Abstract: Body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) thresholds have been calibrated to assess risk of obesity-related comorbidities and mortality, with the working definition of obesity (BMI ≥30) commonly used by health agencies, including the World Health Organization, Centers for Disease Control and Prevention, and National Institutes of Health.1,2 However, BMI does not account for sex, age, body frame, race and ethnicity, or genetic variability, which may affect susceptibility to metabolic disease.3,4 Absolute BMI does not account for metabolic effects of BMI changes. Nonetheless, current eligibility criteria for metabolic and bariatric surgery are based on BMI thresholds.5 The American Medical Association highlighted BMI limitations, suggesting that it is “…an imperfect way to measure body fat in multiple groups.”6 This study identifies populations whose risk for obesity-related metabolic comorbidities may be misclassified by standard BMI thresholds.