New equations for estimating body cell mass from bioimpedance parallel models in healthy older Germans

Comparison of series and parallel reactance to identify changes in intracellular water in response to physical training in athletes during a sports season

OBJECTIVE

Cross-sectional evidence has demonstrated that parallel reactance obtained by bioelectrical impedance analysis (BIA) may be an alternative to the regularly used series of measurements to predict intracellular water (ICW) in athletes. However, we are not aware of any studies that have determined the predictive role or compared the effectiveness of both series and parallel reactance for tracking ICW changes during an athletic season. The main aim of this study was to determine the predictive role and compare both series and parallel reactance (Xc) in tracking ICW during an athletic season.

RESEARCH METHODS AND PROCEDURES

This longitudinal study analyzed 108 athletes in the preparatory and competitive periods. Using dilution techniques, total body water (TBW) and extracellular water (ECW) were determined and ICW was calculated. Resistance (R), Xc, and impedance (Z) standardized for height were obtained through BIA spectroscopy using a frequency of 50kHz in a series array and then mathematically transformed in a parallel array.

RESULTS

Multiple regression analyses showed that only changes in parallel Xc and capacitance (CAP) (P < 0.05) were predictors of delta ICW during the sports season. In contracts, this was not the case for Xcs. Both changes in R and Z, series and parallel, predicted similarly the changes in ECW and TBW (P < 0.05) in athletes.

CONCLUSION

Our findings highlight the potential of parallel BIA values to detect changes in body water compartments over a competitive season. These data provide preliminary evidence that changes in parallel Xc/H, and ultimately CAP, represent valid markers of alterations in cell volume during a sports season.

High-standard predictive equations for estimating body composition using bioelectrical impedance analysis: a systematic review

The appropriate use of predictive equations in estimating body composition through bioelectrical impedance analysis (BIA) depends on the device used and the subject's age, geographical ancestry, healthy status, physical activity level and sex. However, the presence of many isolated predictive equations in the literature makes the correct choice challenging, since the user may not distinguish its appropriateness. Therefore, the present systematic review aimed to classify each predictive equation in accordance with the independent parameters used. Sixty-four studies published between 1988 and 2023 were identified through a systematic search of international electronic databases. We included studies providing predictive equations derived from criterion methods, such as multi-compartment models for fat, fat-free and lean soft mass, dilution techniques for total-body water and extracellular water, total-body potassium for body cell mass, and magnetic resonance imaging or computerized tomography for skeletal muscle mass. The studies were excluded if non-criterion methods were employed or if the developed predictive equations involved mixed populations without specific codes or variables in the regression model. A total of 106 predictive equations were retrieved; 86 predictive equations were based on foot-to-hand and 20 on segmental technology, with no equations used the hand-to-hand and leg-to-leg. Classifying the subject's characteristics, 19 were for underaged, 26 for adults, 19 for athletes, 26 for elderly and 16 for individuals with diseases, encompassing both sexes. Practitioners now have an updated list of predictive equations for assessing body composition using BIA. Researchers are encouraged to generate novel predictive equations for scenarios not covered by the current literature.Registration code in PROSPERO: CRD42023467894.

Prediction of body water compartments by raw bioelectrical impedance parameters in athletes: Comparison between series and parallel measurements

BACKGROUND

The aim of this study was to determine the predictive role of series and parallel bioelectrical impedance-derived parameters in predicting total body (TBW), intracellular (ICW), and extracellular water (ECW) in athletes.

METHODS

This cross-sectional study analyzed 134 male (21.33 ± 5.11 years) and 64 female (20.45 ± 5.46 years) athletes. Using dilution techniques, TBW and ECW were determined while ICW was the difference between both. Raw and standardized for height (/H) bioelectrical resistance (R), reactance (Xc), and impedance (Z) values were obtained using a phase-sensitive device at a single frequency in a series array (s). These were mathematically transformed in a parallel array (p) and capacitance (CAP). Fat-free mass (FFM) was assessed by dual-energy X-ray absorptiometry.

RESULTS

Multiple regressions adjusted for age and FFM show that R/Hs, Z/Hs, R/Hp, and Z/Hp were significant predictors of TBW (p < 0.001 in females and males). While Xc/Hs did not predict ICW, Xc/Hp was a predictor (p < 0.001 in females and Males). In females, R/H and Z/H predicted similarly TBW, ICW, and ECW. In males, R/Hs was considered a better predictor than R/Hp for TBW and ICW, and the Xc/Hp was considered the best predictor for ICW. Another significant predictor of ICW was CAP (p < 0.001 in females and males).

