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

Massa livre de gordura em idosas com sobrepeso e obesidade: análise da validade concorrente de equações de impedância bioelétrica

Gislane Ferreira de Melo Daniela Rosa Américo Maria Fátima Glaner About the authors

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 device77 Lohman TG. Advances in body composition assessment. Current issues in exercise sciences series. Champaign: Human Kinetics; 1992. and those proposed by Gray et al.88 Gray DS, Bray GA, Gemayel N, Kaplan K. Effect of obesity on bioelectrical impedance. Am J Clin Nutr 1989;50(2):255-60. 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). FFMValhalla (%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 FFMGray 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.88 Gray DS, Bray GA, Gemayel N, Kaplan K. Effect of obesity on bioelectrical impedance. Am J Clin Nutr 1989;50(2):255-60. 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.

Key words
Body composition; Electrical impedance; Older adult; Test validity Validation studies

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