Bioelectrical Impedance Analysis Equations Research Articles

Estimation of total body water and extracellular water with bioimpedance in athletes: A need for athlete-specific prediction models

Bioelectrical impedance analysis (BIA) equations can predict total body water (TBW) and extracellular water (ECW) in non-athletic healthy populations. This study aimed: a) to develop BIA-based models for TBW and ECW prediction based on dilution methods in a sample of national level athletes; and b) to validate the new models with a cross-validation approach in a separate cohort using dilution methods as criterion. Two hundred and eight highly trained athletes (21.3±5.0 years) were evaluated during their respective competitive seasons. Athletes were randomly split into development (n=139) and validation groups (n=69). The criterion method for TBW was deuterium dilution and for ECW was bromide dilution, where ICW was the respective difference between both. Resistance (R) and reactance (Xc) were obtained with a phase-sensitive 50kHz BIA device and used for the estimation of TBW and ECW. Athletic BIA-based models were developed for TBW and ECW [TBW=0.286+0.195*S(2)/R+0.385*Wt+5.086*Sex; ECW=1.579+0.055*S(2)/R+0.127*Wt+0.006*S(2)/Xc+0.932*Sex, where sex is 0 if female or 1 if male, Wt is weight (kg), S is stature (cm), and R and Xc are in ohm (Ω)]. Cross validation revealed R(2) of 0.91 for TBW and R(2) 0.70 for ECW and no mean bias. The new equations can be considered valid, with no observed bias, thus affording practical means to quantify TBW and ECW in national level athletes.

Assessing appendicular skeletal muscle mass with bioelectrical impedance analysis in free-living Caucasian older adults

Aging is characterized by a loss of appendicular skeletal muscle mass (ASMM) leading to physical disability and death. Bioelectrical impedance analysis (BIA) is reliable in estimating ASMM but no prediction equations are available for elderly Caucasian subjects. The aim of the study was to develop and validate an equation derived from bioelectrical impedance analysis (BIA) to predict appendicular skeletal muscle mass (ASMM) in healthy Caucasian elderly subjects, taking dual X-ray absorptiometry (DXA) as the reference method, and comparing the reliability of the new equation with another BIA-based model developed by Kyle et al. (Kyle UG, Genton L, Hans D, Pichard C, 2003). With a cross-sectional design, 296 free-living, healthy Caucasian subjects (117 men, 179 women) over 60 years of age were enrolled. Lean mass of limbs was measured with DXA to ascertain ASMM (ASMMDxA). Whole-body tetrapolar BIA was performed to measure resistance (Rz), resistance normalized for stature (RI), and reactance (Xc). The BIA multiple regression equation for predicting ASMM was developed using a double cross-validation technique. The predicted ASMM values were compared with ASMMKyle, i.e. ASMM estimates derived from the model developed by Kyle et al. (Kyle et al., 2003). Cross-validation resulted in a unique equation using the whole sample: ASMM (kg) = -3.964 + (0.227*RI) + (0.095*weight) + (1.384*sex) + (0.064*Xc) [R(2) = 0.92 and SEE = 1.14 kg]. In our sample, ASMMKyle differed significantly from the ASMMDxA (p < 0.0001), with a mean error of -0.97 ± 1.34 kg (5.1 ± 6.9%). Unlike the present BIA prediction equation, the Kyle et al. model showed a correlation between the bias and the mean of ASMMDxA and ASMMKyle (r = -0.406, p < 0.001). The new BIA equation provides a valid estimate of ASMM in older Caucasian adults.