CONCLUSION

This study highlights the potential value of parallel bioelectrical impedance values to identify fluid compartments in athletes as an alternative to the regularly used series measurements. Moreover, this study supports Xc in parallel, and ultimately CAP, as valid indicators of cell volume.

Phase angle in localized bioimpedance measurements to assess and monitor muscle injury

Localized bioimpedance (L-BIA) measurements are an innovative method to non-invasively identify structural derangement of soft tissues, principally muscles, and fluid accumulation in response to traumatic injury. This review provides unique L-BIA data demonstrating significant relative differences between injured and contralateral non-injured regions of interest (ROI) associated with soft tissue injury. One key finding is the specific and sensitive role of reactance (Xc), measured at 50 kHz with a phase-sensitive BI instrument, to identify objective degrees of muscle injury, localized structural damage and fluid accretion, determined using magnetic resonance imaging. The predominant effect of Xc as an indicator of severity of muscle injury is highlighted in phase angle (PhA) measurements. Novel experimental models utilizing cooking-induced cell disruption, saline injection into meat specimens, and measurements of changing amounts of cells in a constant volume provide empirical evidence of the physiological correlates of series Xc as cells in water. Findings of strong associations of capacitance, computed from parallel Xc (X_CP), with whole body counting of 40-potassium and resting metabolic rate support the hypothesis that parallel Xc is a biomarker of body cell mass. These observations provide a theoretical and practical basis for a significant role of Xc, and hence PhA, to identify objectively graded muscle injury and to reliably monitor progress of treatment and return of muscle function.

Higher Body Fat but Similar Phase Angle Values in Patients with the Classical Form of Congenital Adrenal Hyperplasia in Comparison to a Control Group

This study aimed to compare phase angle (PhA) and bioelectrical impedance vector analysis (BIVA) values between adult patients with congenital adrenal hyperplasia caused by 21-hydroxylase deficiency (CAH21OHD) and a control group. A total of 22 patients (15 women, 22.9 ± 3.7 years) were compared with 17 controls (11 women, 27.0 ± 2.5 years). Body composition was determined by dual-energy X-ray absorptiometry. Bioelectrical impedance was used to calculate PhA, and BIVA was performed using specific software. Student’s t-test and analysis of covariance were used to compare groups. Hedges’ G and partial n2 were calculated for the effect estimates. Hotelling’s t2 test was used to compare the mean impedance vectors between the groups. The Mahalanobis test was used to determine the distance between confidence ellipses. Patients with CAH21OHD had a higher fat mass percentage than that of the control group (both sexes). There was no significant difference in PhA values between groups (CAH21OHD vs. control) in females (6.9° vs. 6.3°, p = 0.092) and males (8.2° vs. 8.1°, p = 0.849), after adjusting for covariates (age and height). BIVA analysis showed a significant difference in the mean impedance vectors between the female groups (T2 = 15.9, D = 1.58, p = 0.003) owing to the higher reactance/height (Δ = 8.5; p < 0.001) of the patients. The PhA did not significantly differ between the groups. Female patients had significantly higher reactance values. However, further studies are needed to determine the usefulness of bioimpedance parameters in evaluating the hydration status and cellular integrity of patients with CAH21OHD.

Phase angle as an index of physiological status: validating bioelectrical assessments of hydration and cell mass in health and disease

Bioelectrical impedance (BI) is a practical method to assess body composition in health and disease. This method relies on the passive conduction of an applied, safe, low-level alternating current through water and electrolytes in the body. Using a phase-sensitive device, BI yields measurements of impedance (Z) and its components, resistance (R) and reactance (Xc), that are related geometrically as phase angle (PhA). In vitro studies provide empirical evidence relating BI measurements to physiological variables. Cooking raw food samples results in greater decreases in PhA, predominantly Xc, with smaller reductions R indicating destruction of cell membrane integrity with simultaneous movement of fluid from intracellular to extracellular space. Infusion of saline into a cell-free model shows a proportional decrease in R with increases in volume. Saline infusion in a composite model of cells disproportionately decreases Xc and PhA, compared to R, demonstrating greater relative expansion of extracellular water (ECW) with a lesser relative increase in total fluid volume. Surgical patients treated with fluid infusion and diuresis demonstrate changes in Xc predominantly indicating relative changes in ECW with lesser variations in R indicating fluctuations in total fluid volume. Proteomics studies disclose strong independent associations of PhA with protein markers of fluid overload and protein proliferation. Interpretations of PhA measurements for body cell mass should be examined in the context of hydration status.

