Food Environments Within and Outside of Schools Play a Critical Role in Curtailing the Rise in Obesity among School-Aged Children over Time

Abstract

Background: Sound evidence for effective community-based strategies is needed to curtail upward trends in childhood obesity in the United States (US).

Objectives: The aim of the study was to assess the association between school and community food environments and the prevalence of obesity over time.

Methods: Data were collected from K-12 schools in 4 low-income New Jersey cities in the US. School-level obesity prevalence, calculated from nurse-measured heights and weights at 4 time points, was used as the outcome variable. Data on the school food environment (SFE) measured the healthfulness of school lunch and competitive food offerings annually. The community food environment (CFE), i.e., the number of different types of food outlets within 400 m of schools, was also captured annually. The count and presence of food outlets likely to be frequented by students were calculated. Exposure to composite environment profiles both within schools and in communities around schools was assessed using latent class analysis. Data from 106 schools were analyzed using multilevel linear regression.

Results: The prevalence of obesity increased from 25% to 29% over the course of the study. Obesity rates were higher in schools that had nearby access to a greater number of limited-service restaurants and lower in schools with access to small grocery stores and upgraded convenience stores participating in initiatives to improve healthful offerings. Interaction analysis showed that schools that offered unhealthier, competitive foods experienced a faster increase in obesity rates over time. Examining composite food environment exposures, schools with unhealthy SFEs and high-density CFEs experienced a steeper time trend (β = 0.018, P < 0.001) in obesity prevalence compared to schools exposed to healthy SFE and low-density CFEs.

Conclusions: Food environments within and outside of schools are associated with differential obesity trajectories over time and can play an important role in curtailing the rising trends in childhood obesity.

Keywords: childhood obesity; community food environment; longitudinal analysis; obesity trajectory; obesity trends; school food environment; school food policy; school food programs.

FIGURE 1

Predicted probability of obesity for schools based on their food environment type.¹ Notes: The estimated slopes and P values for the 4 groups are the following: Group 1: β = 0.004, P = 0.297; group 2: β = 0.005, P = 0.254; group 3: β = –0.007, P = 0.436; group 4: β = 0.018, P < 0.001. The full label for category 4 is as follows: Unhealthy SFE; high-density CFE with fewer upgraded stores. CFE, community food environment; SFE, school food environment. ¹The environment type categories were determined through latent class analysis. The predicted obesity prevalence was calculated from the regression model reported in TABLE 4 for the 4 environment types while fixing all other predictors at their mean.

FIGURE 2

Predicted probability of obesity for schools with composite healthier food environment and composite unhealthier food environment profiles.^{1 1}The characteristics of the composite healthier and unhealthier environment profiles are described in Appendix C. ∗Indicates that there is a significant difference (P < 0.05) between the estimated obesity rate associated with the healthier food environment and the estimated obesity rate associated with the unhealthier food environment. These comparisons were based on z-tests for differences in proportion, obtained from the lincom command analyzed after the margins command in Stata 17.