Locally implemented prevention programs may reverse weight trajectories in half of children with overweight/obesity amid low child-staff ratios: results from a quasi-experimental study in France

The rates of obesity and overweight are still increasing worldwide [1], and remain unchanged in France, affecting nearly 1 in 5 children, with the highest prevalence in deprived populations [2]. Obesity in childhood is difficult to reverse [3] and often persists into adulthood, causing many health problems [4]. According to systematic reviews, school-based prevention programs may be effective in promoting healthy behaviors [5‐7]. These programs typically include educational, environmental, and social activities designed to improve dietary habits and reduce sedentary time in schoolchildren [8, 9]. However, even sound, evidenced–based interventions yield modest effects on adiposity measures [10, 11].

Insights from implementation science may partly explain these mitigated outcomes. How authorities bring prevention programs into the school communities may dramatically influence local dynamics. In France, the Education, Health, and Territory (EST) program included the core principles of health-promoting schools, such as staff training and support to develop school health policies focusing on the school environment and adaptation to a local context, community involvement, and the development of health-related knowledge, skills, and competencies [12], but decisions and approvals came from higher authorities, and this “top-down” approach created a reluctance to participate locally [13]. In addition, health education programs require teachers to acquire additional competencies [14] and to include health education in their curriculum [15]. However, teachers’ work is already described as increasing in complexity and intensity because of societal changes, reformed and increased work tasks, and multitasking [16]. Urgent unforeseen priorities, competing responsibilities, and high workload may also constitute barriers to successful implementation [17], especially when training and activities seem complex or theoretical [13].

The success of school-based prevention initiatives involves balancing evidence-based interventions with the flexibility to permit local educational communities to target their specific needs [18]. Fostering commitment entails giving local implementers the freedom to select the intervention components that best meet their needs and providing training to persons interacting with children [19], including teachers and ancillary staff in charge of non-teaching duties at school [13], such as catering and extracurricular activities. Following these core principles, some associations provide organizational backbone support [20] to local communities in charge of the education and care of children. This alternative approach to downstream interventions may induce variation between locally implemented programs, warranting a thorough examination of the relationship between process and outcome indicators through a quasi-experimental study design [21].

The aims of the present study were to assess changes in weight status among schoolchildren between the first and last year of primary education in response to locally implemented school-based prevention programs, and to assess the influence of process indicators, expressed as child-staff ratios (CSRs) by occupation/component, on these changes.

Of the 900 first-grade children schooled in the four participating municipalities, 23 (2.7%) were not enrolled based on parental request, whereas 50 (5.6%) were lost to follow-up and excluded from further analyses. Comparisons revealed that those schooled in deprived areas were less frequently lost to follow-up (3.9%) than others (8.9%; p = 0.007). The 827 children included in the analyses (Table 2) were gender-balanced, with an average age of 6.4 years (SD 0.79), and 59.3% were schooled in deprived areas during the first year of primary education. The mean age was significantly higher in City 1 than the other municipalities (p < 0.001), whereas children schooled in deprived areas were significantly overrepresented in City 4 (77.4%) and City 1 (71.6%) compared to City 3 (45.3%) and City 2 (0%; p < 0.001). The distributions of gender and weight status were similar between municipalities.

At inclusion, 137 children met the criteria for overweight (16.6%) and 32 for obesity (3.9%; Table 3). Four years later, 101 children met the criteria for overweight (12.2%) and 31 for obesity (3.7%; p = 0.002). In children who remained overweight (n = 58), the BMI z-score decreased from 2.24 (0.48) to 2.04 (0.69; p = 0.014), but it remained unchanged in children with obesity [4.51 (1.82) vs. 4.09 (1.49)]. Weight status improved in half of the children with overweight/obesity (48.2 and 59.4%, respectively), with lower estimates in City 1 (38%) and City 2 (45.5%) and higher estimates in City 3 (68.4%) and City 4 (55.1%). Concomitantly, weight status worsened in 6.6% of children with overweight/normal weight.

The local implementers involved in training sessions were mainly municipal staff in charge of serving midday school meals, which is compulsory in France, and those in charge of designing and facilitating creative, interactive activities at school between and after classes. Over the 4-year study period, City 1 requested two training sessions on HE for the school catering staff, whereas City 2, City 3, and City 4 requested 3, 5, and 15 training sessions, respectively, on HE and PA for staff in charge of the school catering and staff in charge of ECAs. Finally, each participating municipality implemented a specific variation of the VIF program over the 4-year period (Table 4).

