Estimation of human body composition by electrical impedance methods: a comparative study

This study 1) further validated the relationship between total body electrical conductivity (TOBEC) and densitometrically determined lean body mass (LBMd) and 2) compared with existing body composition techniques (densitometry, total body water, total body potassium, and anthropometry) two new electrical methods for the estimation of LBM: TOBEC, a uniform current induction method, and bioelectrical impedance analysis (BIA), a localized current injection method. In a sample of 75 male and female subjects ranging from 4.9 to 54.9% body fat the correlation between LBMd and LBM predicted from TOBEC by use of a previously developed regression equation was extremely strong (r = 0.962), thus confirming the validity of the TOBEC method. LBM predicted from BIA by use of prediction equations provided with the instrument also correlated with LBMd (r = 0.912) but overestimated LBM compared with LBMd in obese subjects. However, no such systematic error was apparent when new prediction equations derived from this heterogeneous sample of subjects were applied. Thus the TOBEC and BIA methods, which are based on the differing electrical properties of lean tissue and fat and which are convenient, rapid, and safe, correlate well with more cumbersome human body composition techniques.     

Cross-Validation of Fat-Free Mass Estimated From Body Density Against Bioelectrical Resistance: Effects of Obesity and Gender

GORAN, MICHAEL I AND M ABU KHALED. Cross-validation of fat-free mass estimated from body density against bioelectrical resistance: effects of obesity and gender. Obes Res. The major purpose of this study was to examine whether estimates of body composition from bioelectrical resistance were systematically biased by obesity and/or gender (using hydrodensitometry as a comparison method). We compared fat-free mass (FFM) by bioelectrical resistance (BR) using 5 equations (Lukaski, Kushner, Rising, Khaled, and Segal) to FFM by hydrodensitometry (HD) in 20 lean men, 30 lean women, 33 obese men and 22 obese women. None of the BR equations was successfully cross-validated against FFM by HD in all 4 sub-groups. The Lukaski equation significantly underestimated FFM in all 4 groups by 2.7 to 4.7 kg; the Kushner equation significantly underestimated FFM by 2.0 to 2.9 kg except in obese women; the Rising equation significantly overestimated FFM in obese women (5.3 kg) and men (2.9 kg); the Khaled equation successfully predicted FFM in all groups except obese men; and the Segal equation successfully predicted FFM in all groups except lean men. In some groups, a portion of the discrepancy could be explained by bias originating from body fat. Analysis of our data by forward regression analysis demonstrated that height²/resistance, body weight, gender and suprailiac skinfold thickness provide the most accurate estimates of FFM (R²=0.92; SEE = 3.58kg) that are free of bias originating from gender and body fat. We conclude that the estimation of fat-free mass by BR is significantly influenced by gender and obesity. An alternative equation is proposed for estimating fat-free mass based on measurement of height²/resistance, body weight, gender and suprailiac skinfold thickness.     

Sex differences in the distribution of subcutaneous and internal fat

One-hundred twenty-one male and 93 female subjects, aged 18-23 years, were selected for an investigation of the proportion of subcutaneous to total fat in the whole body. Body fat mass was calculated from body density using the Siri equation. Subcutaneous fat mass was calculated by measuring skinfold thickness at 15 sites and using a modification of the equation derived by Skerjl, Brozek, and Hunt. The main modification to this equation was the introduction of a midlayer area of subcutaneous tissue that is multiplied by fat thickness to give fat volume. The outermost body surface area, which has been utilized in previous research, results in an overestimation of the true subcutaneous fat mass. The average percentages of fat situated subcutaneously (PFSSs) were calculated as 53.7% for males and 62.6% for females. This sex difference is also seen in correlation-regression analysis of PFSS and percentage of fat. In females PFSS decreases with increasing total percentage of fat, whereas in males there is no significant relationship between PFSS and total percentage of fat. This suggests that the proportion of subcutaneous to total fat distribution is negatively related to fatness in females.     

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.     

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.     

