Methods:

This was a quasi-experimental study design conducted within public schools across the country. Student data were obtained from the Early Childhood Longitudinal Study, a nationally representative sample. This analysis included data collected in 2007, when students were in eighth grade. Students were categorized by type of school lunch they usually obtained (free/reduced price, regular price, or none). Among the 7,050 public school students who participated in 2007, students were excluded if their principal reported that no students participated in lunch programs, they resided in a state with fewer than five observations, or they were missing data on school lunch programs, height or weight, lunch participation, or other covariates, leaving 4,870 students from 40 states. Missing data were equally common in states with different school meal laws, but more common among boys, racial/ethnic minorities, and students who resided in urban areas, were of low socioeconomic status (SES), or were obese. The intervention examined was state laws governing school meal nutrition standards. States with standards that exceeded US Department of Agriculture (USDA) school meal standards were compared with states that did not exceed USDA standards. The parameter of interest was the interaction between state laws and student lunch participant status, i.e., whether disparities in weight status between school lunch participants and nonparticipants were smaller in states with stricter standards. The primary outcome of interest was body mass index percentile and obesity status for the students.