Self-reported height and weight may lead to inaccurate estimates of associations between BMI and health indicators. The purpose of this study is to assess anthropometric misreporting in emerging adults, compare weight classification by self-reported and direct measures, and examine associations of self-reported and direct measures with cardiometabolic biomarkers.

Self-reported and directly measured height and weight were obtained in five waves of a nationally representative cohort study of U.S. tenth graders (n=2,785) conducted in 2010–2016; data were analyzed in 2018. Cardiometabolic biomarkers were assessed in three waves in a systematically recruited subsample (n=567). Pearson correlations (r) and Lin's concordance correlations (ρ_c) evaluated misreporting. Gwet agreement coefficient-1 evaluated weight classification agreement by self-reported and direct measures. Generalized estimating equations examined associations of cardiometabolic biomarkers with self-reported and direct measures.

Participants overreported height by 1.0–1.7 cm and underestimated weight by 0.6–1.7 kg. Self-reported BMI was 0.6–1.0 lower than measured. Self-reported and measured height, weight, and BMI were strongly correlated (r=0.88–0.97, 0.86–0.98, and 0.65–0.96, respectively) and concordant (ρ_c=0.82–0.96, 0.94–0.97, and 0.65–0.95, respectively). Agreement of weight classification by self-reported and direct measures ranged from Gwet agreement coefficient-1=0.79–0.94. Associations of ten cardiometabolic biomarkers with self-reported BMI, measured BMI, and waist circumference were similar in magnitude, direction, and precision.

Self-reported and measured BMI were strongly correlated and concordant, providing substantial to near-perfect agreement in weight classification. Findings suggest self-reported BMI in U.S. emerging adults provides nearly identical estimates of associations with cardiometabolic biomarkers.