Assessment of body composition in 8-11 year old children by bioelectrical impedance

In 64 prepubescent schoolchildren, 33 boys and 31 girls, aged 8-11 years, body composition was measured by means of anthropometry, densitometry and bioelectrical impedance. From body density the body fat percentage was calculated using age-specific density values for the fat-free mass. Boys and girls younger than 10 years did not differ in body composition. Older boys however had higher body weights, higher body densities and lower body impedance values. Fat-free mass as determined by densitometry could be predicted by body impedance and body weight with a prediction error of 1.31 kg. The prediction formula was sex-specific. Omitting the impedance in the prediction equation resulted in a 7 per cent lower explained variance and an only slightly higher prediction error of the FFM of 1.65 kg. The prediction formulas from the literature, developed in adult populations, grossly overestimated the fat-free mass in children, probably due to a different water distribution between the intra- and extra-cellular spaces.     

Evaluation of partial body composition using bioelectrical impedance in Japanese children

To clarify the growth pattern of body composition by body part for the management of childhood obesity, we measured body fat and muscle using BIA (bioelectrical impedance analysis) in 685 Japanese elementary schoolchildren (aged 6-11 years). The growth patterns of percentage body fat (%BF), fat mass (FM), and muscle mass (MM) were examined throughout the whole body and in various body parts. The %BF of the whole body was greater in females than in males, and this difference widened with age. The %BF, FM, and MM in each body part showed similar growth patterns and gender differences to those of the whole body. The mean %BF of the left limbs was higher than that of the right limbs at all age groups. BMI was strongly correlated with %BF in both sexes. In conclusion, the compositions of all body parts change similarly with age, and gender differences are also similar in childhood. The effect of one's dominant arm on body composition is seen at a young age. The accumulation of body composition data according to body part is indispensable for understanding childhood body composition and managing obesity.     

The Stayhealthy bioelectrical impedance analyzer predicts body fat in children and adults

Bioelectrical impedance analysis (BIA) is a time-efficient and cost-effective method for estimating body composition. We hypothesized that there would be no significant difference between the Stayhealthy BC1 BIA and the selected reference methods when determining body composition. Thus, the purpose of the present study was to determine the validity of estimating percent body fat (%BF) using the Stayhealthy BIA with its most recently updated algorithms compared to the reference methods of dual-energy x-ray absorptiometry for adults and hydrostatic weighing for children. We measured %BF in 245 adults aged 18 to 80 years and 115 children aged 10 to 17 years. Body fat by BIA was determined using a single 50 kHz frequency handheld impedance device and proprietary software. Agreement between BIA and reference methods was assessed by Bland and Altman plots. Bland and Altman analysis for men, women, and children revealed good agreement between the reference methods and BIA. There was no significant difference by t tests between mean %BF by BIA for men, women, or children when compared to the respective reference method. Significant correlation values between BIA, and reference methods for all men, women, and children were 0.85, 0.88, and 0.79, respectively. Reliability (test-retest) was assessed by intraclass correlation coefficient and coefficient of variation. Intraclass correlation coefficient values were greater than 0.99 (P < .001) for men, women, and children with coefficient of variation values 3.3%, 1.8%, and 1.7%, respectively. The Stayhealthy BIA device demonstrated good agreement between reference methods using Bland and Altman analyses.     

Estimation of body composition by bioelectrical impedance in cancer patients

Measurement of body composition is important in the assessment of nutritional status in cancer patients. The purpose of this study was to validate the bioelectrical impedance (BI) method for body composition estimation in 33 elderly cancer patients (mean age 66 +/- 9 years) using the deuterium dilution technique (2H2O) as the reference method. Height2/Resistance (H2/R) correlated significantly with total body water (TBW) computed from 2H2O (r = 0.89, P less than 0.001; s.e.e. = 2.4 l). The prediction equation for TBW improved significantly (P less than 0.001) by addition of H2/R to the predictor variables weight, height, age and sex. We conclude that BI is a useful measure for the assessment of body composition in cancer patients.     

Assessment of body composition by bioelectrical impedance in a population aged greater than 60 y

Body composition was measured in a group of 35 healthy men and 37 healthy women aged 60-83 y. Body mass index (BMI) in men was 25.0 +/- 2.2 kg/m2 (means +/- SD) and in women, 25.9 +/- 3.2 kg/m2. BMI was low in relation to body fat percentage as determined by skinfold-thickness measurements or densitometry in comparison with the relation found in younger adults. Mean body fat percentage of the male subjects (aged 70.4 +/- 5.2 y) as determined by densitometry was 31.0 +/- 4.5%, whereas in women (aged 68.0 +/- 5.2 y) it was 43.9 +/- 4.3%. Body impedance correlated with fat-free mass (FFM). The best prediction formulas for the FFM from body impedance and anthropometric variables were 1) FFM (kg) = (0.671 x 10(4) x H2/R) + 3.1S + 3.9 where H is body height (m), R is resistance (omega), and S is gender (females, 0; males, 1) (r = 0.94; SEE = 3.1 kg) and 2) FFM (kg) = (0.360 x 10(4) x H2/R) + 0.359BW + 4.5S - 20T + 7.0 where BW is body weight (kg) and T is thigh circumference (m) (r = 0.96; SEE = 2.5 kg). The prediction equations from the literature, generally determined in younger populations, overestimated FFM in elderly subjects by approximately 6 kg and are not applicable to elderly subjects.     

