Ethnic differences in fat and muscle mass and their implication for interpretation of bioelectrical impedance vector analysis

According to the WHO Expert Consultation, current BMI cut-offs should be retained as an international classification. There are, however, ethnic differences in BMI associated health risks that may be due to differences in body fat or skeletal muscle mass and also impact the interpretation of phase angle and bioelectrical impedance vector analysis (BIVA). Therefore the aim of this study was to compare body composition measured by bioelectrical impedance analysis between 1048 German, 1026 Mexican and 995 Japanese adults with a wide range of age and BMI (18-78years, BMI 13.9–44.3kg/m). Regression analyses between body composition parameters and BMI were used to predict ethnic-specific reference values at the standard BMI cut-offs of 18.5, 25 and 30kg/m². German men and women had a higher fat free mass per fat mass compared to Mexicans. Normal weight Japanese were similar to Mexicans but approached the German phenotype with increasing BMI. The skeletal muscle index (SMI, kg/m²) was highest in Germans whereas in BIVA the Mexican population had the longest vector, and the Japanese population had the lowest phase angle and the highest extracellular/total body water ratio. Ethnic differences in regional partitioning of fat and muscle mass at the trunk and the extremities contribute to differences in BIVA and phase angle. In conclusion, not only the relationship between BMI and adiposity is ethnic-specific but also fat distribution, SMI and muscle mass distribution vary at the same BMI. These results emphasize the need for ethnic-specific normal values in the diagnosis of obesity and sarcopenia.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author