The Vivons en Forme (VIF; “live healthy”) organization is a continuation of the obesity prevention scheme previously known as Epode,(19) a community-based prevention program aimed at promoting healthier lifestyles among children and their families, and involving municipal services in charge of child education and care under the supervision of a local coordinator. However, compared to Epode, the non-governmental organization acting as a backbone structure changed its process in 2010, following four new pathways in order to improve program efficiency. First, the name of the program was changed in order to be better accepted by the local stakeholders, including families and children, removing the mention of obesity in the name of the interventions Second, a full social marketing approach was included for each yearly implemented thematic.(20) Third, toolkit materials were pilot-tested in living labs to collect input from users and stakeholders before application in real-life settings, and in the participating cities.(21) Lastly, the implementation process was centered around local stakeholders, including but not limited to school staff, as well as participation and empowerment.(22) The principle aim was to foster self-efficacy and a long-lasting effect in local school staff newly involved in the field of prevention and health promotion. Local stakeholders have the freedom to shape their programs, and can request additional interventions during the course of the program. The basic underlying principle of this “choose-and-pick” approach was to foster staff involvement and sustainably change their interactions with children and parents. Each participating municipality applies for a minimal 5-year period, and their representatives have to regularly attend regional coordination meetings to receive up-to-date information on training sessions and tool upgrades.
Study design and participant selection
To meet the study objectives, a prospective design was used. Only the four municipalities that systematically monitored schoolchildren’s weight status were invited to participate. In these municipalities, VIF counselors (an engineer in nutrition and public health, a sociologist, and the leading coordinator of the program organized training sessions for the municipal staff in charge of canteen service and extracurricular activities (ECAs) in primary schools. Training sessions and toolkits integrated roadmaps for conducting interactive activities with the children and reinforce child-staff interactions via concrete experiences (Table 1). Brochures highlighting the beneficial effect of HE and PA for children were systematically provided to parents.(22) They included tips on how to help kids stay hydrated by drinking water, on breakfast preparation, food breaks (including fruits), avoiding snacking between meals, on treats and smart portion sizes, and how to easily cook healthy meals at low cost.
School nurses used a body mass index (BMI) chart established by the International Obesity Task Force, which allows classification of children into weight categories(23) (i.e., underweight, normal weight, overweight, and obesity), to assess the weight status of first-grade children at the school premises several weeks before the launch of each program in 2011. Children wore light clothes and no shoes during the weighing sessions. In addition, BMI Z-scores were computed using BMI-for-age reference standards(24) in order to account for overweight/obesity severity. Baseline and follow-up weight status, with BMI z-scores, were matched for gender and age at inclusion, and whether children were schooled in a zone of priority education (zone d’education prioritaire, ZEP) was indicated. ZEP refers to schools in deprived, usually urban, settings that are earmarked for special state support. The decision to categorize a school as a ZEP lies with the administrative authorities, who can release additional funding to finance special needs education. A follow-up weight assessment using the same methodology was performed among the same children in 2015. When it comes to the process evaluation, the number and occupation (canteen service or ECAs) of persons who attended training sessions between 2011 and 2015 were systematically recorded by thematic component (HE and/or PA).
Data blinding and confidentiality
A study number was attributed to each municipality (City#) and each child in the database to ensure confidentiality. The final database was completed in 2016, but anonymized data were transmitted to researchers in charge of statistical analyses in 2018 due to the administrative authorization procedure in each participating city.
Process indicators were expressed as numberand occupation of school staff attending training sessions by thematic component in each municipality, and then converted into child-staff ratios (CSRs), the number of children for each trained staff member, by occupation and thematic session. Because an average ratio of 8 children per adult was found in early childhood education and care settings,(25) the CSR was classified as “low” if between 1 to 5 children per adult, “moderate” if 6–9 children per adult, and “high” if > 10 children per adult. Categorical data were expressed as numbers and percentages and compared using the chi-squared test. Numerical data were expressed as means and standard deviations (SDs) and compared by one-way analysis of variance or the non-parametric Wilcoxon comparison test. Outcome indicators were 4-year changes in weight status, which were considered “positive” if obesity changed to over/normal weight or if overweight changed to normal-weight, and “negative” if normal weight changed to overweight/obesity or if overweight changed to obesity. To investigate the influence of process indicators on weight changes, we entered the CSRs (low, moderate, high) by occupation (canteen service/ECA) and thematic component (HE/PA) as interaction terms in a logistic regression using positive 4-year weight change as the binary outcome (yes/no), with adjustments for age at inclusion, gender, and school area (deprived/non-deprived). The same statistical procedure was employed with negative 4-year weight change as a binary outcome in children characterized as over/normal weight at inclusion. Estimates were expressed as odd ratios (ORs) with 95% confidence intervals (CIs). Statistical analyses were performed using the SPSS statistical package, version 20 (SPSS, Chicago, Illinois, United States).