Comparison of Bioimpedance and Clinical Methods for Dry Weight Prediction in Maintenance Hemodialysis Patients

Background: Bioelectrical impedance analysis (BIA) is a promising technique to evaluate dry weight. We compared the dry weight calculated by the three BIA equations Carlo Basile (CB) , Yanna Dou (YD) and the body composition spectroscopy (BCS) with clinical evaluation in maintenance hemodialysis (MHD) patients. Methods: The dry weight of enrolled MHD patients (DW_Clin) was evaluated under strict clinical surveillance. The whole-body resistances at 50 kHz, intra- and extracellular resistances were measured to calculate the dry weight (DW_CB, DW_YD and DW_BCS) using each of the three equations. Results: Neither DW_CB nor DW_BCS were statistically different compared to DW_Clin (DW_CB 63.2 ± 17.2 vs. 63.1 ± 16.1 kg; DW_BCS 62.8 ± 16.8 vs. 63.1 ± 16.1 kg, p > 0.05). DW_YD was significantly lower than DW_Clin (DW_YD 62.0 ± 16.1 vs. 63.1 ± 16.1 kg, p < 0.05). The bias between DW_CB and DW_Clin was the smallest among these three methods (ΔDW_CB -0.1 ± 1.4 kg; ΔDW_YD 1.1 ± 2.9 kg; ΔDW_BCS 0.3 ± 1.8 kg). Conclusion: The CB equations have better consistency with clinical dry weight in MHD patients.

Validity of bioelectrical impedance measurement in predicting fat-free mass of Chinese children and adolescents.

BackgroundThe current study aimed to examine the validity of various published bioelectrical impedance analysis (BIA) equations in estimating FFM among Chinese children and adolescents and to develop BIA equations for the estimation of fat-free mass (FFM) appropriate for Chinese children and adolescents.Material/MethodsA total of 255 healthy Chinese children and adolescents aged 9 to 19 years old (127 males and 128 females) from Tianjin, China, participated in the BIA measurement at 50 kHz between the hand and the foot. The criterion measure of FFM was also employed using dual-energy X-ray absorptiometry (DEXA). FFM estimated from 24 published BIA equations was cross-validated against the criterion measure from DEXA. Multiple linear regression was conducted to examine alternative BIA equation for the studied population.ResultsFFM estimated from the 24 published BIA equations yielded high correlations with the directly measured FFM from DEXA. However, none of the 24 equations was statistically equivalent with the DEXA-measured FFM. Using multiple linear regression and cross-validation against DEXA measurement, an alternative prediction equation was determined as follows: FFM (kg)=1.613+0.742×height (cm)2/impedance (Ω)+0.151×body weight (kg); R2=0.95; SEE=2.45kg; CV=6.5, 93.7% of the residuals of all the participants fell within the 95% limits of agreement.ConclusionsBIA was highly correlated with FFM in Chinese children and adolescents. When the new developed BIA equations are applied, BIA can provide a practical and valid measurement of body composition in Chinese children and adolescents.

Assessment of appendicular skeletal muscle mass by bioimpedance in older community-dwelling Korean adults

It is crucial to investigate age-related body composition changes in geriatric medicine. Bioelectrical impedance analysis (BIA) is easy to perform, non-invasive, relatively inexpensive, and portable. However, the accuracy of measurement by BIA is questionable. To develop and cross-validate the predictive equation for estimated appendicular skeletal muscle mass (ASM) using BIA in older community-dwelling Korean adults, we include two cohorts: study participants aged 65–80 years in the Ansung cohort for the Korean Health and Genome Study (men, n=285; women, n=435) used as equation-generating group, and Korean Longitudinal Study of Health Aging (KLoSHA) as cross-validation group (men, n=202; women, n=208). Dual energy X-ray absorptiometry (DXA) and BIA were performed in both cohorts. Using multiple linear regression analysis, we drew a predictive equation for DXA-measured ASM by BIA resistance. From DXA and BIA measurements in the Ansung cohort, we generated the estimated equation ASM (kg)=[(Ht2/R×0.104)+(age×−0.050)+(gender×2.954)+(weight×0.055)]+5.663 where Ht is height in centimeters; R is BIA resistance in 250Ω; for gender, men=1 and women=0; and age is in years. We validated this equation in the KLoSHA. The r2 of the estimated ASM was 0.890. This BIA equation provides valid estimates of ASM in older Korean adults.

Development and validation of bioelectrical impedance analysis equations for predicting total body water and fat-free mass in North-African adults.

