A comparison of skinfolds and leg-to-leg bioelectrical impedance for the assessment of body composition in children

BACKGROUND: This field-based investigation examined the congruence between skinfolds and bioelectrical impedance in assessing body composition in children. METHODS: Subjects were 162 female and 160 male children 10-15 years of age. Skinfold measures obtained at the triceps and medial calf and a leg-to-leg bioelectrical impedance system were used to determine percent fat using child-specific equations. Pearson product moment correlations were performed on the percent fat values obtained using skinfolds and bioelectric impedance for the entire data set. Separate correlations were also conducted on gender and age/gender subsets. Dependent t tests were used to compare the two techniques. RESULTS: Percent fat did not differ between skinfolds and bioelectrical impedance for the total subject pool. Bioelectrical impedance overestimated percent fat in girls by 2.6% and underestimated percent fat in boys by 1.7% (p < 0.01). Correlations between skinfolds and bioelectrical impedance ranged from r = 0.51 to r = 0.90. CONCLUSIONS: Leg-to-leg bioelectrical impedance may be a viable alternative field assessment technique that is comparable to skinfolds. The small differences in percent fat between the two techniques may have limited practical significance in school-based health-fitness settings.     

Estimation of body composition from bioelectrical impedance of body segments

This study provides values of anthropometric measurements and specific impedance, for a sample of 104 adults. The hypothesis that the body composition can be estimated more accurately from measurements of lengths and impedance values of the body segments than from the whole body was tested. The impedance of upper and lower extremities (arm and leg) and trunk were used to compute estimates of body composition parameters (FFM, FM, %F, TBW, ECW). The results were compared with those estimated by the impedance of the whole body. These comparisons demonstrated that significative differences resulted from body composition obtained by segmental impedance and by the whole body.     

Body build related body composition and nutrition in adulthood--a comparison of skinfold thickness measurement and bioelectric impedance analysis

The objective of the present study was to conduct a comprehensive analysis of body build, body composition and nutritional status. The study sample consists of 498 men and women aged from 35 to 65 years. Subjects underwent a detailed anthropometric examination incompassing thirty-one body measurements, eleven skinfold thickness measurements, and bioelectrical impedance analysis for determination of body composition. Dietary intake was assessed by a semiquantitative food frequency questionnaire. Body composition was clearly associated with age and body build. Somatometric differentiation by use of the metric index showed that percentage of body fat was significantly higher in pycnomorphic compared to leptomorphic subjects, whereas reported dietary energy intake was lower. Comparison of estimates of body fat showed considerably deviating results for skinfold thickness measurements and bioelectrical impedance analysis depending on the equations used. This was especially pronounced in obese subjects, where, on an average, bioelectrical impedance analysis resulted in higher values for percentage of body fat compared to skinfold thickness measurements. We conclude that for assessment of nutritional status body composition should be investigated taking into account body build in addition to age and sex.     

Bias and limits of agreement between hydrodensitometry, bioelectrical impedance and skinfold calipers measures of percentage body fat

Previous research has often used correlations as a statistical method to show agreement; however, this is not a valid use of the statistic. The purpose of this study was to investigate the bias and limits of agreement for three methods of estimating percentage body fat for 117 male and 114 female university athletes: hydrodensitometry (HYD), bioelectrical impedance (BIA) and skinfold calipers (SKF). The mean (SD) percentage body fat for males as assessed by HYD, BIA and SKF methods, respectively, were 13.2 (3.3)%, 14.1 (3.3)% and 13.0 (3.2)%. Female body fat measurements were 22.5 (3.9)%, 23.7 (4.3)% and 23.8 (4.2)%, respectively. Pearson product moment correlations for male and female body fat percentages between the three methods were high, ranging from 0.81 to 0.86 (P < 0.05). However, compared to the criterion measure of body fat percentage (HYD), the magnitude of agreement BIA and SKF revealed a different pattern. The mean absolute difference between HYD and BIA measurements of body fat for males was −0.8 (2.0)% fat, and between HYD and SKF was it was 0.2 (1.7)% fat. The mean absolute difference for females between HYD and BIA was −1.2 (2.5)%; for HYD and SKF it was −1.4 (2.2)%. Compared to the HYD measures for males and females, the BIA and SKF measures were as much as a 3.8% underestimation and a 6.2% overestimation of body fat. This study provides evidence that the strength of a correlation does not indicate agreement between two methods. In future, reliability and validity studies should examine the absolute differences between two variables and calculate limits of agreement around which a practitioner can appreciate the precision of the methodologies. Accepted: 26 August 1997     

Equation for estimating total body water by bioelectrical impedance measurements in Japanese subjects]

This article reports a study in which the equation for total body water (TBW) estimated from deuterium (2H2O)-dilution method and bioelectrical impedance measurement (BIM) is described. Subjects were 60 healthy males aged 30 +/- 18.3 yr (18-74) and 31 healthy females aged 37 +/- 17.5 yr (19-70). Total body water determined by the analysis of the dilution of orally ingested deuterium oxide (1g2H2O, 99.75 atom % excess/kg body weight) in urine. Bioelectrical impedance was measured for each subjects in a supine position using an electrical impedance analyzer (500 microA, 50kHz, T-1988K, Toyo Physical Inc.) with a four electrodes (Y-250, Nihon Kohden). The mean values of total body water and the impedance in males and females subjects were 34.1 +/- 4.27 l and 25.7 +/- 2.42 l, 567 +/- 28.5 omega and 562 +/- 32.5 omega, respectively. Height squared divided by resistance (Ht2/R) correlated well with TBW as measured by 2H2 O, r = 0.530 (p less than 0.001) in males and r = 0.782 (p less than 0.001) in females. The best-fitting regression equation to predict TBW comprised Ht2/R(X1) and body weight (X2) (R = 0.915, SEE = 1.70 l in males and R = 0.834, SEE = 1.28 l in females). Equations were provided with BIM instrument for the prediction of TBW: for males TBW, l = 0.1983X1 + 0.4004X2 - 0.7938 and for females TBW, l = 0.3536X1 + 0.1269X2 + 3.3417. These results suggest that bioelectrical impedance measurement is a useful measure of total body water in Japanese subjects.     

