Body composition: the fat-free mass index (FFMI) and the body fat mass index (BFMI) distribution among the adult Austrian population - results of a cross-sectional pilot study

Objective: It has been proven that low and high body mass index (BMI) values increase health risks and mortality, and are associated with variations in fat-free mass (FFM) and body fat mass (BF). Fat-free mass index (FFMI; kg/m2) and body fat mass index (BFMI; kg/m2) however are better measures of body composition. FFMI and BFMI being age-, sex- and population-specific, are more exact and informative measures. The purpose of this pilot study was to determine FFMI and BFMI values in subjects with normal, overweight, and obese BMI in Austria. Methods: We measured the levels of FFM and BF in 153 healthy Caucasian men and 451 healthy Caucasian women between the ages of 18 to 80 years, using multi-frequency bioelectrical impedance analysis. FFMI, BFMI, and %BF were then calculated for each subject. Results: Predicted FFMI values were 18.1 to 21.7 kg/m2 for men and 15.1 to 17 kg/m2 for women within the normal BMI ranges (18.5-24.9 kg/m2). Predicted BFMI values were 1.5 to 5.0 kg/m2 for men and 3.4 to 8.0 kg/m2 for women within the normal BMI ranges. BFMI values were above 8.0 and 11.7 kg/m2 in men and women, respectively, for obese BMI (>30 kg/m2). Normal ranges for %BF were 11.9 to 22.7 and 20.8 to 31.0 for men and women, respectively. Conclusion: A major finding of this study was that a significant number of individuals had a lower FFMI and a higher FMI than predicted for their weight indicating the necessity of body composition measurements in the clinical practice to optimize diagnosis and treatment.