Accuracy of the bioelectrical impedance analysis (BIA) depends on population-specific prediction equations. The aim of our study was to develop prediction equations for assessing total body water (TBW) and fat-free mass (FFM) in healthy North-African adults. In all, 250 participants (194 women, 56 men) aged 18-64 years were included in the analysis. BIA variables were measured by a tetra-polar device. TBW and FFM were assessed by the dilution of deuterium (D2O). The participants were sorted by gender and randomly split into development and validation subgroups. The validity of other published equations was also tested using Bland and Altman procedure, proportional bias and pure error. The prediction equations derived were: TBW (l)=5.68+0.267 height(2)/resistance+4.42 sex (male=1, female=0) + 0.225 weight-0.052 age (R(2)=0.92, root mean square error (RMSE)=1.75 l, RMSE%=5.65); and FFM (kg)=7.47 + 0.366 height(2)/resistance+6.04 sex + 0.306 weight-0.063 age (R(2)=0.92, RMSE=2.38 kg, RMSE%=5.61). The new equations provided nonsignificant proportional bias values, and better agreement than other tested equations. Bias and pure error values were 0.36 and 1.88 l for men and 0.00 and 1.82 l for women, for TBW equation. For FFM equation, bias values were 0.43 and -0.04 kg, and pure errors were 2.57 and 2.46 kg for men and women, respectively. The new prediction equations provide reliable estimates of TBW and FFM in North-African adults and are recommended for use in these populations.

Body composition in urban South Asian women; development of a bioelectrical impedance analysis prediction equation

Background: Assessment of body composition plays a significant role in combating chronic disease among South Asians. Accurate assessment of body composition by bioelectrical impedance analysis (BIA) requires population-specific equations which are currently unavailable for urban South Asian women.Aim: To assess validity of direct BIA assessment and selected equations for prediction of total body water (TBW), against Deuterium (2H2O) dilution and develop and validate a population-specific TBW equation for urban South Asian women.Subjects and method: Data of 80 urban Sri Lankan women (30–45 years) were used for this analysis. Body composition was assessed by 2H2O dilution (reference) and BIA. Available BIA equations were assessed for validity. A new TBW equation was generated and validated.Results: Direct BIA measurements and other equations did not meet validation criteria in predicting TBW. TBW by the new equation (TBW = 3.443 + 0.342 × (height2/impedance) + 0.176 × weight) correlated (p < 0.001) with TBW by reference method. TBW using the new equation was not significantly different (25.30 ± 2.4 kg) from the reference (25.32 ± 2.7 kg).Conclusion: Direct use of TBW by instrument and existing equations are less suitable for this population. The new TBW equation is suitable for body composition assessment in urban South Asian women.

Skeletal muscle mass in hospitalized elderly patients: Comparison of measurements by single-frequency BIA and DXA

There is increasing interest in estimating skeletal muscle mass (SMM) in clinical practice. We aimed to validate a bioelectrical impedance analysis (BIA) prediction equation for SMM, developed in a different healthy elderly population, in a population of hospital patients aged 70 and over, by comparison with dual-energy X-ray absorptiometry (DXA) SMM estimates. Comparison was also made with two other previously published BIA muscle prediction equations. Muscle measurements by BIA and DXA were compared in 117 patients with a range of clinical conditions (45 female, 72 male, mean age 75 years). The BIA equation used yielded an accurate estimate of DXA-derived SMM. Mean (SD) difference was 0.26(1.79) kg (ns). The two other BIA equations over-estimated SMM compared to DXA (both p < 0.001), but all equations were highly correlated. The BIA equation used, developed in a different healthy elderly population, gave an accurate estimate of DXA-derived SMM in a population with various clinical disorders. BIA appears potentially capable to estimate SMM in clinical disorders, but the optimal approach to its use for this purpose requires further investigation.

