Association between school food environment and practices and body mass index of US public school children.

BACKGROUND: With the ongoing interest in implementing school policies to address the problem of childhood obesity, there is a need for information about the relationships between school food environments and practices and children's weight status.

OBJECTIVE: To examine the association between school food environments and practices and children's body mass index (BMI; calculated as kg/m(2)).

DESIGN: The study used data from the third School Nutrition Dietary Assessment Study, a cross-sectional study that included a national sample of public school districts, schools, and children in the 2004-2005 school year. Data on school food environments and practices were collected through on-site observations and interviews with school principals, and children were weighed and measured by trained data collectors.

SUBJECTS/SETTING: The study included 287 schools and 2,228 children in grades 1 through 12.

STATISTICAL ANALYSES PERFORMED: Ordinary least squares regression was used to estimate the associations between school food environments and practices and BMI z scores and logistic regression was used to estimate associations between school food environments and practices and the likelihood of obesity (defined as BMI-for-age >or=95th percentile). Models included controls for sociodemographic characteristics of schools and children, to control for potential endogeneity of school environments and practices, as well as controls for children's dietary and physical activity behaviors outside of school.

RESULTS: Among elementary school children, offering french fries and similar potato products in subsidized school meals more than once per week and offering dessert more than once per week were each associated with a significantly higher likelihood of obesity. Among middle school children, the availability of low-nutrient, energy-dense foods in vending machines in or near the foodservice area was associated with a higher BMI z score, and the availability of such foods for à la carte purchase in the cafeteria was associated with a lower BMI z score.

CONCLUSIONS: Findings from this analysis suggest that limiting children's access to low-nutrient, energy-dense foods at school may hold promise as a tactic for reducing children's total calorie intake and controlling children's BMI.