Validity of the leg-to-leg bioimpedance to estimate changes in body fat during weight loss and regain in overweight women: A comparison with multi-compartment models

Objectives: To investigate changes in body composition and the validity of the leg-to-leg bioimpedance (LTL) method to measure body fat during active weight loss (WL) and weight regain (WR). Design: Longitudinal, 12-week weight loss intervention (3.3-3.8 MJ/day) and subsequent follow-up at 1 year. Subjects: Fifty-eight adult women aged between 24 and 65 years (mean age: 46.8±8.9 years) and with a body mass index (BMI) >25 kg/m2 (mean BMI: 31.6±2.5 kg/m2, range=26.0-48.2 kg/m2) participated in the study. Measurements: Fat mass (FM) was measured at baseline, 12 weeks, 24 weeks and 52 weeks using three- and four-compartment (4-C) models, air displacement plethysmography (ADP), deuterium dilution - total body water (TBW), dual-energy X-ray absorptiometry (DXA), skinfold thickness (SFT), tetrapolar bioelectrical impedance analysis (T-BIA) and LTL. Results: At the end of the weight loss programme, subjects lost 9.9±3.5 kg weight (P<0.001) and 7.6±0.5 kg fat (P<0.001) but after 1 year they had regained 4.9±3.7 kg of weight and 3.7±2.9 kg of fat. The 4-C model showed that FM and TBW accounted for 76.2 and 23.6% of the loss in body mass and 81.8 and 17.7% of the tissue accrued during weight regain, respectively. The estimate of body fat change by LTL relative to multi-compartment models (WL bias±2s.d.=0.51±3.26 kg; WR bias±2s.d.=-0.25±2.30 kg) was similar to ADP, DXA and TBW in both phases but it was better than T-BIA (WLbias±2s.d.= 0.17±7.90 kg; WRbias±2s.d.=-0.29±7.59 kg) and skinfold thickness (WLbias±2s.d.=2.68±6.68 kg; WR bias±2s.d.=-0.84±3.80 kg). Conclusions: Weight loss and regain were associated with minimal changes in lean tissue as measured using multi-compartment models. The LTL system is a useful method to measure body composition changes during clinical weight management programmes. © 2007 Nature Publishing Group All rights reserved.