Why RJL Systems Uses Hand to Foot BIA

RJL Systems BIA testing protocol uses a hand to foot measurement because it has been shown to be far superior to hand to hand and foot to foot measurements. The papers listed below illustrate the failings of hand to hand and foot to foot BIA methods.


J Nutr. 2001 May;131(5):1589S-95S.

Selected body composition methods can be used in field studies.

Ellis KJ.

Body Composition Laboratory, U.S. Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA.

This article provides an overview of the present status of in vivo body composition methodologies that have potential for use in field studies. The methods are divided into four general categories: anthropometric indices and skinfold, body volume measurements, body water measurements including bioelectrical methods, and imaging techniques. Among the newest technologies are air-displacement plethysmography, three-dimensional photonic scanning, multifrequency bioelectrical impedance spectroscopy and whole-body tomography using electrical impedance and magnetic induction. These newer approaches are compared with the established reference methods. The advantages and limitations of each technique as a field method are presented relative to the corresponding concepts of an ideal method.


Nutrition. 2003 Oct;19(10):851-7.

Validity and accuracy of regional bioelectrical impedance devices to determine whole-body fatness.

Lukaski HC, Siders WA.

US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, North Dakota 58202-9034, USA. hlukaski@gfhnrc.ars.usda.gov

OBJECTIVE: Growing emphasis on obesity as a risk factor for chronic diseases and commercial availability of impedance devices for the at-home assessment of body fatness have stimulated the need for a critical evaluation of the validity of these instruments. This study determined the reproducibility and accuracy of two commercial impedance devices that use upper (hand-to-hand) or lower (foot-to-foot) body contact electrode placements in adults with a wide range of body fatness. METHODS: Body composition was assessed with dual x-ray absorptiometry in apparently healthy adults (62 women and 48 men) ages 21 to 60 y, with a range in body mass index of 18.6 to 40.5 kg/m2. Variability in body fatness predicted with the regional body impedance devices was determined in 10 adults on 5 consecutive d. A 50-kHz, tetrapolar bioelectrical impedance plethysmograph with surface electrode placements on the upper and lower limbs was used to determine reference regional and whole-body impedance values. RESULTS: Variability in body mass (1%) over 5 d was less than body fatness predicted with the upper (2-10%) and lower (3-5%) body devices. Regional and whole-body impedance values were different (P < 0.05) in the women, whereas upper and lower body values were lower (P < 0.05) than whole-body impedance in the men. Dual x-ray absorptiometric determinations of body fatness were similar to predictions based on models derived from physical characteristics (age, stature, body mass, and sex) but significantly different (P < 0.05) from estimates from the impedance devices, which underestimated body fatness. Bias in predictions of body fatness with the regional devices was systematically (P < 0.0001) related to body fatness. CONCLUSION: Use of regional impedance devices to assess body fatness is limited by a lack of precision and accuracy.


Am J Hum Biol. 2007 May-Jun;19(3):429-33.

Validation of hand-held bioelectrical impedance analysis with magnetic resonance imaging for the assessment of body composition in overweight women.

Varady KA, Santosa S, Jones PJ.

School of Dietetics and Human Nutrition, McGill University, Qu├ębec, Canada.

Methods of assessing body composition suitable for use in clinical trials should be accurate, reliable, and easy to perform. One such technique routinely implemented is hand-held bioelectrical impedance analysis (BIA). The validity of this method, however, in body composition assessment of overweight women is not known. The aim of this study was to validate the hand-held BIA technique with magnetic resonance imaging (MRI) for the assessment of body composition in overweight women. Fat mass, percent fat mass, fat-free mass, and percent fat-free mass values estimated by hand-held BIA were compared to those measured by MRI. Thirty-one Caucasian women (50.1 +/- 8.2 years, body mass index of 26.9 +/- 3.1 kg/m(2)) participated in the study. BIA measurements were highly reproducible (technical error (TE) was 0.06 +/- 0.07 kg for fat mass and 0.08 +/- 0.11% for percent fat mass), but were significantly different (P < 0.0001) for each body composition parameter when compared to MRI. BIA underestimated fat mass by 2.3 +/- 3.3 kg and percent fat mass by 5.6 +/- 3.9%. Likewise, BIA overestimated fat free mass by 7.4 +/- 2.7 kg and percent fat free mass by 5.6 +/- 3.2%. No relationship between the bias and the mean of the two measurements was noted suggesting that bias is not related to measurement size. Although hand-held BIA gives reproducible findings, the bias noted for all body composition parameters puts into question the validity of this regional impedance device for use in clinical trials in overweight women. Copyright 2007 Wiley-Liss, Inc.


