Response to: Need for longitudinal evidence on child and adolescent nutrition in the Amazon.

We welcome the Letter to the Editor and their thoughtful commentary on our recently published study examining temporal trends in overweight and obesity among schoolchildren in Porto Velho, Rondônia, Brazil, from 2006 to 2024. We fully concur with their central argument: the evidence base on child and adolescent nutrition in the Amazon region remains heavily reliant on cross-sectional and repeated cross-sectional designs, with longitudinal cohort studies representing a critical and largely unmet need. Our own findings underscore the urgency of building the longitudinal infrastructure necessary to identify causal determinants of these trends. The Amazon basin, home to approximately 40 million people across nine countries and over 300 indigenous ethnic groups, presents a uniquely complex socio-ecological context marked by rapid urbanization, nutrition transition, environmental exposures, and profound structural inequities that cross-sectional evidence alone cannot adequately characterize. We endorse the authors' call for the prioritization of long-term longitudinal studies and, in particular, their vision of multi-center, transnational Amazonian cohorts supported by multi-country funding. We further propose that our established school-based surveillance infrastructure in Western Amazonia could serve as a meaningful foundation for future binational or multi-site collaborative research. We invite the authors to explore this possibility and look forward to contributing to a broader, coordinated research agenda aimed at improving child and adolescent health across the Amazon basin.