Body Composition Results of Caucasian Young Normal Body Mass Women in the Follicular Proliferative Phase, Measured for the Different Positions of Limbs

The bioelectrical impedance analysis (BIA) became a standardized technique for assessing body composition, but many factors affect the reproducibility of measurement, including body and limbs position. In spite of the fact that it is recommended for patient to be in a supine position, with arms abducted at least 30° and legs abducted at approximately 45°, a lot of authors conduct their measurements with arms and legs of patients separated to not touch the body but not strictly following the recommendations. Taking this into account, the aim of the study was to analyze the body composition results of Caucasian young normal body mass women in the follicular proliferative phase, measured for the different positions of limbs in order to compare the results obtained in the recommended position (with arms abducted at least 30° and legs abducted at approximately 45°) and in the commonly used position (not following strictly the recommendations). The study was conducted in a homogenous group of 100 adult females under the age of 30 years using BIA 101/ASE with the Bodygram Pro software and its equations by Akern Srl, Firenze, Italy, based on the measurement recommendations. The measurements were conducted (1) in a recommended position of arms abducted at least 30° and legs abducted at approximately 45° and (2) with arms spread and legs separated to not touch the body to compare the body composition assessment (fat mass, fat-free mass, body cell mass, muscle mass, water content, extracellular water content, and intracellular water content). It was stated that the results obtained for various positions of limbs were positively correlated (p < 0.0001; R > 0.5). At the same time, the statistically significant differences dependent on the position were observed for the calculated results of body cell mass (lower results for the recommended position for the results observed in kg and % of body mass; p = 0.0165 and p = 0.0075, respectively) and muscle mass (lower results for the recommended position for the results observed in kg and % of body mass; p = 0.0025 and p = 0.0011, respectively), as well as extracellular and intracellular water (higher % of total body water for the extracellular water and lower for intracellular water; p = 0.0049 and p = 0.0115, respectively), resulting from the measured resistance and reactance values. For all listed comparisons of significantly differing variables, weighted κ statistics indicated moderate agreement (values of 0.41–0.60), and the Bland–Altman plot analysis indicated no agreement (Bland–Altman index of >5%). While compared with the reference values, the major differences were observed for extracellular/intracellular water content, as, while applying a method with arms and legs separated to not touch the body (not recommended position), the extracellular water content was underestimated for 31% and intracellular water content was overestimated for 28% of participants. It may be concluded that the recommended body position of arms abducted at least 30° and legs abducted at approximately 45° should be chosen to ensure the reliability of the BIA measurements, as, while the recommendations of a body position are not followed, the results obtained may be misleading and may not reflect the actual body composition.

Exploring the potential role of phase angle as a marker of oxidative stress: A narrative review

Chronic conditions including non-communicable diseases have become increasingly prevalent in the past decade. Proinflammatory cytokines are associated with the development of several pathologies, their prognoses, and their associated mortality. Chronic inflammation is also associated with oxidative stress whereby reactive oxygen species (ROS) induce cellular injury and, thus, by doing so, initiate inflammatory signaling. Phase angle (PhA) is a measurable body composition parameter obtained using bioelectrical impedance analysis (BIA). PhA is considered an indicator of cellular health and integrity and is also related to inflammatory markers and inflammation. Given the association among oxidative stress, cell damage, and inflammation that may in turn be associated with low PhA values, it is expected that PhA could mirror oxidative stress. In this hypothesis-generating, narrative review we summarize the current knowledge regarding the potential relationship between PhA and oxidative stress and their interrelationship in chronic conditions.

Segmental Phase Angle and Body Composition Fluctuation of Elite Ski Jumpers between Summer and Winter FIS Competitions

(1) Background: The purpose of this study was to observe segmental phase angle (PhA) and body composition fluctuation of elite ski jumpers. (2) Methods: In the study, 12 professional ski jumpers took part. Body composition was estimated with segmental multi-frequency bioelectrical impedance analysis. Repeated ANOVA was used to check the parameters' variability in time. The symmetry between the right and left side of the body was verified with the t-test for dependent samples. Pearson's linear correlation coefficient was calculated. (3) Results: The most stable parameter was body weight. An increase in the visceral fat area was noted, the fat-free mass dropped, and significant changes were noted in the internal and external cell water parameters. Parameters connected with water between the right and left side of the body were symmetrical. Significant correlation between PhA values and body parameters with regard to fat tissue and PhA values of the legs was noticed when PhA was measured at 50 kHz. (4) Conclusions: PhA could be considered as a ski jumper body symmetry monitoring tool. The described relationship may be useful for the assessment of body fat change, which, in the case of jumpers, is crucial. Moreover, our data suggest that segmental PhA evaluation could be a good solution for ski jumpers as a confirmation if lowered body mass and low BMI are still healthy and increase the chance for longer jumps and good performance.