Assessment of body composition by bioelectrical impedance analysis without the need for measurement of height

Conventional whole-body single frequency bioelectrical impedance analysis (BIA) of body composition typically uses height as a surrogate measure of conductor length. A new method of BIA analysis for the prediction of body cell mass (BCM) and extracellular water (ECW, as % body weight) not using height has been introduced-the Soft Tissue Analyser (STA(TM), Akern Sri, Florence, Italy)-making it ideal for use in subjects where measurement of height is difficult or impossible. The performance of the new analytical method in predicting BCM and ECW in 139 normal control subjects was assessed by comparison with reference data obtained from a four-component (4-C) model of body composition and with predictions obtained from conventional BIA analysis. Both predicted BCM and ECW were strongly (r=0.82, SEE=6.3 kg and 0.89, SEE=1.3 kg respectively) correlated with the corresponding 4-C model measurements although differing significantly from the lines of identity (P<0.0001). Fat-free mass, calculated from STA estimates of BCM and ECW, was better predicted (r=0.91, SEE=5.6 kg). The significant differences in STA-group mean values for BCM and ECW and wide limits of agreement compared with the reference data indicate that the method cannot be used with confidence for prediction of these body compartments despite the obvious advantage of not requiring an accurate measurement of height.     

Assessment of body fluid compartment volumes by multifrequency bioelectrical impedance spectroscopy in children with dengue

Dengue haemorrhagic fever (DHF), the most severe form of illness following infection with a dengue virus, is characterized by plasma leakage and a period of increased microvascular permeability. Monitoring of plasma volume and body fluid compartment shifts is an integral part of the clinical management of DHF, and is crucial to the performance of clinical research studies on DHF pathogenesis. Multifrequency bioelectrical impedance spectroscopy (BIS) was assessed as a non-invasive method to monitor body fluid compartment shifts in children participating in a prospective, hospital-based, study of dengue virus infections in Thailand. Over the 48 h surrounding defervescence, the extracellular water/intracellular water ratio (ECW/ICW) rose in children with dengue virus infections and correlated with increasing disease severity [DHF > intermediate dengue fever (DF)/DHF > DF]. Plasma leakage remained within the ECW compartment and was not directly measured by multifrequency BIS. Expansion of the ECW space in DHF appeared to be primarily due to diminished renal water clearance. During the course of dengue illness, multifrequency BIS did not improve on serial haematocrit and bodyweight determinations for monitoring plasma volume contraction and ECW expansion, respectively.     

External cross-validation of bioelectrical impedance analysis for the assessment of body composition in Korean adults

Bioelectrical impedance analysis (BIA) models must be validated against a reference method in a representative population sample before they can be accepted as accurate and applicable. The purpose of this study was to compare the eight-electrode BIA method with DEXA as a reference method in the assessment of body composition in Korean adults and to investigate the predictive accuracy and applicability of the eight-electrode BIA model. A total of 174 apparently healthy adults participated. The study was designed as a cross-sectional study. FM, %fat, and FFM were estimated by an eight-electrode BIA model and were measured by DEXA. Correlations between BIA_%fat and DEXA_%fat were 0.956 for men and 0.960 for women with a total error of 2.1%fat in men and 2.3%fat in women. The mean difference between BIA_%fat and DEXA_%fat was small but significant (P < 0.05), which resulted in an overestimation of 1.2 ± 2.2%fat (95% CI: -3.2-6.2%fat) in men and an underestimation of -2.0 ± 2.4%fat (95% CI: -2.3-7.1%fat) in women. In the Bland-Altman analysis, the %fat of 86.3% of men was accurately estimated and the %fat of 66.0% of women was accurately estimated to within 3.5%fat. The BIA had good agreement for prediction of %fat in Korean adults. However, the eight-electrode BIA had small, but systemic, errors of %fat in the predictive accuracy for individual estimation. The total errors led to an overestimation of %fat in lean men and an underestimation of %fat in obese women.     

Validation of body composition determination by bioelectrical impedance analysis in acromegaly.

