Impacto da Regulamentação do Ambiente Alimentar Escolar: aspectos metodológicos e participação no primeiro ano de acompanhamento

This article describes the methodological aspects and characterizes participation in the first year of the Impact of School Food Environment Regulation study. The study aims to monitor the commercialization of foods in canteens and the surrounding areas of private schools in three Brazilian cities with distinct regulatory contexts, as well as to investigate students' perceptions of the school canteen. It is a repeated cross-sectional study (2023/24 and 2025) with independent samples, conducted in Recife (PE), Niterói (RJ), and Porto Alegre (RS). For the Canteen Module, a stratified sampling of private elementary and high schools was planned, considering school size and using inverse replacement. The Street Vendor Module used a convenience sample, while the Student Module employed a three-stage cluster sampling. The first two modules replicate the methodology of the Commercialization of Food in Brazilian Schools (Caeb) study. The first data collection occurred between September 2023 and May 2024, involving 202 schools and 532 students. Only three street vendors were found. School participation rates were 47.8% in Porto Alegre, 53.9% in Niterói, and 69.9% in Recife. Schools' reluctance to participate in the study prolonged the data collection period and required methodological adaptations. This article discusses the challenges in fieldwork and the methodological adjustments planned for the second year of follow-up, offering recommendations for future studies in the school environment. This project results from a collaboration between academia and organized civil society, which sought information to support advocacy efforts for healthy eating in schools. The evidence generated may contribute to the development and improvement of policies aimed at protecting the school food environment in other cities and at different government levels.