California and federal school nutrition policies and obesity among children of Pacific Islander, American Indian/Alaska Native, and Filipino origins: Interrupted time series analysis

Background
Obesity prevalence remains high among children of Pacific Islander (PI) origin, Filipino (FI), and American Indian/Alaska Native (AIAN) origins in the United States. While school nutrition policies may help prevent and reduce childhood obesity, their influences specifically among PI, FI, and AIAN children remain understudied. We evaluated the association of the California (CA) state school nutrition policies for competitive food and beverages and the federal policy for school meals (Healthy, Hunger-Free Kids Act of 2010 (HHFKA 2010)) with overweight/obesity among PI, FI, and AIAN students.

Methods and findings
We used an interrupted time series (ITS) design with FitnessGram data from 2002 to 2016 for PI (78,841), FI (328,667), AIAN (97,129), and White (3,309,982) students in fifth and seventh grades who attended CA public schools. Multilevel logistic regression models estimated the associations of the CA school nutrition policies (in effect beginning in academic year 2004 to 2005) and HHFKA 2010 (from academic year 2012 to 2013) with overweight/obesity prevalence (above the 85 percentile of the age- and sex-specific body mass index (BMI) distribution). The models were constructed separately for each grade and sex combination and adjusted for school district-, school-, and student-level characteristics such as percentage of students eligible for free and reduced price meals, neighborhood income and education levels, and age. Across the study period, the crude prevalence of overweight/obesity was higher among PI (39.5% to 52.5%), FI (32.9% to 36.7%), and AIAN (37.7% to 45.6%) children, compared to White (26.8% to 30.2%) students. The results generally showed favorable association of the CA nutrition policies with overweight/obesity prevalence trends, although the magnitudes of associations and strengths of evidence varied among racial/ethnic subgroups. Before the CA policies went into effect (2002 to 2004), overweight/obesity prevalence increased for White, PI, and AIAN students in both grades and sex groups as well as FI girls in seventh grade. After the CA policies took place (2005 to 2012), the overweight/obesity rates decreased for almost all subgroups who experienced increasing trends before the policies, with the largest decrease seen among PI girls in fifth grade (before: log odds ratio = 0.149 (95% CI 0.108 to 0.189; p < 0.001); after: 0.010 (−0.005 to 0.025; 0.178)). When both the CA nutrition policies and HHFKA 2010 were in effect (2013 to 2016), declines in the overweight/obesity prevalence were seen among White girls and FI boys in fifth grade. Despite the evidence of the favorable association of the school nutrition policies with overweight/obesity prevalence trends, disparities between PI and AIAN students and their White peers remained large after the policies took place. As these policies went into effect for all public schools in CA, without a clear comparison group, we cannot conclude that the changes in prevalence trends were solely attributable to these policies.

Conclusions
The current study found evidence of favorable associations of the state and federal school nutrition policies with overweight/obesity prevalence trends. However, the prevalence of overweight/obesity continued to be high among PI and AIAN students and FI boys. There remain wide racial/ethnic disparities between these racial/ethnic minority subgroups and their White peers. Additional strategies are needed to reduce childhood obesity and related disparities among these understudied racial/ethnic populations.