Body composition determination by bioelectrical impedance analysis (BIA) has been compared with measurement of total body water (TBW) by tritiated water dilution and estimation of body fat (BF) by measurement of TBW and total body potassium (TBK) in a four-compartment model, in patients with acromegaly. This disorder is accompanied by a profound aberration in body composition. Furthermore TBW and BF were predicted on the basis of anthropometric variables alone. Paired comparisons of TBW estimations by isotope dilution and BIA showed good correlation (Spearman's rank correlation 0.95, P less than 0.01). Isotope dilution resulted in a mean of 1.7 liter (standard deviation 1.87) higher values. Comparison of BF estimations showed also a significant correlation (Spearman's rank correlation 0.75, P less than 0.01), with slightly higher values for BIA (mean 1.4 kg; standard deviation 2.99). BIA improved the prediction of TBW and BF compared with predictions based on anthropometric variables. In a population of acromegalic patients, BIA seemed to be a useful method to estimate TBW and BF.     

A longitudinal comparison of body composition by total body water and bioelectrical impedance in adolescent girls

Previous studies have assessed the ability of bioelectrical impedance analysis (BIA) to estimate body composition cross-sectionally, but less is known about the ability of BIA to detect changes in body composition longitudinally over the adolescent growth period. Body composition was assessed by isotopic dilution of H(2)(18)O and BIA in 196 initially nonobese girls enrolled in a longitudinal study. Two prediction equations for use in our population of girls were developed, one for use premenarcheally and one for use postmenarcheally. We compared estimates from our equation with those derived from several published equations. Using longitudinal data analysis techniques, we estimated changes in fat-free mass (FFM) and percentage body fat (%BF) over time from BIA, compared with changes in FFM and % BF estimated by H(2)(18)O. A total of 422 measurements from 196 girls were available for analysis. Of the participants, 26% had one measurement of body composition, 43% had two measurements of body composition and 31% had three or more measurements of body composition. By either H(2)(18)O or BIA, the mean %BF at study entry was 23% (n = 196) and the mean %BF at 4 y postmenarche was 27% (n = 133). In our cohort, the best predictive equations to estimate FFM by BIA were: PREMENARCHE: FFM = -5.508 + (0.420 x height(2)/resistance) + (0.209 x weight) + (0.08593 x height) + (0.515 x black race) - (0.02273 x other race). POSTMENARCHE: FFM = -11.937 + (0.389 x height(2)/resistance) + (0.285 x weight) + (0.124 x height) + (0.543 x black race) + (0.393 x other race). Overall, we found that BIA provided accurate estimates of the change in both FFM and %BF over time.     

Assessment of intracellular water by whole body bioelectrical impedance and total body potassium in HIV-positive patients

OBJECTIVE: Bioelectrical impedance analysis (BIA) is widely used as bedside assessment of body composition. Body cell mass (BCM) and intracellular water (ICW) are clinically important body compartments. Estimates of ICW obtained from BIA by different calculation approaches were compared to a reference method in male HIV-infected patients. PATIENTS: Representative subsample of clinically stable HIV-infected outpatients, consisting of 42 men with a body mass index of 22.4 +/- 3.8 kg/m(2)(range, 13-l31 kg/m(2)). METHODS: Total body potassium was assessed in a whole body counter, and compared to 50 kHz monofrequency BIA and multifrequency bioelectrical impedance spectroscopy. Six different prediction equations for ICW from BIA data were applied. Methods were compared by the Bland-Altman method. RESULTS: BIA-derived ICW estimates explained 58% to 73% of the observed variance in ICW (TBK), but limits of confidence were wide (-16.6 to +18.2% for the best method). BIA overestimated low ICW (TBK) and underestimated high ICW (TBK) when normalized for weight or height. Mono- and multifrequency BIA were not different in precision but population-specific equations tended to narrower confidence limits. CONCLUSION: BIA is an unreliable method to estimate ICW in this population, in contrast to the better established estimation of total body water and extracellular water. Potassium depletion in severe malnutrition may contribute to this finding but a major part of the residual between methods remains unexplained.     

Comparisons of body composition derived from anthropometric and bioelectrical impedance methods

This study compared bioelectrical impedance analysis (BIA) measurements with current bedside techniques for determination of body composition in 18 normal volunteers to evaluate the relative usefulness of these methods as adjuncts to assessment in surgical nutrition. Anthropometrics (weight, height, and two skinfold thicknesses) and age and sex were used to derive body density (D) or total body water (TBW) by two methods. Method 1: D was calculated from the logarithm of skinfold thickness according to Durnin and Womersley, adapted for age and sex. Method 2: TBW was calculated from height, weight, and sex according to Hume and Weyers. Resistance and reactance were measured with a four terminal impedance plethysmograph; from these data plus height, weight, and sex, lean body mass (LBM) was derived. In each instance, Siri's and Pace and Rathburn's equations were used to derive the remaining parameters of body composition: D, total body fat (TBF), TBW, and LBM. Using the paired t-test, no statistically significant differences were seen in any parameter determined by the different methods. These results show that D, TBW, TBF, and LBM in a population of healthy individuals under steady-state conditions can be estimated by anthropometric-derived formulas with the same relative accuracy as that provided from estimates based upon BIA measurements.