人工饲养条件下根田鼠肥满度的研究

实验室条件下,利用根田鼠1～70日龄体重和体长数据,计算其肥满度指数,目的在于分析其生长发育的基本规律。结果表明,根田鼠1～70日龄肥满度存在性别差异且随日龄增加而增大;雌雄个体的发育不同步;常见曲线回归模型对根田鼠1～70日龄的肥满度不能准确拟合,根据其生长发育状况,将其划分为3个阶段(其中幼体和成体阶段各含2个阶段)。     

Thyroid volume as measured by ultrasonography in patients With type 1 diabetes mellitus without thyroid dysfunction.

The aim of this cross-sectional study was to assess and compare thyroid volume and its derminants in a cohort of type 1 diabetes mellitus (DM1) and compare the results to a healthy control group. We studied 65 DM1 patients treated with an intensive insulin regimen and 65 matched controls. In all participants we evaluated weight, height, BMI, waist-hip ratio, body surface area and body composition variables determined by using a bioelectrical impedance analyser. Thyroid size was estimated by ultrasonography. We determined basal TSH, anti-thyroid antibodies and urinary iodine excretion. Body weight, height, BMI and body surface area were similar in DM1 patients and in controls. Fat-free mass was higher in both male and female DM1 patients than in controls (64.4 +/- 6.9 vs. 60.4 +/- 8.2 kg, p=0.03 and 48.3 +/- 5.7 vs. 45.4 +/- 6, p=0.04, respectively), and fat mass was lower in male DM1 patients than in controls (9.7 +/- 7 vs. 14.2 +/- 8.1 kg, p=0.01). Thyroid volume was greater in both male and female DM1 patients than in controls (11.12 +/- 2.87 vs. 9.63 +/- 2.27 ml, p=0.0001 and 9.5 +/- 2.3 vs. 7.7 +/- 2 ml, p=0.002, respectively). Urinary iodine excretion was similar in the two groups. In both DM1 patients and controls, thyroid volume correlated with weight, height, BMI, waist-hip ratio, body surface area, fat-free mass and the multivariate linear regression analysis with thyroid volume as the dependent variable showed that fat-free mass in either group was the only significant determinant of thyroid volume. We conclude that DM1 patients had larger thyroid volume compared with healthy controls with similar anthropometry; body composition is different in DM1 patients and that the anthropometric and body composition variables, especially fat-free mass and body surface area, predict thyroid volume either in DM1 patients or in healthy controls.     

Fat, muscles, and wages

Recent studies in health economics have generated two important findings: that as a measure of fatness the body mass index (BMI) is biased; and that, when it comes to analyzing wage correlates, both fat-free mass (FFM) and body fat (BF) are better suited to the task. We validate these findings for Germany using the BIAdata Base Project and the German Socio-Economic Panel. While we find no significant correlation between BMI and wages in any of our models, simple linear regression models featuring both contemporary and time-lagged fatness measures indicate that FFM and, to a lesser extent, BF are associated with hourly wages: more specifically, the relationship between FFM/BF and hourly wages is about two to three times higher for females than for males. In contrast, fixed-effects models indicate that there is no correlation between hourly wages and both FFM and BF with one exception: a significant correlation (and one in line with expectations) is found to be the rule among job changers.     

Body composition in adolescents: estimation by total body electrical conductivity

This comparative study, conducted on 28 boys and girls of widely varying fatness, was designed to validate a new whole-body composition method [total body electrical conductivity (TOBEC)], based on bioelectrical properties of the human body. A significant correlation [r = 0.911; standard error of the estimate (SEE) = 5.3 kg] was demonstrated between the transformed TOBEC scores (TOBEC0.5 X Ht) and lean body mass (LBM) determined by hydrodensitometry and corrected for individual variations in hydration (LBMd + W). TOBEC determinations also correlated well with 1) total body water determined by deuterium oxide dilution (r = 0.877; SEE = 4.5 liters), 2) total body potassium determined by means of a 4 pi whole-body counter (r = 0.860; SEE = 430.7 meq), 3) LBM derived from skinfold thicknesses (r = 0.850; SEE = 5.8 kg). The residuals of the regression between LBMd + W and TOBEC scores did not show any significant correlation with either the potassium or the water content of the LBM. The results indicate that TOBEC is a simple, rapid, reliable, and noninvasive technique for delineating changes in body composition that occur in children during growth.     

