Loss of Access to Universal Free School Meals and Body Mass Index in Students.

Importance: Deimplementation of nationwide universal free school meals (UFSM) after the COVID-19 pandemic has been associated with worsening participation in school meal programs and childhood food insecurity; however, the health impacts are unknown. Objective: To assess the association between loss of UFSM and the body mass index z score (BMIZ) among youths. Design, Setting, and Participants: This was a longitudinal cohort study of children and adolescents from low- and low-middle-income households in 29 US states in school years 2021-2022 through 2023-2024. Participants were matched to their residentially assigned school, and the study was limited to schools that were ineligible for other federal UFSM programs based on the percentage of students directly certified to receive free or reduced-price lunch (ie, low-poverty schools). Participants were youths aged 5 to 18 years who received health care at community health care organizations and had biologically plausible height and weight measurements and at least 1 BMI measurement in both the prepolicy year and 1 of the postpolicy years. Exposure: Loss of UFSM after June 2022. Main Outcome and Measures: BMIZ, based on the Centers for Disease Control and Prevention's 2022 extended BMIZ reference charts. Changes in BMIZ were compared between youths who lost UFSM (exposure group) and those who retained UFSM access because they lived in a state adopting statewide UFSM policies (comparison group), using propensity score-weighted difference-in-difference (DID) models for the overall sample and stratified by income. Results: The cohort (N = 42 385) had mean (SE) age of 12.28 (0.03) years and mean (SE) BMIZ of 0.86 (0.01); 51.9% were female. Most students were publicly insured (80.2% [SE, 0.40%]) and from households below 185% of the federal poverty level (80.3% [SE, 0.36%]). BMIZ and demographic characteristics were well matched between the exposed and unexposed groups. Among youths living in states that retained UFSM, mean within-person BMIZ declined from baseline to postpolicy year 2 (change, -0.08; 95% CI, -0.10 to -0.06; P < .001). Youths living in states that lost (vs retained) UFSM had a significantly smaller BMIZ decrease (DID for postpolicy year 2 overall: 0.03 [95% CI, 0.01-0.06]; P = .007). Conclusions and Relevance: In this cohort study of youths from low- and low-middle-income households, the loss of UFSM was associated with unfavorable BMIZ trajectories. The findings suggest expanding UFSM eligibility in schools may have potential to improve BMI for this population.