2009 Volume 62 Issue 5 Pages 253-258
Obesity is usually diagnosed on the basis of body mass index (BMI). Obesity, however, is defined as excessive fat volume, and not merely as being overweight. In the present study we measured BMI as well as body composition by bioimpedance analysis (BIA), and studied their relative contribution in defining obesity. BMI exhibited an almost linear correlation with fat volume, but only a modest correlation with lean body mass (LBM). The correlation of BMI with LBM was less marked in subjects with BMI ≥25 kg/m2 than in those with BMI <25 kg/m2. For the diagnosis of obesity based on body composition (percentage fat volume ≥20% for males and ≥30% for females), BMI had high specificity, but low sensitivity. In other words, a BMI exceeding 25 kg/m2 is almost always associated with obesity based on body composition. A lower BMI, however, does not rule out the presence of obesity based on body composition. Thus, nutritional assessment would be more effective if based on both BMI and body composition.