Bioelectrical impedance estimation of fat-free body mass in children and youth: a cross-validation study.

The purposes of this study were to develop and cross-validate the "best" prediction equations for estimating fat-free body mass (FFB) from bioelectrical impedance in children and youth. Predictor variables included height2/resistance (RI) and RI with anthropometric data. FFB was determined from body density (underwater weighing) and body water (deuterium dilution) (FFB-DW) and from age-corrected density equations, which account for variations in FFB water and bone content. Prediction equations were developed using multiple regression analyses in the validation sample (n = 94) and cross-validated in three other samples (n = 131). R2 and standard error of the estimate (SEE) values ranged from 0.80 to 0.95 and 1.3 to 3.7 kg, respectively. The four samples were then combined to develop a recommended equation for estimating FFB from three regression models. R2 and SEE values and coefficients of variation from these regression equations ranged from 0.91 to 0.95, 2.1 to 2.9 kg, and 5.1 to 7.0%, respectively. As a result of all cross-validation analyses, we recommend the equation FFB-DW = 0.61 RI + 0.25 body weight + 1.31, with a SEE of 2.1 kg and adjusted R2 of 0.95. This study demonstrated that RI with body weight can predict FFB with good accuracy in Whites 10-19 yr old.     

Reliability and validity of body composition measures in female athletes.

The purpose of this investigation was to determine the reliability and validity of bioelectrical impedance (BIA) and near-infrared interactance (NIR) for estimating body composition in female athletes. Dual-energy X-ray absorptiometry was used as the criterion measure for fat-free mass (FFM). Studies were performed in 132 athletes [age = 20.4 +/- 1.5 (SD) yr]. Intraclass reliabilities (repeat and single trial) were 0.987-0.997 for BIA (resistance and reactance) and 0.957-0.980 for NIR (optical densities). Validity of BIA and NIR was assessed by double cross-validation. Because correlations were high (r = 0.969-0.983) and prediction errors low, a single equation was developed by using all 132 subjects for both BIA and NIR. Also, an equation was developed for all subjects by using height and weight only. Results from dual-energy X-ray absorptiometry analysis showed FFM = 49.5 +/- 6.0 kg, which corresponded to %body fat (%BF) of 20.4 +/- 3.1%. BIA predicted FFM at 49.4 +/- 5.9 kg (r = 0.981, SEE = 1.1), and NIR prediction was 49. 5 +/- 5.8 kg (r = 0.975, SEE = 1.2). Height and weight alone predicted FFM at 49.4 +/- 5.7 kg (r = 0.961, SEE = 1.6). When converted to %BF, prediction errors were approximately 1.8% for BIA and NIR and 2.9% for height and weight. Results showed BIA and NIR to be extremely reliable and valid techniques for estimating body composition in college-age female athletes.     

Ethnic Variability in Body Size,Proportions and Composition in Children Aged 5 to 11 Years: Is Ethnic-Specific Calibration of Bioelectrical Impedance Required?

Background

Bioelectrical Impedance Analysis (BIA) has the potential to be used widely as a method of assessing body fatness and composition, both in clinical and community settings. BIA provides bioelectrical properties, such as whole-body impedance which ideally needs to be calibrated against a gold-standard method in order to provide accurate estimates of fat-free mass. UK studies in older children and adolescents have shown that, when used in multi-ethnic populations, calibration equations need to include ethnic-specific terms, but whether this holds true for younger children remains to be elucidated. The aims of this study were to examine ethnic differences in body size, proportions and composition in children aged 5 to 11 years, and to establish the extent to which such differences could influence BIA calibration.

Methods

In a multi-ethnic population of 2171 London primary school-children (47% boys; 34% White, 29% Black African/Caribbean, 25% South Asian, 12% Other) detailed anthropometric measurements were performed and ethnic differences in body size and proportion were assessed. Ethnic differences in fat-free mass, derived by deuterium dilution, were further evaluated in a subsample of the population (n = 698). Multiple linear regression models were used to calibrate BIA against deuterium dilution.