Bioimpedance analysis with a novel predictive equation - A reliable technique to estimate fat free mass in birth weight based cohorts of Asian Indian males

AIM

To validate bioimpedance based predictive equations for fat free mass (FFM) against DEXA and to derive a novel birth weight based predictive equation for FFM in a birth weight based cohort of healthy Asian Indian men.

METHODOLOGY

Whole body composition was done using DEXA and bioimpedance in 117 young Asian Indian men, born of normal birth weight (n = 59, birth weight ≥2.5 kg) or low birth weight (n = 58, birth weight < 2.5 kg). Predictive accuracy of 11 different bioimpedance based equations for FFM was evaluated using Pearson's correlation analysis and the root of mean squared prediction error (RMSE) analysis.

RESULTS

The mean FFM (on DEXA) and total lean mass & impedance index (on bioimpedance) were significantly higher in the low birth weight cohort. Significantly higher body fat percentage was noted on bioimpedance, for the normal birth weight cohort, but not on DEXA. In addition, the mean values of predicted FFM were significantly higher in the low birth weight cohort for 9 different predictive equations. Specifically, the mean FFM values obtained using the predictive equations of Schaefer et al., Hoot cooper et al. and Hughes et al. were in close agreement with the actual FFM values on DEXA. A novel predictive equation (CMC equation) for FFM based on birth weight was derived. FFM = 32.637 + (-0.222*age) + (-32.51*waist-to-hip ratio) + (0.33*body mass index) + (1.58 * 1 or 2 (1 = normal birth weight, 2 = low birth weight) + (0.510*waist circumference).

CONCLUSIONS

Our study findings substantiate the validity of Bio-impedance analysis (BIA) as a reliable and noninvasive tool for estimating body composition measures in birth-weight based cohorts of Asian Indian males. Further, we have devised a novel BIA-based predictive equation that can be useful in larger epidemiological studies to look at alterations in body fat in this cohort.

Pitfalls in the measurement of muscle mass: a need for a reference standard

BACKGROUND

All proposed definitions of sarcopenia include the measurement of muscle mass, but the techniques and threshold values used vary. Indeed, the literature does not establish consensus on the best technique for measuring lean body mass. Thus, the objective measurement of sarcopenia is hampered by limitations intrinsic to assessment tools. The aim of this study was to review the methods to assess muscle mass and to reach consensus on the development of a reference standard.

METHODS

Literature reviews were performed by members of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis working group on frailty and sarcopenia. Face-to-face meetings were organized for the whole group to make amendments and discuss further recommendations.

RESULTS

A wide range of techniques can be used to assess muscle mass. Cost, availability, and ease of use can determine whether the techniques are better suited to clinical practice or are more useful for research. No one technique subserves all requirements but dual energy X-ray absorptiometry could be considered as a reference standard (but not a gold standard) for measuring muscle lean body mass.

CONCLUSIONS

Based on the feasibility, accuracy, safety, and low cost, dual energy X-ray absorptiometry can be considered as the reference standard for measuring muscle mass.

Validation of two portable bioelectrical impedance analyses for the assessment of body composition in school age children

Background

Bioelectrical impedance analysis (BIA) is a convenient and child-friendly method for longitudinal analysis of changes in body composition. However, most validation studies of BIA have been performed on adult Caucasians. The present cross-sectional study investigated the validity of two portable BIA devices, the Inbody 230 (BIA_8MF) and the Tanita BC-418 (BIA_8SF), in healthy Taiwanese children.

Methods

Children aged 7–12 years (72 boys and 78 girls) were recruited. Body composition was measured by the BIA_8SF and the BIA_8MF. Dual X-ray absorptiometry (DXA) was used as the reference method.

Results

There were strong linear correlations in body composition measurements between the BIA_8SF and DXA and between the BIA_8MF and DXA. Both BIAs underestimated fat mass (FM) and percentage body fat (%BF) relative to DXA in both genders The degree of agreement in lean body mass (LBM), FM, and %BF estimates was higher between BIA_8MF and DXA than between BIA_8SF and DXA. The Lin’s concordance correlation coefficient (ρ_c) for LBM_8MF met the criteria of substantial to perfect agreement whereas the ρ_c for FM_8MF met the criteria of fair to substantial agreement. Bland-Altman analysis showed a clinically acceptable agreement between LBM measures by BIA_8MF and DXA. The limit of agreement in %BF estimation by BIA and DXA were wide and the errors were clinically important. For the estimation of ALM, BIA_8SF and BIA_8MF both provided poor accuracy.

