Impact of a Randomized School-based Intervention on Sugar-sweetened Beverage Intake Substitution by Water to Prevent Excessive Weight in Mexican Scholars

This was a randomized community trial, that included children of both sexes belonging to public elementary schools, grades 4 and 5, in Hidalgo, Mexico, including the municipalities of Emiliano Zapata and Apan. It was excluded from school children with Type 1 Diabetes, heart failure, kidney or liver that limit fluid intake by medical prescription.

A sample size of 334 (167 in each group) children would allow to detect a difference of 9% in water consumption between the two groups15, considering a loss to follow-up of 20%, a power of 85% and a significance level of 0.05.

The selection of the schools of the two communes was based on the availability of a place to conduct physical assessments and intervention. Schools were randomly assigned to the intervention (IG) or control groups (CG). Each group included 3 classes of fourth grade and 3 classes of fifth grade.

Written informed consent was obtained from school principals, teachers, parents and students. The study was approved by the Ethics Committee of the Instituto Nacional de Ciencias Medicas y Nutrición Salvador Zubiran, in Mexico City.

Measurements Study variables were measured at baseline and at 6 months after intervention. Weight was measured with a portable scale (SECA professional scale model 750, Seca North America East, Hanover, MD) with a capacity of 150 kg and a precision of 1kg, height (SECA model 280 portable stadiometer, Seca North America East, Hanover, MD) with an amplitude of 220 cm and variation of 1 mm. Subjects were weighed and measured with minimal clothing and no shoes21. Body mass index (BMI) was calculated as weight (in kg) divided by stature2 (in m). Classification of nutritional status was based on z-scores of the BMI-for-age and sex from the distributions of the World Health Organization using the Anthro-Plus software22.