Objective: To determine the efficacy of applying specific body composition techniques to, and assess the relationship between body mass index (BMI) and body fat levels for Chinese Australian females.
Design: Statistical comparative analysis of body composition techniques.
Subjects: Australian resident females of Chinese extraction (n=40) (aged 18-45 y, mean 32.5+/-8.0; BMI range 15.7-30.9 kg/m2, mean 21.7+/-3.1 kg/m2, median 20.8 kg/m2).
Measurements: Body composition determined using bio-electrical impedance analysis (BIA), the skin-fold equations of Durnin and Womersley (D&W) and a deuterium dilution technique. Body size was calculated as the body mass index (BMI) weight/height(2) (kg/m2).
Results: With a median BMI of 20.8, range 15.7-30.9, an acceptable BMI existed for 87.5% of the subjects (mean (s.d.) 21.7+/-3.1 kg/m2). Percentage fat mass (%FM) from the deuterium dilution technique (mean (s.d.) 35.6+/-6.4) suggested 75% were overweight or obese. %FM from the D&W equation (mean (s.d.) 28.0+/-3.9) and BIA (mean (s.d.) 29.4+/-5.1) also indicated a tendency towards overweight or obese. The deuterium technique was significantly correlated and significantly different to the D&W eqn, r=0.71 P=0.001; and BIA, r=0.77, P=0.001. Bland and Altman analysis indicated that bias existed between the techniques (BIA mean (s.d.)-6.7+/-4.1) and D&W equation mean (s.d.)-6+/-4.5) when compared to the deuterium method.
Conclusions: Despite a low mean BMI, body fat levels determined by the three methods suggested that, overall, an unsatisfactory body composition existed. The levels of overweight and obesity (%FM>30) were higher than reported in previous research despite a mean BMI lower than the Australian national average. Comparative analysis suggested that the body fat prediction techniques used may be precise but not accurate. Comparative results obtained for the BIA and D&W equation techniques suggest an overestimation of body fat levels for leaner individuals and under estimation for overfat individuals. The results support the notion that accurate determination of body composition and the determination of appropriate body size may require equations developed for specific ethnic populations.