School-based obesity prevention intervention in Chilean children: effective in controlling, but not reducing obesity

To evaluate the effectiveness of a 12-month multicomponent obesity prevention intervention. Setting. 9 elementary schools in Santiago, Chile. Subjects. 6-8 y old low-income children (N = 1474).

Randomized controlled study; 5 intervention/4 control schools. We trained teachers to deliver nutrition contents and improve the quality of PE classes. We determined % healthy snacks brought from home, children's nutrition knowledge, nutritional status, duration of PE classes, and % time in moderate/vigorous activity (MVA). Effectiveness was determined by comparing Δ BMI Z between intervention and control children using PROCMIXED.

% obesity increased in boys from both types of schools and in girls from control schools, while decreasing in girls from intervention schools (all nonsignificant). % class time in MVA declined (24.5-16.2) while remaining unchanged (24.8-23.7%) in classes conducted by untrained and trained teachers, respectively. In boys, BMI Z declined (1.33-1.24) and increased (1.22-1.35) in intervention and control schools, respectively. In girls, BMI Z remained unchanged in intervention schools, while increasing significantly in control schools (0.91-1.06, P = 0.024). Interaction group ∗ time was significant for boys (P < 0.0001) and girls (P = 0.004).

This intervention was effective in controlling obesity, but not preventing it. Even though impact was small, results showed that when no intervention is implemented, obesity increases.