Rates of overweight and obesity have increased dramatically during the past 2 decades. Children obtain a large fraction of their food energy while at school.

To estimate the relationship between participation in school meal programs and children's body mass index (BMI) and their likelihood of being overweight or obese, testing the hypothesis that school meal participation influences students' weight status, as measured by their BMI and indicators of overweight and obesity.

A cross-sectional design in which a regression model was used to estimate the association between participation in the School Breakfast Program and National School Lunch Program and children's BMI and risk of overweight or obesity, controlling for a wide range of student and school characteristics.

Participants included a nationally representative sample from the third School Nutrition Dietary Assessment Study of 2,228 students in grades 1 through 12 for whom height and weight measurements were obtained. These students, along with their parents, each completed a survey.

Multivariate regression models were used to examine the relationship between usual school meal participation and BMI and indicators of whether students were overweight or obese. These models controlled for students' demographic and socioeconomic characteristics, levels of physical activity, usual eating habits, screen time, and school characteristics.

No evidence was found of any relationship between usual school lunch participation and any of four different measures of weight status based on students' BMI. School breakfast participation was associated with significantly lower BMI, particularly among non-Hispanic, white students.

There was no evidence that either the school breakfast or lunch program is contributing to rising rates of childhood obesity. In fact, School Breakfast Program participation may be a protective factor, by encouraging students to consume breakfast more regularly.