This study had two objectives: to determine the validity of
the leg-to-leg bioelectrical impedance (BIA) system in 1) estimating
body composition in obese and non-obese women cross-sectionally,
and 2) assessing changes in body composition in obese females
in response to 12 weeks of energy restriction and/or exercise
Subjects included 98 moderately obese females (43.2±0.6%
fat, 45.0±1.1 years) and 27 non-obese controls (24.0±1.5%
fat, 43.5±2.5 years). Obese subjects were randomly divided
into one of four groups, with fat-free mass (FFM), fat mass (FM)
and percent body fat estimated pre and post-12 weeks intervention
from BIA and underwater weighing. The four groups were diet only
(D) (4.19-5.44 MJ/day), exercise only (E)(five 45 min. sessions/week
at 78.5±0.5% maximum heart rate), both exercise and diet
(ED) and controls (C) (no diet or exercise).
No difference was found between underwater weighing and BIA
in estimating the FFM of obese and non-obese females (all subjects
combined, r=0.78, P<0.001, SEE=3.7kg), or in estimating decreases
in FM during 12 weeks of energy restriction and/or exercise among
obese subjects [F(3.85)=1.45, P=0.233].
The leg-to-leg bioelectrical impedance system accurately assessed
FFM in both obese and non-obese females, and changes in FM through
diet alone or when combined with exercise.