J Physiol Anthropol Appl Human Sci. 2004 May;23(3):93-9.

Percentage of total body fat as estimated by three automatic bioelectrical impedance analyzers.

Demura S, Sato S, Kitabayashi T.

Kanazawa University, Faculty of Education.

The present study aimed to compare the accuracy of estimating the percentage of total body fat (%TBF) among three bioelectrical impedance analysis (BIA) devices: a single-frequency BIA with four tactile electrodes (SF-BIA4), a single-frequency BIA with eight tactile electrodes (SF-BIA8) and a multi-frequency BIA with eight tactile electrodes (MF-BIA8). Dual-energy x-ray absorptiometry (DXA) and hydrostatic weighing (HW) were used as references for the measured values. Forty-five healthy college student volunteers (21 males: 172.9 +/- 5.5 cm and 65.8 +/- 9.1 kg and 24 females: 160.7 +/- 6.6 cm, 52.6 +/- 6.2 kg) were the subjects. Correlation coefficients between the BIA measurements and the references were calculated. The standard error of estimation (SEE) was calculated by regression analysis when estimating the reference measures (DXA and HW) from the predictor (SF-BIA4, SF-BIA8 and MF-BIA8). The differences in %TBF between the reference and the predictor, calculated by the reference minus the predictor, were plotted against the %TBF measured by the references. The MF-BIA 8 here showed the highest correspondence to the reference and the least estimation error compared with the other BIA methods. It is considered that there is a limit to directly estimate FFM from a regression equation using impedance, weight, height and age as independent variables, and that %TBF can be more accurately estimated by measuring segmental impedances using eight electrodes and multi-frequency electric currents and then estimating total body water from these impedances.


Int J Body Compos Res. 2006;4(4):153-160.

Comparison of two bioelectrical impedance analysis instruments for determining body composition in adolescent girls.

Nichols J, Going S, Loftin M, Stewart D, Nowicki E, Pickrel J.

San Diego State University, San Diego, CA.

The purpose of this study was to compare fat-free mass (FFM) and percent body fat determined by two bio-electrical impedance analysis (BIA) instruments against criterion estimates determined by dual-energy x-ray absorptiometry (DXA) in a multi-racial/ethnic sample of adolescent girls. BIA was assessed in 151 girls (n=51 African-American; n=45 Hispanic; n=55 Caucasian; age 12.2 +/- 1.2 yr) using the RJL Quantum II and the American Weights and Measures Body-Comp Scale (BCS). Percent body fat determined by BIA was significantly related to that determined by DXA (R(2)=0.87, SEE=2.8% for RJL vs DXA, P<0.0001; R(2)=0.71, SEE=4.4% for BCS vs DXA, P<0.0001). The agreement between DXA and BIA for FFM was also significant (R(2)=0.91, SEE=0.03 kg for RJL, P <0.0001; R(2)=0.79, SEE=0.04 kg for BCS, P <0.0001). The BCS overestimated FFM by 2.7 kg (P<0.0001) and underestimated percent body fat by over 4% (P<0.001). There were no differences in percent body fat between DXA and the RJL, and although the RJL significantly overestimated FFM, the absolute difference was <1 kg. Within each ethnic group, the RJL instrument more closely estimated FFM and percent body fat than did the BCS. Although both BIA instruments compared favorably with DXA, the RJL had better stability and accuracy than the BCS, for both the total sample and for the three ethnic groups. Considering its relatively low cost and minimal time required for technical training, BIA is a useful and appropriate technique for assessing body composition in adolescent girls.


J Athl Train. 2006 Jan-Mar;41(1):46-51.

