Revising BMI Cut-Off Points for Overweight and Obesity in Male Athletes: An Analysis Based on Multivariable Model-Building

Background: Body composition in athletes is characterized by pronounced muscle mass and low body fat (BF). Over and excessive adiposity are thus expected in athletes at higher body mass index (BMI) levels than those suggested by the World Health Organization (WHO). Therefore, we aimed to test the validity of WHO BMI cut-off points for overweight and obesity, respectively (i.e., >= 25 kg/m2 and 30 kg/m2) in young male athletes from different sport disciplines in Italy. Methods: This study includes 622 male young adult athletes of mean age 25.7 +/- 4.7 years who were initially categorized according to the WHO BMI classification, and then re-categorized by adiposity status based on total BF% as measured by dual-energy X-ray absorptiometry (DXA). A predictive equation has been developed utilizing multivariable model-building to predict the best BMI cut-offs for identifying overweight and obesity in this population. The agreement between the different classification systems was assessed with the kappa statistic (kappa). Results: According to the WHO BMI classification, 451 (72.5%) individuals were of normal weight, 148 (23.8%) were with overweight and 23 (3.7%) were with obesity, but based on the total BF%, 598 (96.1%) were of normal weight, and only 19 (3.1%) were with overweight and 5 (0.8%) were with obesity, revealing a weak agreement between the two classification systems (WHO BMI vs. BF%; kappa = 0.169). On the other hand, new BMI cut-off points were identified (BMI >= 28.2 kg/m2 for overweight and 33.7 kg/m2 for obesity) and showed good agreement with the BF% classification system (kappa = 0.522). Conclusions: The currently used WHO BMI cut-offs are not suitable for determining weight status in young male athletes, and since the newly proposed ones demonstrated a good performance, these should be implemented in new guidelines.