Importance: The prevalence of obesity among youths 2 to 19 years of age in the US from 2017 to 2018 was 19.3%; previous studies suggested that school lunch consumption was associated with increased obesity. The Healthy, Hunger-Free Kids Act of 2010 (HHFKA) strengthened nutritional standards of school-based meals.
Objective: To evaluate the association between the HHFKA and youth body mass index (BMI).
Design, setting, and participants: This cohort study was conducted using data from the Environmental Influences on Child Health Outcomes program, a nationwide consortium of child cohort studies, between January 2005 and March 2020. Cohorts in the US of youths aged 5 to 18 years with reported height and weight measurements were included.
Exposures: Full implementation of the HHFKA.
Main outcomes and measures: The main outcome was annual BMI z-score (BMIz) trends before (January 2005 to August 2016) and after (September 2016 to March 2020) implementation of the HHFKA, adjusted for self-reported race, ethnicity, maternal education, and cohort group. An interrupted time-series analysis design was used to fit generalized estimating equation regression models.
Results: A total of 14 121 school-aged youths (7237 [51.3%] male; mean [SD] age at first measurement, 8.8 [3.6] years) contributing 26 205 BMI measurements were included in the study. Overall, a significant decrease was observed in the annual BMIz in the period following implementation of the HHFKA compared with prior to implementation (-0.041; 95% CI, -0.066 to -0.016). In interaction models to evaluate subgroup associations, similar trends were observed among youths 12 to 18 years of age (-0.045; 95% CI, -0.071 to -0.018) and among youths living in households with a lower annual income (-0.038; 95% CI, -0.063 to -0.013).
Conclusions and relevance: In this cohort study, HHFKA implementation was associated with a significant decrease in BMIz among school-aged youths in the US. The findings suggest that school meal programs represent a key opportunity for interventions to combat the childhood obesity epidemic given the high rates of program participation and the proportion of total calories consumed through school-based meals.