Conclusions

For all children, LBM measures were precise and accurate using the BIA_8MF whereas clinically significant errors occurred in FM and %BF estimates. Both BIAs underestimated FM and %BF in children. Thus, the body composition results obtained using the inbuilt equations of the BIA_8SF and BIA_8MF should be interpreted with caution, and high quality validation studies for specific subgroups of children are required prior to field research.

Hand-to-Hand Model for Bioelectrical Impedance Analysis to Estimate Fat Free Mass in a Healthy Population

This study aimed to establish a hand-to-hand (HH) model for bioelectrical impedance analysis (BIA) fat free mass (FFM) estimation by comparing with a standing position hand-to-foot (HF) BIA model and dual energy X-ray absorptiometry (DXA); we also verified the reliability of the newly developed model. A total of 704 healthy Chinese individuals (403 men and 301 women) participated. FFM (FFM_DXA) reference variables were measured using DXA and segmental BIA. Further, regression analysis, Bland–Altman plots, and cross-validation (2/3 participants as the modeling group, 1/3 as the validation group; three turns were repeated for validation grouping) were conducted to compare tests of agreement with FFM_DXA reference variables. In male participants, the hand-to-hand BIA model estimation equation was calculated as follows: FFM^m_HH = 0.537 h²/Z_HH − 0.126 year + 0.217 weight + 18.235 (r² = 0.919, standard estimate of error (SEE) = 2.164 kg, n = 269). The mean validated correlation coefficients and limits of agreement (LOAs) of the Bland–Altman analysis of the calculated values for FFM^m_HH and FFM_DXA were 0.958 and −4.369–4.343 kg, respectively, for hand-to-foot BIA model measurements for men; the FFM (FFM^m_HF) and FFM_DXA were 0.958 and −4.356–4.375 kg, respectively. The hand-to-hand BIA model estimating equation for female participants was FFM^F_HH = 0.615 h²/Z_HH − 0.144 year + 0.132 weight + 16.507 (r² = 0.870, SEE = 1.884 kg, n = 201); the three mean validated correlation coefficient and LOA for the hand-to-foot BIA model measurements for female participants (FFM^F_HH and FFM_DXA) were 0.929 and −3.880–3.886 kg, respectively. The FFM_HF and FFM_DXA were 0.942 and −3.511–3.489 kg, respectively. The results of both hand-to-hand and hand-to-foot BIA models demonstrated similar reliability, and the hand-to-hand BIA models are practical for assessing FFM.

Bioelectrical impedance vector analysis (BIVA) for the assessment of two-compartment body composition

This review is directed to define the efficacy of bioelectrical impedance vector analysis (BIVA) for assessing two-compartment body composition. A systematic literature review using MEDLINE database up to 12 February 2014 was performed. The list of papers citing the first description of BIVA, obtained from SCOPUS, and the reference lists of included studies were also searched. Selection criteria included studies comparing the results of BIVA with those of other techniques, and studies analyzing bioelectrical vectors of obese, athletic, cachectic and lean individuals. Thirty articles met the inclusion criteria. The ability of classic BIVA for assessing two-compartment body composition has been mainly evaluated by means of indirect techniques, such as anthropometry and bioelectrical impedance analysis (BIA). Classic BIVA showed a high agreement with body mass index, that can be interpreted in relation to the greater body mass of obese and athletic individuals, whereas the comparison with BIA showed less consistent results, especially in diseased individuals. When a reference method was used, classic BIVA failed to accurately recognize FM% variations, whereas specific BIVA furnished good results. Specific BIVA is a promising alternative to classic BIVA for assessing two-compartment body composition, with potential application in nutritional, sport and geriatric medicine.

Predição da massa corporal magra de adultos brasileiros através da área muscular do braço

