Fat-free mass in overweight and obese older women: analysis of concurrent validity of bioelectrical impedance equations

Abstract

Older adults, especially women, show a higher level of functional dependence and disability because of muscle and bone mass loss and of a progressive increase in body fat mass. These changes in body composition components have been observed by different techniques. The aim of this study was to analyze the concurrent validity of bioelectrical impedance equations obtained with the Valhalla device7 and those proposed by Gray et al. for the estimation of fat-free mass (FFM) in Brazilian elderly women. The sample (n=34; 60-71 years old, height of 140-162 cm) was divided into two groups (n=17) according to relative body fat (%BF) obtained by DXA: %BF ?41 and %BF >41. DXA was used as the gold standard. All correlation coefficients were satisfactory (r>0.79). FFM Valhalla (%BF ?41: 36.1±3.4 kg; %BF >41: 39.3±3.2 kg) did not differ (p>0.01) from FFMDXA (38.7±3.7 kg) in either group. However, the standard error of the estimate (SEE) was slightly higher (2.114 kg) than the recommended one in the %BF >41 group. FFMGray differed (p<0.01) from FFMDXA in the two groups, although the SEE was satisfactory (<1.8 kg) in the %BF ?41 group. The residual scores indicated the absence of agreement between FFM Gray and FFMDXA, reaching 7.08 kg. Only 9% of the subjects had FFM estimated within an acceptable error when the equation of Gray et al. was used, while this percentage was 82% when the Valhalla equation was used. The latter equation showed concurrent validity for overweight and obese older women