengthen cooperation within the school team. Flexible interventions with multiple options for adaptations should be provided.