Effectiveness of a health promotion program on overweight in vulnerable children from primary schools (BeE-school): A cluster-randomized controlled trial

Background: Obesity is a complex, multifactorial disease with rising global prevalence. Considering its significant association with lower socioeconomic status, implementing obesity prevention programs in vulnerable school-age children is particularly pertinent. This cluster-randomized controlled trial aims to evaluate the effectiveness of a health promotion program on overweight in vulnerable children from primary schools. Methods: The BeE-school study involved 735 children (51.7% boys, average age 7.7 (1.2) years old) from 10 primary schools in the Northern region of Portugal, identified as Educational Territories for Priority Intervention. After the initial assessment, the schools were randomized into two groups: one receiving the intervention (4 schools, n= 353) and the other not (6 schools, n= 382). The intervention included education and training teachers for 16 weeks, their implementation in the classroom, and giving families challenges every two weeks during this length of time. The program’s effectiveness was assessed short-term, immediately post-intervention (for 95.5% of participants) and long-term, one year after (for 50.8%). We considered the difference in BMI z-scores (BMIz), waist-to-height ratio and waist-to-weight ratio, from baseline to post-intervention and follow-up assessment. Results: In post-intervention, intervened children presented a significant reduction in all the three measures of adiposity: BMIz (B= −0.098, 95% CI: −0.156 to −0.040, p= 0.001), waist-to-height ratio (B = −0.007, 95% CI: −0.010 to −0.003, p< 0.001) and waist-to-weight ratio (B= −0.121, 95% CI: −0.193 to −0.048, p= 0.001). One year after the intervention ended the decrease in BMIz remained significant (B= −0.114, 95% CI: −0.213 to −0.015, p= 0.023). Conclusion: Conclusion: The school-based intervention, focusing on teacher training in health promotion and involving families, proved to be effective in improving body composition in socially vulnerable children.