Efficacy of a School-based Obesity Prevention Program in Mexican Schoolchildren: Cluster Randomized Controlled Trial

There is evidence that obesity prevention programs show positive effects on obesity and lifestyle parameters. However, the effect of the programs delivered by different implementers is unknown, and in Mexico, the available studies present methodological limitations. The aim of this study is to evaluate the feasibility and efficacy of a school-based obesity prevention program implemented by nutrition and physical activity advanced students compared to a control group and implemented by school teachers compared to a control group of Mexican schoolchildren. This is a cluster randomized controlled trial. Schoolchildren from different public schools in Hermosillo , Sonora will be invited to participate. The schools will be randomly assigned to one option:1) the Planet Nutrition Program (PPN) delivered by advanced students, 2) PPN by school teachers, or 3) a control group. A 6-month pilot study with a follow-up at 8 months (after the summer holidays), followed by a definitive study with a follow-up at 8 and 12 months will be conducted.The intervention will consist of nutrition education sessions, physical activity, and the provision of nutrition information for parents. The BMI Z-score, body fat, other obesity, and lifestyle parameters will be evaluated at baseline and at the end of the study. A mixed effects model will be used to evaluate the differences between the groups. The investigators expect that the program could be a model of obesity prevention with a high potential for dissemination in Mexican schools.

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.

Eligibility Criteria:
Inclusion Criteria:

* Schools:

  * school directors and teachers wish to participate.
  * availability of space for physical activity classes.
  * the school has at least 20 children per 4th-grade group.
* Schoolchildren:

  -be a 4th grade student (9 to 11 years old).
* Implemeters:

  * receive 80% of the program training.
  * respond satisfactorily to a questionnaire that tests knowledge of the program

Exclusion Criteria:

* Schools: participating in another similar study.
* Schoolchildren: Having a personal condition that prevents physical activity or a condition that parents consider should not involve the child.