The relationship between body mass index and body cell mass in African-American, Asian, and Caucasian adults.

The objective of this study was to investigate the relationship between body mass index (BMI, kg/m(2)) and body cell mass (BCM) estimated from total body potassium (TBK) measured by whole body (40)K counting in healthy 284 African-Americans (AA), 269 Asians (A) and 536 Caucasians (C) aged 18-107 years and to study the effects of age, sex, and race on the relationship. Body fat and fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry (DXA). There was a significant positive correlation between BCM and BMI. For a given BMI, A had lower BCM but decreased less per year of age than AA and C, and males had higher BCM than females in each ethnic group. The fraction, BCM/FFM decreased with BMI in all subgroups by race, sex, and age, and males decreased more per age and AA decrease more than A and C. Not only the BCM-BMI relationship but also BCM/FFM vs. BMI is important to health.