ABSTRACT
The purpose of this study was to validate a bioelectrical impedance analysis (BIA) equation for prediction of body fat mass (FM) against dual energy Xray absorptiometry (DXA) in healthy Indian adults with large variations in body mass index and age. Healthy subjects (28 males and 85 females) were investigated by two methods: FM was measured by a dual energy Xray absorptiometry and segmental bioelectrical parameters at various frequencies were measured by a commercial segmental multifrequency BIA instrument. Total body parameters were derived from segmental bioelectrical parameters. As correlation was high and prediction error was low, a single equation was developed for FM as follows: FM = 15.45 + [0.0074 × (Rbody250)] - (3.89 × sex); men = 1, women = 0) + (0.844 × w) - [6938 × (h2/Zbody50)] - (22.22 × h) + [3 × (Xbody250 - Xbody5)/age)] + [1.53 × (Φbody5)] - [0.126 × (Xbody50/h)]. Fat mass predicted with dual energy Xray absorptiometry was 28.11 ± 9.30 kg. BIApredicted FM was 28.12 ± 9.11 kg (R = 0.9794, adjusted R2 = 0.9561, standard error of estimate = 1.95 kg, total error = 1.87 kg). In conclusion, the new developed BIA equation was valid for prediction of FM in healthy subjects aged 23 to 81 years with body mass indices between 15.62 and 39.98 kg.m-2. Inclusion of reactance in the kg.m-2 single prediction equation appeared to be essential for use of BIA equation in adults with large variations in body mass and age.