This is a cluster randomized controlled trial. The study will be conducted in two phases. The first phase will be a 6-month pilot study with a follow-up at 8 months (after the summer holidays) to evaluate the feasibility: of retention, adherence, acceptability, and fidelity (Eldridge et al, 2010). The second will be a definitive study of 6 months with a follow-up at 8 and 12 months to evaluate the efficacy. The study will consist of three parallel, three-arm groups with a 1:1:1 allocation ratio.
To perform the protocol of the study, the SPIRIT 2013 guide was followed. The study was approved by the Research Ethics Committee of the University of Sonora Department of Nursing (EPD-007-2022).
Fifteen public schools (300 to 450 students) from Hermosillo, Sonora, Mexico will be conveniently invited to participate in the pilot study. The sample size was determined based on the capacity of providing the program and on finding possible positive effects on the variables of interest . The calculation of the sample size is not essential in a pilot study, where its main objective is to know the feasibility of the intervention and information regarding the response variables to later carry out the sample size calculation for a future definitive trial (Eldridge, 2016).
Once the informed consent and assent have been signed by the parents and children (respectively), the baseline measurements will be made over 4 weeks. The schools and participants that meet the inclusion/exclusion criteria will be randomly assigned to one of the three arms. 1). Planet Nutrition Program (PNP) implemented by nutrition and physical activity advanced students (studying the last semesters of the degree or who have completed subjects but do not have the degree), 2). PNP implemented by school teachers and 3). a control group. An independent person from the recruitment and the intervention will perform the random allocation of the schools. This will be stratified by socioeconomic level. The random number sequence will be generated using the software "Research Randomizer" https://randomizer.org/.
The baseline characteristics will be analyzed among groups, and an ANOVA analysis will be used for the quantitative variables, and a chi-square test for the categorical outcomes in order to assure that groups are similar in all variables. If there are significant differences among groups at baseline, an adjustment will be made in the analysis. To evaluate the differences between groups in the change of the BMI Z-score, body fat, and the other secondary variables at the beginning and at the end of the intervention, a mixed model will be used to consider the effect between groups and within groups. All analyzes will be performed by the intention to treat. If data is not obtained for any reason or subjects were excluded due to a protocol violation, they will be replaced by their baseline measurement. The R studio software will be used to perform the analysis.
