Process evaluation of the IDEFICS school intervention: putting the evaluation of the effect on children's objectively measured physical activity and sedentary time in context

OBJECTIVES: The first aim was to describe the intervention implementation and reception with specific regard to physical activity (PA) within Belgian schools participating in the IDEFICS (Identification and prevention of Dietary‐ and lifestyle‐induced health EFfects In Children and infantS) intervention. Second, we examined if a higher intervention process score in schools showed more favourable effects on children's objectively measured PA and sedentary time (ST). METHODS: The IDEFICS intervention focused on improving children's health behaviour (including PA) at the community, school/kindergarten and family level. Five process evaluation questionnaires completed by school working groups, and (physical education) teachers were used for the process evaluation of four intervention modules (school working groups, healthy weeks, school environment, health‐related physical education and PA). Items were summed to calculate a total intervention process score per school. Schools were subdivided into three groups (low, medium and high score). Multilevel models were used to examine if changes in PA or ST differed between schools with a low, medium or high score. In total, 333 children (54.1% girls, mean age 6.0 ± 1.5 years) from 34 intervention schools (18 pre‐schools and 16 primary schools) in the town of Geraardsbergen, Belgium, provided valid accelerometer data for two weekdays and one weekend day. RESULTS: Mean intervention process score (maximum value = 44) was 20.9 ± 5.8 for schools. The breakdown per module showed which components were implemented and received well and which components could have been improved. After the intervention, the decrease in light PA and increase in ST was much higher in children from primary schools with a low intervention process score, whereas the behaviours remained relatively stable in children from primary schools with a medium or high score. The change in moderate to vigorous PA did not differ significantly between schools with a low, medium or high score. CONCLUSION: The IDEFICS intervention was relatively able to prevent unfavourable changes in ST and light PA in schools with a medium and high intervention process score. Further process evaluation research is needed to obtain a more profound picture of the IDEFICS intervention process.