Background <p>Obesity and metabolic syndrome (MS) accelerate arterial stiffening, increasing cardiovascular (CV) risk after transplant. BMI is limited by inability to differentiate muscle, fat mass, and fat distribution patterns. The aim of this study was to identify the best anthropometric measure to detect arterial stiffness as assessed by pulse wave velocity (PWV) in a racially diverse pediatric transplant population.</p> Methods <p>Kidney transplant recipients 6–20&#xa0;years old and ≥ 6&#xa0;months post-transplant were prospectively enrolled. PWV was measured oscillometrically by Mobil-O-Graph. Skeletal muscle-to-fat mass ratio (SM:FM) and percent body fat (PBF) were evaluated by dual-frequency bioelectrical impedance. BMI and waist-to-height ratio (WHR) were calculated. Associations of arterial stiffness (high PWV) with obesity and MS as defined by WHR, SM:FM, PBF, and BMI were evaluated.</p> Results <p>Participants (<i>n</i> = 67) were 15 (IQR 11, 18) years old and 39 (IQR 10, 68) months post-transplant. Participants with SM:FM-obesity (OR 3.2) and WHR-obesity (OR 3.0) had increased odds of high PWV (<i>p</i> = 0.04) while PBF-obesity (OR 2.6, <i>p</i> = 0.09) and BMI-obesity (OR 2.2, <i>p</i> = 0.17) were not significant. Participants with WHR-MS (OR 12.5, <i>p</i> = 0.02), SM:FM-MS (OR 5.2, <i>p</i> = 0.03), and PBF-MS (OR 5.0, <i>p</i> = 0.02) had increased odds of arterial stiffness, while BMI-MS was not significant (OR 3.7, <i>p</i> = 0.08).</p> Conclusions <p>Obesity is associated with arterial stiffness in a racially diverse cohort of pediatric transplant recipients. Anthropometric measures that assess body fat distribution (WHR) and body composition (SM:FM) are more strongly associated with arterial stiffness than BMI. MS has a stronger association with arterial stiffness than obesity alone, particularly when WHR is used.</p> Graphical abstract <p></p>