INTRODUÇÃO: A área muscular do braço (Amb) é componente da massa corporal magra (MCM).OBJETIVO: Propor uma equação para estimativa da MCM através da Amb.MÉTODOS: Quarenta e cinco voluntários masculinos, aparentemente saudáveis, com idade média de 22 ± 3 anos e massa corporal 74,9 ± 8,43 kg, foram distribuídos randomicamente em grupos de validação interna (VI) e validação externa (VE). Tais sujeitos foram submetidos a medidas antropométricas e à hidrometria. Antes dos testes, os sujeitos receberam as seguintes orientações: a) evitar o consumo de cafeína e álcool nas 24 horas precedentes; b) não realizar atividade física extenuante (≥ 5 METs), pelo menos nas 12 horas prévias ao exame e; c) período pós-prandial de quatro horas. A área muscular do braço foi determinada através da equação: Ama= [C-(T .π)]²÷(4 .π).RESULTADOS: O modelo derivado para predição foi: MCM= 9,127 + (0,625 . MC) + (0,139 . Amb); r2= 0,91, EPE= 1,85 kg (2,5% da massa corporal ou MC). Para VE, não houve diferença significativa entre a MCM medida pela eletrobioimpedância e a prevista pela fórmula acima (p=0,350), r²= 0,94, CV%= 2,0%, CCI= 0,97 e EPE= 1,87 kg.CONCLUSÃO: A equação de regressão múltipla derivada permite estimar a MCM de jovens brasileiros do sexo masculino.

Extracellular-to-body cell mass ratio and subjective global assessment in head-and-neck cancers

BACKGROUND

The ratio of extracellular mass to body cell mass (ecm/bcm), determined by bioelectrical impedance analysis, has been found to be a potentially useful indicator of nutrition status. Subjective global assessment (sga) is a subjective method of evaluating nutrition status in head-and-neck cancer. The present study was conducted to investigate the association between ecm/bcm and sga in head-and-neck cancer.

METHODS

Patients were classified as either well-nourished or malnourished by sga. Bioelectrical impedance analysis was conducted on a population of 75 patients with histologically confirmed head-and-neck cancer, and the ecm/bcm was calculated. Receiver operating characteristic curves were estimated using the nonparametric method to determine an optimal cut-off value of the ecm/bcm.

RESULTS

Compared with malnourished patients, those who were well-nourished had a statistically significantly lower ecm/bcm (1.11 vs. 1.28, p = 0.005). An ecm/bcm cut-off of 1.194 was 76% sensitive and 63% specific in detecting malnutrition.

CONCLUSIONS

The ecm/bcm can be an indicator that detects malnutrition in patients with head-and-neck cancer. Further observations are needed to validate the significance of the ecm/bcm and to monitor nutrition interventions.

Accuracy of specific BIVA for the assessment of body composition in the United States population

Background

Bioelectrical impedance vector analysis (BIVA) is a technique for the assessment of hydration and nutritional status, used in the clinical practice. Specific BIVA is an analytical variant, recently proposed for the Italian elderly population, that adjusts bioelectrical values for body geometry.

Objective

Evaluating the accuracy of specific BIVA in the adult U.S. population, compared to the ‘classic’ BIVA procedure, using DXA as the reference technique, in order to obtain an interpretative model of body composition.

Design

A cross-sectional sample of 1590 adult individuals (836 men and 754 women, 21–49 years old) derived from the NHANES 2003–2004 was considered. Classic and specific BIVA were applied. The sensitivity and specificity in recognizing individuals below the 5^th and above the 95^th percentiles of percent fat (FM_DXA%) and extracellular/intracellular water (ECW/ICW) ratio were evaluated by receiver operating characteristic (ROC) curves. Classic and specific BIVA results were compared by a probit multiple-regression.

Results

Specific BIVA was significantly more accurate than classic BIVA in evaluating FM_DXA% (ROC areas: 0.84–0.92 and 0.49–0.61 respectively; p = 0.002). The evaluation of ECW/ICW was accurate (ROC areas between 0.83 and 0.96) and similarly performed by the two procedures (p = 0.829). The accuracy of specific BIVA was similar in the two sexes (p = 0.144) and in FM_DXA% and ECW/ICW (p = 0.869).

Conclusions

Specific BIVA showed to be an accurate technique. The tolerance ellipses of specific BIVA can be used for evaluating FM% and ECW/ICW in the U.S. adult population.

The potential of classic and specific bioelectrical impedance vector analysis for the assessment of sarcopenia and sarcopenic obesity

PURPOSE

The aim of this paper is to investigate whether bioelectrical impedance vector analysis (BIVA) can be a suitable technique for the assessment of sarcopenia. We also investigate the potential use of specific BIVA as an indicator of sarcopenic obesity.

SUBJECTS AND METHODS

The sample comprised 207 free-living elderly individuals of both sexes, aged 65 to 93 years. Anthropometric and bioelectrical measurements were taken according to standard criteria. The "classic" and "specific" BIVA procedures, which respectively correct bioelectrical values for body height and body geometry, were used. Dual energy X-ray absorptiometry (DXA) was used as the reference method for identifying sarcopenic and obese sarcopenic individuals. Bioelectrical and DXA values were compared using Student's t-test and Hotelling's T(2) test, as well as Pearson's correlation coefficient.

