ASSESSMENT OF BODY-COMPOSITION BY BIOELECTRICAL IMPEDANCE IN A POPULATION AGED GREATER-THAN-60-Y

Body composition was measured in a group of 35 healthy men and 37 healthy women aged 60-83 y. Body mass index (BMI) in men was 25.0 ± 2.2 kg/m2 (x̄ ± SD) and in women, 25.9 ± 3.2 kg/m2. BMI was low in relation to body fat percentage as determined by skinfold-thickness measurements or densitometry in comparison with the relation found in younger adults. Mean body fat percentage of the male subjects (aged 70.4 ± 5.2 y) as determined by densitometry was 31.0 ± 4.5%, whereas in women (aged 68.0 ± 5.2 y) it was 43.9 ± 4.3%. Body impedance correlated with fat-free mass (FFM). The best prediction formulas for the FFM from body impedance and anthropometric variables were 1) FFM (kg) = (0.671 x 104 x H2/R) + 3.1S + 3.9 where H is body height (m), R is resistance (Ω), and S is gender (females, 0; males, 1) (r = 0.94; SEE = 3.1 kg) and 2) FFM (kg) = (0.360 x 104 x H2/R) + 0.359BW + 4.5S - 20T + 7.0 where BW is body weight (kg) and T is thigh circumference (m) (r = 0.96; SEE = 2.5 kg). The prediction equations from the literature, generally determined in younger populations, overestimated FFM in elderly subjects by ~6 kg and are not applicable to elderly subjects.