Objective: To assess the accuracy of body mass index (BMI) as a measure of obesity compared with percent body fat (%BF) directly measured by dual energy x-ray absorptiometry among retired football players.
Methods: The level of agreement between BMI and %BF as measures of obesity was assessed by sensitivity, specificity, and the kappa statistic among 129 retired football players. Logistic regression was used to investigate the association between obesity and selected comorbidities.
Results: Using BMI 30 kg/m2 or higher to identify obesity had poor specificity (0.36): 87 of 129 subjects were classified as obese, yet only 13 were truly obese based on %BF. Although BMI did not reliably indicate true %BF-obesity, BMI-obesity was significantly correlated with lineman position (P < 0.0001), years played (P = 0.03), and obstructive sleep apnea (P = 0.0005).
Conclusions: Percent body fat measured by dual energy x-ray absorptiometry provides a more accurate measure of obesity than does BMI among retired football players.