RESULTS

According to classic BIVA, sarcopenic individuals of both sexes showed higher values of resistance/height (R/H; p < 0.01) and impedance/height (Z/H; p < 0.01), and a lower phase angle (p < 0.01). Similarly, specific BIVA showed significant differences between sarcopenic and nonsarcopenic individuals (men: T(2) = 15.7, p < 0.01; women: T(2) = 10.7, p < 0.01), with the sarcopenic groups showing a lower specific reactance and phase angle. Phase angle was positively correlated with the skeletal muscle mass index (men: r = 0.52, p < 0.01; women: r = 0.31, p < 0.01). Specific BIVA also recognized bioelectrical differences between sarcopenic and sarcopenic obese men (T(2) = 13.4, p < 0.01), mainly due to the higher values of specific R in sarcopenic obese individuals.

CONCLUSION

BIVA detected muscle-mass variations in sarcopenic individuals, and specific BIVA was able to discriminate sarcopenic individuals from sarcopenic obese individuals. These procedures are promising tools for screening for presarcopenia, sarcopenia, and sarcopenic obesity in routine practice.

Bioelectrical impedance with different equations versus deuterium oxide dilution method for the inference of body composition in healthy older persons

BACKGROUND

There is no consensus regarding the accuracy of bioimpedance for the determination of body composition in older persons.

OBJECTIVE

This study aimed to compare the assessment of lean body mass of healthy older volunteers obtained by the deuterium dilution method (reference) with those obtained by two frequently used bioelectrical impedance formulas and one formula specifically developed for a Latin-American population.

DESIGN

A cross-sectional study.

PARTICIPANTS

Twenty one volunteers were studied, 12 women, with mean age 72±6.7 years.

SETTING

Urban community, Ribeirão Preto, Brazil.

MEASUREMENT

Fat free mass was determined, simultaneously, by the deuterium dilution method and bioelectrical impedance; results were compared. In bioelectrical impedance, body composition was calculated by the formulas of Deuremberg, Lukaski and Bolonchuck and Valencia et al.

RESULTS

Lean body mass of the studied volunteers, as determined by bioelectrical impedance was 37.8±9.2 kg by the application of the Lukaski e Bolonchuk formula, 37.4±9.3 kg (Deuremberg) and 43.2±8.9 kg (Valencia et. al.). The results were significantly correlated to those obtained by the deuterium dilution method (41.6±9.3 Kg), with r=0.963, 0.932 and 0.971, respectively. Lean body mass obtained by the Valencia formula was the most accurate.

CONCLUSION

In this study, lean body mass of older persons obtained by the bioelectrical impedance method showed good correlation with the values obtained by the deuterium dilution method. The formula of Valencia et al., developed for a Latin-American population, showed the best accuracy.

The role of fat mass index in determining obesity

OBJECTIVES

The objective of this study is to compare body mass index (BMI), percent body fat (PBF), and fat mass index (FMI) and to investigate the accuracy of FMI as a convenient tool for assessing obesity.

DESIGN

Anthropometric measurements and bioelectrical impedance analyses were performed on 538 Mexican Americans (373 women and 165 men). Correlations between BMI and PBF and between FMI and PBF were investigated. The percentage of persons misclassified as obese using different classifications was calculated. Multiple linear regression analysis was performed to generate predictive models of FMI for males and females separately.

RESULTS

BMI and PBF were correlated in men (rho = 0.877; P < 0.0001) and women (rho = 0.966; P < 0.0001); however, 20 and 67.2% of the men and 9.2 and 84.2% of women, classified as normal weight and overweight by BMI, respectively, were diagnosed as obese by PBF. FMI and PBF were also correlated in men (rho = 0.975; P < 0.0001) and women (rho = 0.992; P < 0.0001). Four percent of the men classified as normal weight and 65.5% classified as overweight by BMI were obese by FMI, while 71.3% of women classified as overweight by BMI were obese by FMI. Misclassification of obesity between FMI and PBF categories was observed in 5.4% of men and 7.8% of women.

CONCLUSIONS

The discrepancy observed between BMI and PBF reflects a limitation of BMI. Conversely, FMI accurately assessed obesity in our study of Mexican Americans, but further studies are necessary to confirm our findings in different ethnic groups.

Bioelectrical impedance analysis and age-related differences of body composition in the elderly

BACKGROUND AND AIM

Significant changes in body composition that have important health related effects may occur in the elderly. In this study, we evaluated the bioelectrical characteristics in a large group of apparently healthy Caucasian men in the age range 50-80 years, as a function of age and body mass index.