In the univariate analysis (Table 5), estimated positive 4-year weight changes increased significantly with low CSRs compared to moderate CSRs, even after adjusting for sex, age, and deprived school area. When the four variations of the VIF program were entered as categorical covariates in the regression model (Table 6), the estimated positive 4-year weight change was significantly higher in low-to-moderate CSR multicomponent interventions than the reference (moderate CSR single-component intervention), and increased with age after adjustment. The moderate CSR multicomponent intervention had a similar effect as the reference program. In children with overweight/normal weight at inclusion (N = 795), the estimated 4-year negative weight change decreased with age and was unrelated to the process indicators being studied.

Between the first and the last year of primary education, weight status improved in half of the schoolchildren characterized as overweight/obesity at inclusion. In children who remained overweight, the BMI z-score diminished significantly over time, and being schooled in a deprived area had a negative, but not significant, influence.

The implementation mode under study was similar to traditional school-based prevention programs in that it provided training and materials to local stakeholders [12]. However, the VIF program provides tools previously tested in real-life settings and addresses thematic content over a long period of time based on a comprehensive social marketing methodology [30]. In addition, the interventions avoided interference with teachers’ curricula, enriching the existing school environments/interactions rather than implementing unusual and potentially disruptive procedures [13], and promoting experiential learning instead of lectures [19]. On the other hand, upstream discussions revealed that teachers had no particular interest in adding HE/PA to their curriculum, despite the recommendations of health experts [31]. Imposing their participation may have jeopardized local dynamics [13].

Yet, the data analyses elicited interesting insights. First, weight trajectories were reversed in half of children with overweight/obesity over 4 years, compared to approximately 38% over a 9-year period at the national level [2, 32]. Negative weight changes were marginal, and overweight severity diminished over time. This is important because 16.6% of children were considered overweight and 3.9% obese in the participating municipalities, compared to 10.1 and 2.4% of French children aged 6–10 years [2]. The higher than national average estimates could be due to the high level of social deprivation in these locations [33, 34], except for City 2, where others factors could be at play [35]. Second, positive changes in weight status were steadily related to lower CSRs, even after adjusting for sex, age, and deprived school area. Multi-component programs are widely acknowledged to be more successful than single-component interventions [36]. However, moderate CSRs weakened this benefit of the intervention in City 2, and the presence of low CSRs characterized the most effective variations in the VIF program. Many studies have investigated the relationship between CSRs and outcomes in childhood education and care, mostly on the cognitive and emotional development of the child, but the first attempt to systematically review and meta-analyze this highly complex and heterogeneous literature revealed few, if any, relationships [21]. These process indicators are often overlooked in obesity prevention program evaluations [10], and the reasons for variation at the local level warrant further examination. However, CSRs seem pivotal in childhood obesity prevention programs, though their optimal values still remain to be determined. Finally, it seems that older age had a positive influence on 4-year weight changes, though the children were relatively close to one another in regards to age (mean 6.38 years, SD 0.76). Minor differences in this life period could mark the transition between two milestones of cognitive development, but the complexity of developmental theories warrants caution [37]. If confirmed elsewhere, this result would advocate, at the very least, for including 2nd grade children in these programs.

The present study has limitations related, in part, to the implementation mode under examination. The avoidance of prescriptive approaches may have contributed to fostering local dynamics, but also precluded comparisons between balanced interventions. The lack of a control group constitutes a major limitation, as many factors besides the intervention could have influenced findings during the 4-year period. However, quasi experimental designs are frequently used to examine the effects of social programs [38], and assessing the intervention effect between the first and last year of primary education is consistent with monitoring school-based prevention programs. Furthermore, interactions between parents, children, and municipal school staff in charge of PA and HE were targeted by the programs but not directly assessed in the study. In addition, the municipalities participating in the study may have differed from other cities in France, as they systemically monitor the weight status of schoolchildren under their supervision. Considering the present findings, low CSRs in childhood prevention programs could be even more important in deprived areas [39]. This proportionate universalism [40] warrants further examination in relation to parental involvement and other variables of interest [35]. Nevertheless, a strength of this prospective study is that it relied on comparisons of reliable estimates of weight status collected twice at a 4-year interval among the same children at primary schools from distant municipalities, which avoided contamination.

Our findings suggest that training ancillary school staff in experiential-focused interventions in locally implemented school programs contributed positively to reducing childhood obesity during the four years of primary education without interfering in educational activities. They also provide preliminary evidence that low CSRs could be pivotal for optimal outcomes, especially in deprived areas, which warrants further investigation using a controlled study design.