Design of a school randomized trial for nudging students towards healthy diet and physical activity to prevent obesity

OBJECTIVE To evaluate the effectiveness of nudge activities at school on the students' body mass index (BMI). DESIGN School-based factorial randomized community trial. SETTING Eighteen public schools in the municipality of Duque de Caxias, metropolitan area of Rio de Janeiro, Brazil. PARTICIPANTS AND INTERVENTION The 18 schools will be randomized into 4 group arms: group 1-control (without any activity); group 2-will receive educational activities in the classroom; group 3-will receive changes in the school environment (nudge strategies); group 4-will receive educational activities and changes in the school environment. Activities will occur during the 2018 school-year. MAIN OUTCOME MEASURE(S) The primary (BMI) and secondary (body fat percentage) outcomes will be assessed at baseline and after the study using a portable electronic scale with a segmental body composition monitor. The height will be measured by a portable stadiometer. ANALYSIS Statistical analyses for each outcome will be conducted through linear mixed models that took into account the missing data and cluster effect of the schools.