[Effect of "Super 8 Law" implementation on body composition of schoolchildren during the National Holidays in Chile. Longitudinal-ecological study].

Introduction: several public health programs are being implemented to combat childhood obesity in the world. However, the impact of Chilean Law n.degrees 20,606, which regulates the sale and advertising of foods high in critical nutrients ("Super 8 Law") about a critical period in the increase of body weight in schoolchildren, such as National Holiday (NH), has not yet been evaluated. Objective: establish the effect of NH on various body composition indicators before and after the implementation of the Super 8 Law. Methods: 110 schoolchildren between 10 and 13 years of age participated in this study, and 48 finished it after one year of follow-up (23 children and 25 girls). Body weight, body mass index (Zscore-BMI), triponderal mass index (TMI), fat mass index (FMI), percentage of fat mass and muscle mass during the four weeks of September 2015 (without law) and 2016 (with law). An ANOVA for repeated measures and adjusted for covariates was applied. Results: body weight (0.327 and 0.556 kg), Zscore-BMI (0.057 and 0.085) and fat percentage (0.1 and 0.9%) increased significantly during both NH (without and with law, respectively). Compared to 2015, FMI and TMI do not show significant increases during 2016, however, there are no significant differences in any of the variables studied after the implementation of the law. Conclusion: despite observing slight advances in certain parameters of body composition between one year and another, the implementation of the Super 8 Law in Chile does not seem to generate a preventive effect during NH.