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Federation Proceedings, 46(4), 1987.

Assessment of fat-free mass in an older population using bioelectrical impedance.

V. A. Hughes and W. J. Evans.

USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111.

Abstract: Bioelectric impedance measurements have not been used to assess fat-free mass in an older population. We studied 36 females and 30 males (age 49 - 74 yrs, BMI: 18.4 - 34.8 kb/m^2) to determine the validity of this technique in estimating body composition in an older population. Fat-free mass (FFM) was determined by hydrodensitometry with simultaneous residual lung volume determinations. The average FFM was 36.9 ± 4.4 kg for females and 57.6 ± 5.8 kg for males. Measurements of resistance (res) and reactance (rea) were made using the BIA device. Multiple regression analysis was used to determine the best equation to predict FFM: FFM (kg) = -15.26 + .775 (ht^2/res) + .146 (wt) + .185 (rea). R = .972, p <.001, SEE = 2.65. The use of conductor length (current path length) in place of subject height did not improve the prediction accuracy of the equations. These data indicate that bioelectric impedance measurements may be used in a healthy, normally hydrated older population to estimate fat-free mass.
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