Research Article
Implementing School-Based Policies to Prevent Obesity: Cluster Randomized Trial

https://doi.org/10.1016/j.amepre.2018.08.026Get rights and content

Introduction

Healthier school environments can benefit students, and school wellness policies may result in meaningful enhancements. Schools participating in federal child nutrition programs must implement wellness policies as mandated by law. The primary study objective is to assess effectiveness of implementing school-based nutrition and physical activity policies on student BMI trajectories.

Study design

Cluster randomized trial using 2 × 2 factorial design.

Setting/participants

Twelve randomly selected schools in an urban district. Students were followed for 3 years through middle school, fifth to eighth grades (2011–2015, n=595 students, 92.3% participation, 85.2% retention).

Intervention

Specific to randomized condition, support was provided for implementation of nutrition policies (e.g., alternatives to food-based rewards/celebrations) and physical activity policies (e.g., opportunities for physical activity during/after school).

Main outcome measures

Sex-/age-adjusted BMI percentile and BMI z-score; behavioral indicators. Data collected via standardized protocols.

Results

Analyses followed intention-to-treat principles, with planned secondary analyses (conducted 2016–2018). Students at schools randomized to receive support for nutrition policy implementation had healthier BMI trajectories over time (F=3.20, p=0.02), with a greater magnitude over time and cumulatively significant effects 3 years post-intervention (β=–2.40, p=0.04). Overall, students at schools randomized to receive the nutrition intervention had an increase in BMI percentile of <1%, compared with students in other conditions, whereas BMI percentile increased 3%–4%. There was no difference in student BMI between those in schools with and without physical activity policy implementation. Examining behavioral correlates in eighth grade, students at schools randomized to the nutrition condition consumed fewer unhealthy foods and sugar-sweetened beverages, and ate less frequently at fast-food restaurants (all p<0.03).

Conclusions

This cluster randomized trial demonstrated effectiveness of providing support for implementation of school-based nutrition policies, but not physical activity policies, to limit BMI increases among middle school students. Results can guide future school interventions.

Trial registration

This study is registered at www.clinicaltrials.gov NCT02043626.

Section snippets

INTRODUCTION

Schools have figured prominently in national discourse about policy approaches to prevent childhood obesity because they afford concentrated contact, teach health education, provide meals, and can model health-promoting environments.1, 2, 3 In 2004, all school districts participating in the U.S.’s federal meal programs were required to create a committee of stakeholders and write a school wellness policy.4 School wellness policies required schools to set goals for physical education and

METHODS

This study was conducted in New Haven, Connecticut, an urban district with >21,000 students. Using a quantitative coding system to evaluate written school wellness policies in all Connecticut districts, New Haven's policy scored higher than any other district.18, 19 Therefore, it was an ideal setting to assess implementation of a strongly written school wellness policy.

Twelve schools (kindergarten through eighth grade [K–8]) were randomly selected from among the 50 K–8 district schools. All

RESULTS

Mean age of students at study entry was 10.9 years (SD=0.6). Racial/ethnic categorization generally reflected distribution of students in the district: 47.2% Hispanic, 35.0% black, and 17.8% white/other. Students in study conditions did not differ by age or race. Girls accounted for 54% of participants. The physical activity–only condition had significantly more girls; the largest study school, randomized to this condition, was a school where two thirds of students were female. Mean age- and

DISCUSSION

Students who attended schools that were randomized to receive support to implement nutrition-focused school wellness policies were significantly less likely to experience an increase in BMI across middle school (from fifth through eighth grades) than students in comparison schools. At the end of the study, these students reported lower consumption of unhealthy foods and sugar-sweetened beverages, although there was no effect on consumption of healthy foods and beverages. The magnitude of

CONCLUSIONS

Implementation of school-based nutrition policies should be an important component of multisector interventions to prevent an adverse trajectory of weight gain. This trial—focused on school wellness policy support and implementation—had a larger effect than previous studies, indicating that school-based structural interventions may be particularly promising. School systems should consider earlier interventions; in this study, more than one half of students were already overweight or obese by

ACKNOWLEDGMENTS

This study was funded by the National Institute of Child Health and Human Development, NIH (1R01 HD070740, JR Ickovics and MB Schwartz, Multiple PIs), with additional support from the U.S. Centers for Disease Control and Prevention and Yale-Griffin Prevention Research Center (5U48DP000053, JR Ickovics, PI). The funders had no role in the design, implementation, evaluation, or interpretation of this study. More information on the protocol is available at ClinicalTrials.gov NCT02043626.

No

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