METHODS

We studied 315 men with ages ranging from 50 to 80 years. They were divided into three groups according to body mass index (kg/m(2)): 18.5-24.9 normoweight (NW); 25.0-29.9 overweight (OW); > or =30 obese (OB), and they were classified in nine age subgroups: 50-59 (young-old, YO); 60-69 (old, O); 70-80 (oldest, OS). Fat-free mass, fat mass and body cell mass were investigated using conventional bioelectrical impedance analysis. Body composition was also assessed by bioelectrical impedance vector analysis and the RXc graph method.

RESULTS

Body cell mass decreased significantly with age particularly in subgroups of the OW and OB groups (p<0.05). Mean vector displacement followed a definite pattern, with downward migration of the ellipses in the OW and OB groups, after 70 years of age.

CONCLUSIONS

Ageing was associated with a pattern of vector bioelectrical impedance analysis indicating decreased soft tissue mass (fat-free mass and body cell mass), particularly in OW and OB-OS healthy men. We suggest 70 years of age as a cut-off for significant quantitative and qualitative (tissue electrical properties) body composition modifications. This bioelectrical impedance vector analysis pattern associated with ageing and across the different body mass index categories, may be useful for clinical purposes and can be used in geriatric routine to accurately assess the body composition modifications occurring in the elderly.

Estimation of maximal oxygen uptake by bioelectrical impedance analysis

Previous non-exercise models for the prediction of maximal oxygen uptake VO(2max) have failed to accurately discriminate cardiorespiratory fitness within large cohorts. The aim of the present study was to evaluate the feasibility of a completely indirect method for predicting VO(2max) that was based on bioelectrical impedance analysis (BIA) in 66 young, healthy fit men and women. Multiple, stepwise regression analysis was used to determine the usefulness of BIA and additional covariates to estimate VO(2max) (ml min(-1)). BIA was highly correlated to VO(2max) (r = 0.914; P < 0.001) and entered the regression equation first. The inclusion of gender and a physical activity rating further improved the model which accounted for 88% of the variance in VO(2max) and resulted in a relative standard error of the estimate (SEE) of 7.2%. Substantial agreement between the methods was confirmed by the fact that nearly all the differences were within +/-2 SD. Furthermore, in contrast to previously published non-exercise models, no trend of a reduction in prediction accuracy with increasing VO(2max) values was apparent. It was concluded that a non-exercise model based on BIA might be a rapid and useful technique to estimate VO(2max), when a direct test does not seem feasible. However, though the present results are useful to determine the viability of the method, further refinement of the BIA approach and its validation in a large, diverse population is needed before it can be applied to the clinical and epidemiological settings.

Validation of different bioimpedance analyzers for predicting cell mass against whole-body counting of potassium (40K) as a reference method

This study compared two different tetrapolar bioimpedance (BIA) devices for estimating body cell mass (BCM), validated them against whole-body counting of (40)K (TBK method), and developed improved prediction equations for estimating BCM from BIA. In 50 healthy volunteers (age 23-65 years, BMI 18.6-27.7 kg/m(2)), BCM was estimated with the BIA devices Nutriguard-M (Data Input, Germany) and Soft-Tissue-Analyzer-STA (Akern, Italy) and by the TBK method. Methods were compared by the Bland-Altman procedure. New prediction equations for BCM were developed by multiple stepwise regression analysis based on a single BIA parallel model. The Akern device gives similar mean estimates of BCM compared to the Data Input device in males (33.5 vs. 33.3 kg, P = 0.789), but higher values in females (24.6 vs. 22.8 kg; P < 0.001). Both BIA devices overestimate mean BCM relative to the TBK method; in males by 5.0 kg (Data Input, P < 0.001) and 5.1 kg (Akern, P < 0.001); in females by 2.3 kg (Data Input, P < 0.001) and 4.1 kg (Akern, P < 0.001). Limits of agreement between BIA and TBK methods are for males +/-4.99 kg (Data Input) and +/-7.16 kg (Akern); for females, +/-4.69 kg (Data Input) and +/-4.12 kg (Akern). New equations were developed for estimating BCM for both BIA analyzers (Data Input, R(2) = 0.91, SEE = 1.46 kg; Akern, R(2) = 0.90, SEE = 1.48 kg). Since estimates of BCM by the present BIA devices do not differ in males, they might be interchangeable. This does not hold true for females. Because both BIA devices overestimate BCM, the newly developed device-specific equations which reduce bias and limits of agreement should be applied.