Overweight and obesity have become a global public health concern, with prevalence rising sharply in low- and middle-income countries. This study analyzed temporal trends in overweight and obesity among schoolchildren in the largest capital city of Brazil, from 2006 to 2024.

Repeated cross-sectional.

Schoolchildren aged 6 to 19 from Porto Velho, Rondônia, Brazil.

A total of 12,646 participants were evaluated. To assess the body mass index z-score, standardized body mass and height measurements were used, stratified by sex (male and female) and age group (6-10 and 11-19 years). Temporal trends were assessed using joinpoint regression analysis.

Overall, 17.8% of participants were classified with overweight, and 8.6% were classified with obesity. The study also found that obesity prevalence was consistently higher among younger age groups compared to adolescents. The results revealed a significant increase in obesity prevalence among girls (annual percentage change [APC] = 5.81%; 95% confidence interval [95%CI] = 1.03-10.81; p-value = 0.021) and children aged 6 to 10 years (APC = 5.20%; 95%CI = 1.17-9.39; p-value = 0.017), while no significant trends were observed for overweight or for male adolescents or adolescents aged 11 to 19 years.

Our findings indicate rising obesity among girls and children aged 6–10 and support the need for urgency. We recommend targeted action, including implementing mandatory quality physical education and school nutrition standards, enforcing restrictions on marketing to children, and prioritizing municipal policies that increase access to healthy foods.