A comparison of skinfold thickness, body mass index, bioelectrical impedance analysis and dual-energy X-ray absorptiometry in assessing body composition in obese subjects before and after weight loss.

The assessment of body composition in obese subjects by anthropometric means (skinfolds), presents many difficulties. This study compares the estimates provided of fat free mass in 21 obese subjects (mean body mass index 36.6 +/- 1.2 kg/m(2)) using body mass index and skinfold thickness, with those obtained using the more recently developed techniques of bioelectrical impedance analysis and dual-energy X-ray absorptiometry. Despite highly significant correlations between some of the methods (r(2) = 0.94 for dual-energy X-ray absorptiometry versus bioelectrical impedance analysis), there was a considerable lack of agreement in the measurements, particularly when skinfold thickness was compared with dual-energy X-ray absorptiometry (limits of agreement -21.9 to -1.5 kg for fat free mass estimated from dual-energy X-ray absorptiometry and skinfold thickness) and even for dual-energy X-ray absorptiometry and bioelectrical impedance analysis (limits of agreement -10.7 to 0.4 kg). After weight loss the intermethod differences were reduced.