Results

In children <11 years of age, Black African/Caribbean children were significantly taller, heavier and had larger body size than children of other ethnicities. They also had larger waist and limb girths and relatively longer legs. Despite these differences, ethnic-specific terms did not contribute significantly to the BIA calibration equation (Fat-free mass = 1.12+0.71*(height²/impedance)+0.18*weight).

Conclusion

Although clear ethnic differences in body size, proportions and composition were evident in this population of young children aged 5 to 11 years, an ethnic-specific BIA calibration equation was not required.     

Fat mass deposition during pregnancy using a four-component model.

Estimates of body fat mass gained during human pregnancy are necessary to assess the composition of gestational weight gained and in studying energy requirements of reproduction. However, commonly used methods of measuring body composition are not valid during pregnancy. We used measurements of total body water (TBW), body density, and bone mineral content (BMC) to apply a four-component model to measure body fat gained in nine pregnant women. Measurements were made longitudinally from before conception; at 8-10, 24-26, and 34-36 wk gestation; and at 4-6 wk postpartum. TBW was measured by deuterium dilution, body density by hydrodensitometry, and BMC by dual-energy X-ray absorptiometry. Body protein was estimated by subtracting TBW and BMC from fat-free mass. By 36 wk of gestation, body weight increased 11.2 +/- 4.4 kg, TBW increased 5.6 +/- 3.3 kg, fat-free mass increased 6.5 +/- 3.4 kg, and fat mass increased 4.1 +/- 3.5 kg. The estimated energy cost of fat mass gained averaged 44,608 kcal (95% confidence interval, -31, 552-120,768 kcal). The large variability in the composition of gestational weight gained among the women was not explained by prepregnancy body composition or by energy intake. This variability makes it impossible to derive a single value for the energy cost of fat deposition to use in estimating the energy requirement of pregnancy.     

Relationship of upper body fat distribution to serum glucose and lipids in a Costa Rican population

Present models of the relation between subcutaneous fat distribution and serum biochemistries have been based largely on U.S. White populations. To determine interpopulational differences in that relation, we measured 68 clinically normal adult Costa Ricans aged 17-32. Data collected included six skinfolds: triceps, subscapular, suprailiac, umbilical, anterior mid-thigh, and medial calf; height, weight, and four fasting serum parameters: glucose, triglyceride, cholesterol, and high-density lipoprotein (HDL). Correlations between standardized skinfold ratios and biochemistries were highest--on the order of 0.40-0.50--for upper-lower body contrasts to triglyceride and cholesterol in males and to glucose and HDL in females. Canonical correlation analysis, with body mass index partialed out, found significant correlations for the first male variate and the first two female variates. The first male variate was positively weighted on subscapular fatness and on triglyceride and cholesterol, respectively. The two female skinfold variates were positively weighted on subscapular and on outer limbs, respectively, while their corresponding biochemical variates were weighted on glucose and triglyceride and on cholesterol and HDL, respectively. These findings are generally consistent with those based on U.S. populations but suggest that in non-Anglo populations, upper trunk fatness may be more relevant than anterior waist fatness to biochemical dysfunction.     

Effect of race and resistance training status on the density of fat-free mass and percent fat estimates.

The impact of race and resistance training status on the assumed density of the fat-free mass (D(FFM)) and estimates of body fatness via hydrodensitometry (%Fat(D)) vs. a four-component model (density, water, mineral; %Fat(D,W,M)) were determined in 45 men: white controls (W; n = 15), black controls (B; n = 15), and resistance-trained blacks (B-RT; n = 15). Body density by hydrostatic weighing, body water by deuterium dilution, and bone mineral by dual-energy X-ray absorptiometry were used to estimate %Fat(D,W,M). D(FFM) was not different between B and W (or 1.1 g/ml); however, D(FFM) in B-RT was significantly lower (1.091 +/- 0.012 g/ml; P < 0.05). Therefore, %Fat(D) using the Siri equation was not different from %Fat(D,W,M) in W (17.5 +/- 5.0 vs. 18.3 +/- 5.4%) or B (14.9 +/- 5.6 vs. 15.7 +/- 5.7%) but significantly overestimated %Fat(D,W,M) in B-RT (14.0 +/- 5.9 vs. 10.4 +/- 6.0%; P < 0.05). The use of a race-specific equation (assuming D(FFM) = 1.113 g/ml) did not improve the agreement between %Fat(D) and %Fat(D,W,M), resulting in a significantly greater mean (+/-SD) discrepancy for B (1.7 +/- 1.8% fat) and B-RT (6.2 +/- 4.3% fat). Thus race per se does not affect D(FFM) or estimates of %Fat(D); however, B-RT have a D(FFM) lower than 1.1 g/ml, leading to an overestimation of %Fat(D).     