Response to Letter to the Editor from Dr. Safer et al. regarding the article “Age-related changes in body composition in a sample of Czech women aged 18–89 years: a cross-sectional study,” published in European Journal of Nutrition

We appreciate that Dr. Umut Safer and his colleagues considered our study [1] interesting and recommended it to readers of the European Journal of Nutrition. With regards to the letter from Safer et al. about our recent publication, our responses to the letter are as follows. In the Letter to the Editor, Safer et al. argued that pretesting preparation is necessary to maximize the accuracy of the direct segmental multi-frequency bioelectrical impedance analysis (BIA). We agree with this statement and guarantee that all participants were asked to fast for 2 h, to avoid any vigorous physical activity for at least 48 h before the procedure, and to urinate or defecate before the measurements were taken. To comply with the standard conditions of measurement, we excluded those who use diuretics or are undergoing diuretic therapy. Safer et al. have noted in their letter that we calculated fat-free mass (FFM) by an equation based on total body water (TBW) measurement, but this was not referenced. We would like to respond to this comment. In ‘‘Methods,’’ we described the principles for estimate body composition via BIA. According to Thibault et al. [2], the measurement of total body impedance allows estimation of TBW, and, by assuming that TBW is constant, FFM which contains body water. InBody 720 (Biospace Co., Ltd.; Seoul, Korea) estimates FFM by dividing TBW by constant. TBW was estimated from area, volume, length, impedance, and a constant proportion. In contrast to single-frequency devices, InBody 720 uses multiple-frequency technology which improves the estimation of FFM, and, hence, body fat, by determining intracellular and extracellular water. Finally, Safer et al. highlighted that validity of segmental multi-frequency BIA was referenced by the study of Ling et al. [3] that describes Korean middle-aged adult population. We dare to disagree with this statement because the study sample of the study mentioned above includes participants from Leiden Longevity Study (Netherlands). Although Mally et al. [4] reported that actual BIA equations should be revised, we have to point out that the authors of the study used single-frequency device (Tanita BC-418 MA) and the study participants were over 60 years old. And hence, this conclusion should not be generalized for all BIA devices and all age groups.

Bioelectrical impedance analysis (BIA) equations validation against hydrodensitometry in a Colombian population

Several studies have shown that the accuracy of BIA results depends of ethnicity, age, gender, hormonal and genetic variations and, so far, there are not specific equations for Colombian population. The purpose was to evaluate reported BIA equations to determine their usefulness in body composition assessment in young females from Colombia using hydrodensitometry as the reference method. A sample of 30 young females was evaluated. Inclusion and exclusion criteria were defined to minimize the variability of BIA. Height, weight, multi-frequency BIA, residual lung volume (RV) and underwater weight (UWW) were measured. Five BIA equations met the inclusion criteria of this study. Three equations overestimated and two equations underestimated body fat (BF). Paired Student t-test and Bland and Altman analysis (p<0.05) showed significant differences in four BIA equations. However, all standard error of estimate (SEE) to BF was greater than 2.7 kg. This study showed that the five selected BIA equations are not valid for estimation of body composition in young females from Colombia. It is recommended to develop BIA equations to improve BF fat assessment in our population.

Preliminary bioelectrical impedance analysis (BIA) equation for body composition assessment in young females from Colombia

A previous study showed that reported BIA equations for body composition are not suitable for Colombian population. The purpose of this study was to develop and validate a preliminary BIA equation for body composition assessment in young females from Colombia, using hydrodensitometry as reference method. A sample of 30 young females was evaluated. Inclusion and exclusion criteria were defined to minimize the variability of BIA. Height, weight, BIA, residual lung volume (RV) and underwater weight (UWW) were measured. A preliminary BIA equation was developed (r2 = 0.72, SEE = 2.48 kg) by stepwise multiple regression with fat-free mass (FFM) as dependent variable and weight, height and impedance measurements as independent variables. The quality of regression was evaluated and a cross-validation against 50% of sample confirmed that results obtained with the preliminary BIA equation is interchangeable with results obtained with hydrodensitometry (r2 = 0.84, SEE = 2.62 kg). The preliminary BIA equation can be used for body composition assessment in young females from Colombia until a definitive equation is developed. The next step will be increasing the sample, including a second reference method, as deuterium oxide dilution (D2O), and using multi-frequency BIA (MF-BIA). It would also be desirable to develop equations for males and other ethnic groups in Colombia.

