Obese Peers' Influence on Students' BMI: Heterogeneity in Race and Sex

Objectives: In this study, we investigate peer influence on obesity, with a focus on race and sex. Methods: We conducted econometric analysis of longitudinal health data of 277,566 public school students, ages 5-13 years. Results: A percentage point increase in the proportion of obese students within the same grade increased a student's BMI z-scores by about 4 one-thousandths of a standard deviation. On racial peers, the standard deviation increase in BMI z-score is 3.9 one-thousandths for Hispanics or Caucasians and 4.9 one-thousandths for African Americans. Influence of obese peers is nearly identical for boys and girls. Conclusions: Such a small magnitude of obese peers' estimate suggests that classroom peers do not play a substantial role in weight gain or loss in elementary schools.