National School Lunch Program Participation and Weight Trajectories Among Low-Income Children

Year: 2009

Research Center: Department of Nutrition at the University of California, Davis

Investigator: Hernandez, Daphne, Lori A. Francis, and Emily Doyle

Institution: Pennsylvania State University

Project Contact:
Daphne Hernandez
Pennsylvania State University
S110 Henderson Building
University Park, PA 16802
Phone: 814-867-2245


The National School Lunch Program (NSLP), established in 1946, served more than 30.5 million children each day in 2007. The NSLP is the second most expensive Federal food program, trailing only the Food Stamp Program (now the Supplemental Nutrition Assistance Program), at a cost of $8.7 billion per year. The NSLP is an intervention and prevention program intended to mitigate poor nutrition and promote healthy development during school hours by providing a nutritional safety net for low-income children. The program increases the availability of food and protein and is associated with lower intakes of added sugars and increased intakes of vitamins and minerals. Although the NSLP was not originally designed as an obesity-prevention program, it has undergone criticism for contributing to an increase in dietary fat and calories among children who participate in the program.

Given the pervasiveness of the NSLP and the adverse health and economic consequences related to being overweight, this study applies longitudinal data to investigate indepth the association between participation in NSLP by income-eligible children and their weight status from kindergarten to eighth grade. Specifically, the study uses data from kindergarten to eighth grade to examine (1) the various participation patterns (that is, persistent, transient, and no participation) in the NSLP, (2) how participation relates to childhood body mass index (BMI) trajectories, and (3) whether participation influences girls’ BMI trajectories differently than boys’ trajectories.

The study contributes to the literature in several ways. First, the study provides a longitudinal examination of the patterns of NSLP participation. This information is necessary to gain a greater understanding of whether socioeconomic characteristics differ between children who consistently or temporarily participate in the program and possible impacts on weight gain. Second, the study examines the manner in which program participation influences BMI trajectories from kindergarten to eighth grade. Most studies that have investigated the NSLP and weight trajectories have focused on cross-sectional data or longitudinal data from elementary school years. Third, the focus on gender differences is important as studies have shown a positive association between food assistance program participation and weight status for girls.

Data were drawn from the Early Childhood Longitudinal Study (ECLS-K), a nationally representative, longitudinal study of children’s school experiences and development collected by the National Center for Education Statistics (NCES). The ECLS-K follows children in the fall and spring of kindergarten (1998-1999), the fall and spring of first grade (1999-2000), the spring of third grade (2002), fifth grade (2004), and eighth grade (2007). For consistency, the study focused on data collected in the spring term of each grade listed.

Children’s BMIs were calculated from direct measurement of height and weight collected at each time point. Parental reports were used to determine participation in the NSLP (that is, received free or reduced-price lunches) at each data-collection survey. Three mutually exclusive variables that capture the duration of participation in the NSLP were created. Families who never participated in the NSLP at any of the five time points comprised the no-participation group. Families who participated in the NSLP at all five time points comprised the persistent participation group. Families who participated at some grade levels but not in others comprised the transient participation group. Factors capturing child, maternal, household, community, and State-level characteristics that are related to program participation and weight status were included in the models as controls. Logistic regression models estimated the likelihood of children experiencing persistent and transient participation, while mixed models estimated the effects of NSLP participation on BMI from kindergarten to eighth grade.

Logistic regression results indicate that similar disadvantaged socioeconomic characteristics are associated with persistently or temporarily participating in the NSLP. Thus, families with comparable background characteristics are opting into the program, although their patterns of participation differ. Results from mixed models suggest that children enter kindergarten at a healthy weight, indifferent of program participation. However, NSLP participation among income-eligible girls influences more rapid weight gain over time. Income-eligible girls displayed higher BMI averages beginning in third grade compared with income-eligible nonparticipating girls. Differences were not observed among income-eligible boys. The association between NSLP participation and weight status may not only be related to the food available during the lunch hour but also to the environment in which the children reside and the biological differences between girls and boys.

Direct inquiries about this study to the Project Contact listed above.