Comparison of DEXA-derived body fat measurement to two race-specific bioelectrical impedance equations in healthy Indians

AimPrevalence of obesity is increasing in Asian Indians. Reliable, precise and convenient methods to estimate body composition are required. This study aimed to test the accuracy of bioelectrical impedance analysis (BIA) estimates of body composition among Asian Indians according to two BIA equations – one developed for Asians, the other for Caucasians. MethodsTwo hundred apparently healthy Asian Indians (100 males, 100 females; mean age 36.6±7.6 years; mean BMI 16.6–46.7kg/m2) underwent BIA assessment of fat mass (FM), fat free mass (FFM) and percentage body fat (%BF) using Tanita Multi-Frequency Body Composition Analyzer MC-180MA (Tanita Corporation, Tokyo, Japan). One set of BIA values was automatically calculated by the analyzer (Caucasian figures), the other set by Tanita (Japanese Asian figures). Results were compared to dual X-ray absorptiometry (DEXA) as the standard measure. ResultsA moderate level of relative agreement was found between the DEXA-derived measurement of %BF and the estimate from both the Caucasian (r2=0.75; p<0.001) and Asian equation (r2=0.7; p<0.001). Despite this, the level of absolute agreement was poor, with large bias and wide limits of agreement. According to the Caucasian equation the mean difference between methods was −8.3±3.9 (95% limits of agreement −20.10 to 9.40), for the Asian equations mean difference was −5.4±4.3 (95% limits of agreement −20.63 to 11.41). Interpretation and conclusionsWhen compared to DEXA, the current Asian and Caucasian Tanita formulae significantly under-estimate the %BF of Asian Indians.

Body Composition in Prepubertal, HIV‐Infected Children

The aim of this study was to compare bioelectrical impedance analysis (BIA) equations developed for healthy pediatric populations and for HIV-infected children using dual-energy X-ray absorptiometry (DXA) as the gold standard. A cross-sectional study was carried out with 40 prepubertal, HIV-infected children who regularly attended the Pediatric Infectious Disease Clinic at the Universidade Federal de São Paulo, São Paulo, Brazil. The study was conducted from August to November 2008. Demographic data, clinical parameters, immunological status, and use of antiretroviral therapy were obtained from the patients' medical records. We performed anthropometric parameters and body composition analyses, analyzed body composition by BIA and DXA, and compared the results obtained from BIA through using equations for both healthy and HIV-infected populations. The mean ± SD age of the study population was 9.8 ± 1.2 years. Half of the population were females, and 82.5% of the children were clinically classified as B and C. Total body fat, by both absolute mass and by percentage, exhibited high homogeneity between the results obtained from BIA and DXA. However, there was no concordance in fat-free mass. The equation for healthy children showed good sensitivity and specificity when comparing the percentage of total body fat measured by DXA. BIA provides reliable data on total body fat but not fat-free mass when compared with DXA. The BIA equation developed for healthy pediatric populations can be used to determine total body fat in HIV-infected children.

Tracking fat-free mass changes in elderly men and women using single-frequency bioimpedance and dual-energy X-ray absorptiometry: a four-compartment model comparison

To compare single estimations of fat-free mass (FFM) and to track FFM using single-frequency bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) compared with a four-compartment (4C) model in healthy elderly Americans. Thirty-four men and thirty-eight women (Caucasian, ≥ 65 years) were included in the study. Subjects participated in either the control group or the exercise group. All testing and training took place during the 21-week investigation. Body composition assessments using nine BIA equations, DXA and a 4C model were performed during weeks 1, 12 and 24 of the study. Single estimations for DXA and BIA produced high r values (0.79-0.95) and low standard error of estimate values (1.62-3.3 kg), producing subjective ratings of 'ideal' for men and 'excellent' for women. Both DXA and two BIA equations revealed the same significance when comparing groups and times with the 4C model. Individual accuracy for tracking changes was similar among BIA equations and DXA compared with the 4C model, with a total agreement of 25% for BIA and 27% for DXA compared with the 4C model. The current data in combination with the reliability errors for both BIA and DXA FFM estimations suggest that individual results should be interpreted with caution if FFM changes are <5 kg. However, DXA and BIA are both valid methods that can be used interchangeably to estimate FFM at a single time point or for tracking changes in FFM in small groups (15-22) of healthy American older adults.

