This editorial discussed the limitations of BMI when investigating the relationship of obesity to total mortality or cardiovascular outcomes. Although BMI is related to percent body fat, the strength of the relationship is quite moderate. Accordingly, classifying individuals based solely on this crude index of total adiposity could cause a large number of individuals to be misclassified. The editorial also emphasized that the measurement of waist circumference, which is an index of the high-risk form of obesity (abdominal obesity), should be encouraged in clinical settings as a simple risk measure.