A comparison of bioelectrical impedance and skinfold measurements in determining minimum wrestling weights in high school wrestlers.

Hetzler RK, Kimura IF, Haines K, Labotz M, Smith J.

University of Hawaii, Manoa, Honolulu, HI 96822, USA.

CONTEXT: Whether bioelectrical impedance and skinfold analysis can be used interchangeably to establish minimal wrestling weights (MWWs) is unknown. Using both methods in a particular program may result in the misclassification of some athletes. OBJECTIVE: To compare the MWW calculated from skinfold measurements with those derived from 5 bioelectrical impedance equations and determine if the 2 methods could be used interchangeably for high school wrestlers. DESIGN: Repeated measurements were obtained using bioelectrical impedance and skinfold analysis to determine MWWs. Data were collected during the preseason. SETTING: High school. PATIENTS OR OTHER PARTICIPANTS: Two hundred eight wrestlers (151 males, 57 females), aged 13 to 18 years. MAIN OUTCOME MEASURE(S): The bioelectrical impedance analysis was conducted with the MWW protocol administered annually by certified athletic trainers. The resistance and reactance were used in 5 equations to investigate the level of agreement between bioelectrical impedance and skinfold analysis for determining MWW. The MWWs were based on a minimum body fat of 7.0% for males and 14.0% for females. RESULTS: When comparing bioelectrical impedance and skinfold analysis, we found prediction error ranged from 1.51 to 2.34 kg for males and 0.27 to 9.16 kg for females. CONCLUSIONS: To protect the health of the athletes and maintain competitive equity, a single method should be used to determine MWWs. Bioelectrical impedance and skinfold analysis cannot be used interchangeably to determine MWWs.


Obesity (Silver Spring). 2007 Jan;15(1):85-92.

Bioelectrical impedance vs. four-compartment model to assess body fat change in overweight adults.

Chouinard LE, Schoeller DA, Watras AC, Clark RR, Close RN, Buchholz AC.

Department of Family Relations and Applied Nutrition, University of Guelph, 50 Stone Road E, Guelph, Ontario, Canada N1G 2W1.

OBJECTIVE: The Tanita TBF-305 body fat analyzer is marketed for home and clinical use and is based on the principles of leg-to-leg bioelectrical impedance analysis (BIA). Few studies have investigated the ability of leg-to-leg BIA to detect change in percentage fat mass (%FM) over time. Our objective was to determine the ability of leg-to-leg BIA vs. the four-compartment (4C) model to detect small changes in %FM in overweight adults. RESEARCH METHODS AND PROCEDURES: Thirty-eight overweight adults (BMI, 25.0 to 29.9 kg/m2; age, 18 to 44 years; 31 women) participated in a 6-month, randomized, double-blind, placebo-controlled study of a nutritional supplement. Body composition was measured at 0 and 6 months using the Tanita TBF-305 body fat analyzer [using equations derived by the manufacturer (%FM(T-Man)) and by Jebb et al. (%FM(T-Jebb))] and the 4C model (%FM(4C)). RESULTS: Subjects in the experimental group lost 0.9%FM(4C) (p = 0.03), a loss that did not reach significance using leg-to-leg BIA (0.6%FM(T-Man), p = 0.151; 0.6%FM(T-Jebb), p = 0.144). We observed large standard deviations (SDs) in the mean difference in %FM between the 4C model and the Tanita(Manufacturer) (2.5%) and Tanita(Jebb) (2.2%). Ten subjects fell outside +/-1 SD of the mean differences at 0 and 6 months; those individuals were younger and shorter than those within +/-1 SD. DISCUSSION: Leg-to-leg BIA performed reasonably well in predicting decreases in %FM in this group of overweight adults but resulted in wide SDs vs. %FM(4C) in individuals. Cross-sectional determinations of %FM of overweight individuals using leg-to-leg BIA should be interpreted with caution.


These papers and abstracts of papers have been published in peer-reviewed journals. They may draw conclusions and discuss applications of Bioelectrical Impedance Analysis which have not been reviewed by the FDA. Statements made within them are the sole responsibility of the authors. Unless otherwise indicated, no material support was provided to the authors or study investigators by RJL Systems.