What makes a BIA equation unique? Validity of eight-electrode multifrequency BIA to estimate body composition in a healthy adult population

The validity of bioelectrical impedance analysis (BIA) for body composition analysis is limited by assumptions relating to body shape. Improvement in BIA technology could overcome these limitations and reduce the population specificity of the BIA algorithm. BIA equations for the prediction of fat-free mass (FFM), total body water (TBW) and extracellular water (ECW) were generated from data obtained on 124 Caucasians (body mass index 18.5-35 kg/m(2)) using a four-compartment model and dilution techniques as references. The algorithms were validated in an independent multiethnic population (n=130). The validity of BIA results was compared (i) between ethnic groups and (ii) with results from the four-compartment model and two-compartment methods (air-displacement plethysmography, dual-energy X-ray absorptiometry and deuterium dilution). Indices were developed from segmental R and Xc values to represent the relative contribution of trunk and limbs to total body conductivity. The coefficient of determination for all prediction equations was high (R(2): 0.94 for ECW, 0.98 for FFM and 0.98 for TBW) and root mean square error was low (1.9 kg for FFM, 0.8 l for ECW and 1.3 kg for TBW). The bias between BIA results and different reference methods was not statistically different between Afro-American, Hispanic, Asian or Caucasian populations and showed a similar difference (-0.2-0.2 kg FFM) when compared with the bias between different two-compartment reference methods (-0.2-0.3 kg FFM). An eight-electrode, segmental multifrequency BIA is a valid tool to estimate body composition in healthy euvolemic adults compared with the validity and precision of other two-compartment reference methods. Population specificity is of minor importance when compared with discrepancies between different reference methods.

Body composition in athletes and sports nutrition: an examination of the bioimpedance analysis technique

The purpose of the current review was to evaluate how body composition can be utilised in athletes, paying particular attention to the bioelectrical impedance analysis (BIA) technique. Various body composition methods are discussed, as well as the unique characteristics of athletes that can lead to large errors when predicting fat mass (FM) and fat-free mass (FFM). Basic principles of BIA are discussed, and past uses of the BIA technique in athletes are explored. Single-prediction validation studies and studies tracking changes in FM and FFM are discussed with applications for athletes. Although extensive research in the area of BIA and athletes has been conducted, there remains a large gap in the literature pertaining to a single generalised athlete equation developed using a multiple-compartment model that includes total body water (TBW). Until a generalised athlete-specific BIA equation developed from a multiple-compartment is published, it is recommended that generalised equations such as those published by Lukaski and Bolonchuk and Lohman be used in athletes. However, BIA equations developed for specific athletes may also produce acceptable values and are still acceptable for use until more research is conducted. The use of a valid BIA equation/device should produce values similar to those of hydrostatic weighing and dual-energy X-ray absorptiometry. However, researchers and practitioners need to understand the individual variability associated with BIA estimations for both single assessments and repeated measurements. Although the BIA method shows promise for estimating body composition in athletes, future research should focus on the development of general athlete-specific equations using a TBW-based three- or four-compartment model.

Is a single bioelectrical impedance equation valid for children of wide ranges of age, pubertal status and nutritional status? Evidence from the 4-component model

Bioelectrical impedance analysis (BIA) is widely used to predict body composition in paediatric research and clinical practice. Many equations have been published, but provide inconsistent predictions. To test whether a single equation for lean mass (LM) estimation from BIA is appropriate across wide ranges of age, pubertal status and nutritional status, by testing whether specific groups differ in the slope or intercept of the equation. In 547 healthy individuals aged 4-24 years (240 males), we collected data on body mass (BM) and height (HT), and lean mass (LM) using the 4-component model. Impedance (Z) was measured using TANITA BC418MA instrumentation. LM was regressed on HT(2)/Z. Multiple regression analysis was conducted to investigate whether groups based on gender, age, pubertal status or nutritional status differed in the association of LM with HT(2)/Z. BM ranged from 5 to 128 kg. HT(2)/Z was a strong predictor of LM (r (2)=0.953, s.e.e.=2.9 kg). There was little evidence of a sex difference in this relationship, however, children aged 4-7 years and 16-19 years differed significantly from other age groups in regression slopes and intercepts. Similar variability was encountered for pubertal stage, but not for nutritional status. No single BIA equation applies across the age range 4-24 years. At certain ages or pubertal stages, the slope and intercept of the equation relating LM to HT(2)/Z alters. Failure to address such age effects is likely to result in poor accuracy of BIA (errors of several kg) for longitudinal studies of change in body composition.

