Effectiveness of an Intervention in Reducing Weight Status Inequities in Primary Schools

Abstract Background Obesity is a major global health concern, with disparities most pronounced among socioeconomically disadvantaged groups. Despite policy efforts, inequities in childhood weight status persist. Addressing these requires interventions that not only promote healthy behaviors but also tackle upstream social determinants. Methods A cluster-randomised controlled trial was conducted in ten primary schools located in socioeconomically disadvantaged areas of Northern Portugal. A total of 735 children (6-12 years) participated. The intervention combined accredited teacher training, classroom activities, and family engagement. Data on BMI z-score, waist-to-height, and waist-to-weight ratios were collected at baseline, post-intervention (4 months), and follow-up (12 months). Analyses incorporated PROGRESS indicators (e.g., nationality, parental occupation, education, and social capital). Results At the 12-month follow-up, non-Portuguese children exhibited a significant reduction in waist-to-height ratio, indicating positive outcomes in a group typically at higher risk of health inequities. Boys also demonstrated a significant decrease in BMI z-score. Conversely, children whose parents held lower or higher white-collar occupations showed an increase in BMI z-score over the same period. These findings underscore the nuanced effects of the intervention across different social groups and highlight the complex interaction between social determinants and health outcomes. Conclusions BeE-school demonstrated positive impacts in specific vulnerable groups, supporting its potential for addressing childhood obesity inequities. Scaling up participatory, systemic school-based interventions could strengthen health promotion policies, particularly in disadvantaged communities. Key messages • School-based participatory interventions can reduce obesity risks among socially vulnerable children. • Social determinants and inequities significantly influence intervention outcomes, requiring tailored public health strategies.