Effects of orthostatic fluid shifts on bioelectrical impedance measurements

This study analyzes the effect of orthostatic fluid shift caused by body postural changes on the reliability and stability of bioelectrical impedance. It has been found that following a fluid distribution perturbation caused by postural changes, impedance values change for a period of time that can be longer than the measurement time. Based on these preliminary measurements, it is recommended that new measurement protocols for bioelectrical impedance be developed in order to minimize perturbations on existing fluid distribution, thus increasing the reliability of bioelectrical impedance data.     

Body composition assessment of young tennis players by multi-frequency impedance measurements

Body composition was estimated in 169 young tennis players using the multi-frequency impedance method to predict their fatfree-mass, fat, extra-cellular water, and total body water. Bioelectrical impedances at 1, 5, 10, 50 and 100 kHz were determined. Ratios of impedance at low to high frequencies (Z1/Z100; Z5/Z100) were also used as indicators of body water distribution. This sample is characterized by a greater body mass — fat mass, above all-than other Italian sport participants. Sexual dimorphism in body composition is also evident in this sample. The parameters of body composition, predicted by impedance measurements were compared with parameters obtained through other methods (skinfolds and BMI) on the same subjects. Results varied considerably, in relation to the various equations or different techniques employed. Besides demonstrating the value of multifrequency impedance measurements in the assessment of body composition, our findings indicate the necessity of further methodological research to validate the method under controlled conditions.     

Ethnic differences in the relationship between bioelectrical impedance and body size

The present study compared the regression equations of bioelectrical impedance on body size among various groups to investigate potential differences due to ethnicity. Data consisted of 30 Japanese and 28 Caucasoid subjects, and other groups of Aborigines, Danes, Melanesians and Polynesians from literature. The relationship between impedance and body weight fot the groups showed the ethnic difference. In the regression equations for Japanese and Caucasoid, a statistically significant difference was observed between both groups. The regression equation for Japanese was lower in the elevation. This seemed to be attributable to differences in the volume of fat-free mass for the same body build, configuration of the body, and fat-free mass density.     

Body composition of young laborers: the results of a bioelectrical impedance analysis

The aim of this study was to determine the changes caused by physical stress on the body composition of young males. In order to show these changes, the study was performed with 104 young male laborers who worked through their adolescence and who were currently working in workshops in the industrial sector (Group 1, mean age 18.48 +/- 0.61 years). For the control group, two groups of the same age but having a difference in terms of socioeconomic status were chosen. The first one of these was comprised of individuals who had the same socioeconomic status as the laborers (Group 2, n = 102, mean age 18.39 +/- 0.58 years) but were not laborers. The second control group was composed of individuals from the higher socioeconomic levels of society (Group 3, n = 103, mean age 18.43 +/- 0.67). Measurements of the height of the individuals were taken with a standard portable anthropometer, and their body weight and BIA measurements were taken with Tanita TBF-305 leg-to-leg body composition analysis equipment. The results of the analysis show that the weight, height, BMI and fat mass values of the laborers were significantly lower (P < 0.05-0.001) than those of Group 3, but were not statistically different from those of Group 2. These findings reveal that the effects of socioeconomic conditions on body composition outweigh those of working conditions.     

Comparison of proximal and distal placements of electrodes to assess body composition by bioelectrical impedance in obese adults

The purpose of this study was to compare the variability and accuracy of proximal and traditional distal electrode placement to estimate body composition in obese adults. Fifty-two obese men and women had a mean age of 37 years and an average body mass index (BMI) of 30.6 kg.m(-2). Body composition was measured using DEXA and an RJL bioelectric impedance analysis 101A bioelectric impedance analyzer. Impedance was measured using the traditional distal electrode placement (hand and foot) and a proximal electrode placement where the current detecting electrodes were placed in the antecubital and popliteal fossae. The distal resistance was 482.4 +/- 79 Omega, which was more than double the mean proximal values of 193.2 +/- 27 Omega. Multiple regression analysis derived the best-fitting equation to predict DEXA-derived fat-free mass. The combination of Ht(2)/R (height(2)/resistance) and mass were the only significant predictors for both the proximal and distal electrode placements. The resulting R(2) values were 0.86 and 0.88, whereas standard errors of the estimate (SEEs) were 4.0 and 3.6 kg for the distal and proximal placements, respectively. An independent sample of 40 obese women was used to cross-validate this new equation. Mean impedance predictions using the distal and proximal electrode placements (45.78 +/- 1.07 and 45.29 +/- 0.97 Omega, respectively) were similar to the reference values (45.29 +/- 0.64 Omega) determined by DEXA. Fat-free mass predicted with the distal and proximal electrode placements correlated significantly (p < 0.001) with the reference fat-free mass value (r = 0.72 and 0.75, respectively). These data suggest that using a proximal electrode placement and a fatness-specific equation helps to reduce the variability of the bioelectric impedance analysis technique in obese adults.