Estimation of bone mineral content from bioelectrical impedance analysis in Indian adults aged 23–81 years: a comparison with dual energy X-ray absorptiometry

The purpose of this study was to validate a Bioelectrical Impedance Analysis (BIA) equation for prediction of Bone Mineral Content (BMC) against Dual energy X-ray Absorptiometry (DXA) in Indian adults. Healthy 113 subjects were investigated by two methods: BMC was measured by DXA and bioelectrical impedance at various frequencies was measured by a commercial segmental multi-frequency BIA instrument. Body parameters were derived from impedance data and a new BIA equation was developed for the estimation of BMC, which exhibited high correlation and low prediction error. It was found valid in subjects with large variations in Body Mass (BM) and age.

Analysis of Body Composition Methods in a Community Sample of African American Women

The purposes of the authors in this study were: (1) to determine whether published body mass index and bioelectrical impedance analysis equations agreed with dual energy x-ray absorptiometry body fat percentage measures and (2) to estimate new body mass index and bioelectrical impedance analysis equations in a sample of African American women. Linear regression was used to determine how well 10 body mass index and bioelectrical impedance analysis equations reflected dual energy x-ray absorptiometry body fat percentage measures in this sample of 74 African American women; new body mass index and bioelectrical impedance analysis equations were created using dual energy x-ray absorptiometry body fat percentage measures as the dependent variable. Participants (M = 47.6 years, SD = 7.7) were classified as overweight or obese (BMI Mean BF% = 35.4, SD = 8.2; BIA Mean BF% = 43.3, SD = 6.9; DXA Mean BF% = 41.5, SD = 6.1). R2 and SEE values indicated that all body mass index and bioelectrical impedance analysis equations were a poorer fit with less precision, and the new bioelectrical impedance analysis equation discussed in this article was a better fit and was more precise. All 10 body mass index and bioelectrical analysis equations inaccurately estimated dual energy x-ray absorptiometry body fat percentage measures in our sample. The new body mass index equation discussed in this article had less estimation bias and more precision than the published body mass index equations and may be a more accurate equation in African American women.

Validation of bioelectrical impedance analysis for total body water assessment against the deuterium dilution technique in Asian children

To develop and cross-validate bioelectrical impedance analysis (BIA) prediction equations of total body water (TBW) and fat-free mass (FFM) for Asian pre-pubertal children from China, Lebanon, Malaysia, Philippines and Thailand. Height, weight, age, gender, resistance and reactance measured by BIA were collected from 948 Asian children (492 boys and 456 girls) aged 8-10 years from the five countries. The deuterium dilution technique was used as the criterion method for the estimation of TBW and FFM. The BIA equations were developed using stepwise multiple regression analysis and cross-validated using the Bland-Altman approach. The BIA prediction equation for the estimation of TBW was as follows: TBW=0.231 × height(2)/resistance+0.066 × height+0.188 × weight+0.128 × age+0.500 × sex-0.316 × Thais-4.574 (R (2)=88.0%, root mean square error (RMSE)=1.3 kg), and for the estimation of FFM was as follows: FFM=0.299 × height(2)/resistance+0.086 × height+0.245 × weight+0.260 × age+0.901 × sex-0.415 × ethnicity (Thai ethnicity =1, others = 0)-6.952 (R (2)=88.3%, RMSE=1.7 kg). No significant difference between measured and predicted values for the whole cross-validation sample was found. However, the prediction equation for estimation of TBW/FFM tended to overestimate TBW/FFM at lower levels whereas underestimate at higher levels of TBW/FFM. Accuracy of the general equation for TBW and FFM was also valid at each body mass index category. Ethnicity influences the relationship between BIA and body composition in Asian pre-pubertal children. The newly developed BIA prediction equations are valid for use in Asian pre-pubertal children.