School-Based Obesity Interventions in The Metropolitan Area of Rio De Janeiro, Brazil: Pooled Analysis from Five Randomized Studies.

School-based studies, despite the large number of studies conducted, have reported inconclusive results on obesity prevention. The sample size is a major constraint in such studies by requiring large samples. This pooled analysis overcomes this problem by analyzing 5926 students (mean age 11.5 years) from five randomized school-based interventions. These studies focused on encouraging students to change their drinking, eating habits and physical activities over the one-school year, with monthly 1-h sessions in the classroom, culinary class aimed at developing cooking skills to increase healthy eating and attempts to family engagement. Pooled intention-to-treat analysis using linear mixed models accounted for school clusters. Control and intervention groups were balanced at baseline. The overall result was a non-significant change in BMI (body mass index) after one school year of positive changes in behaviors associated with obesity. Estimated mean BMI changed from 19.02 to 19.22 in the control group and from 19.08 to 19.32 in the intervention group (p-value of change over time= 0.09). Subgroup analyses among those overweight or with obesity at baseline also did not show differences between intervention and control groups. The percentage of fat measured by bioimpedance indicated a small reduction in the control compared to intervention (p-value= 0.05). This large pooled analysis showed no effect on obesity measures, although promising results were observed about modifying behaviors associated with obesity.