Relations among measures of body composition, age, and sex in the common marmoset monkey (Callithrix jacchus)

Few studies of body composition have been done in New World primates. In the study reported here, four methods of assessing body composition (body weight, anthropometry, labeled-water dilution, and total body electroconductivity) were compared in 20 marmosets, aged 0.96 to 7.97 years. Males and females did not differ in any measure (P > 0.05). Body weight ranged from 272 to 466 g, and body fat estimates varied from 1.6 to 19.5%. Strong positive correlations were observed between total body water and total body electroconductivity (R2 = 0.77), body weight and fat-free mass (males R2 = 0.95; females R2 = 0.91), and body weight and fat mass (males R2 = 0.86; females R2 = 0.85; P < 0.01). Male and female slopes were equivalent (P > 0.05) for the regressions of fat and fat-free mass against body weight. Positive correlations also were observed between girth measures and fat-free mass (R2 = 0.48 to 0.78) and fat mass (R2 = 0.60 to 0.74; P < 0.01). A good second- order polynomial relationship was observed between age and fat-free mass for the combined sample (R2 = 0.64). Results indicated that: subjects were lean; there was no sexual dimorphism relative to measures; body weight provided a reliable estimate of fat and fat-free mass; and within-subject body weight changes reflected a similar relationship between body weight and fat-free mass as did that across subjects.     

Basal and insulin-regulated free fatty acid and glucose metabolism in humans

These studies were done to examine the effects of body composition, resting energy expenditure (REE), sex, and fitness on basal and insulin-regulated FFA and glucose metabolism. We performed 137 experiments in 101 nondiabetic, premenopausal women and men, ranging from low normal weight to class III obese (BMI 18.0-40.5 kg/m2). Glucose flux was measured using [6-(2)H2]glucose and FFA kinetics with [9,10-(3)H]oleate under either basal (74 experiments) or euglycemic hyperinsulinemic (1.0 mU.kg FFM(-1).min(-1)) clamp conditions (63 experiments). Consistent with our previous findings, REE and sex independently predicted basal FFA flux, whereas fat-free mass was the best predictor of basal glucose flux; in addition, percent body fat was independently and positively associated with basal glucose flux (total r2 = 0.52, P < 0.0001). Insulin-suppressed lipolysis remained significantly associated with REE (r = 0.25, P < 0.05), but percent body fat also contributed (total adjusted r2 = 0.36, P < 0.0001), whereas sex was not significantly related to insulin-suppressed FFA flux. Glucose disposal during hyperinsulinemia was independently associated with peak VO2, percent body fat, and FFA concentrations (total r2 = 0.63, P < 0.0001) but not with sex. We conclude that basal glucose production is independently related to both FFM and body fatness. In addition, hyperinsulinemia obscures the sex differences in FFA release relative to REE, but brings out the effects of fatness on lipolysis.     

Vital capacity in trained and untrained healthy young adults in the Netherlands

Slow inspiratory vital capacity was measured in 226 healthy young adults, aged from 17 to 35 years. The group included 119 men and 107 women, 87 trained subjects, 71 untrained subjects who intended to take part in a training program for competitive rowing, and 68 untrained subjects who never took part in any competitive sport. The vital capacity increased with height, weight, fat-free mass, height X fat-free mass, and height-independent fat-free mass, with men having significantly higher vital capacities than women of the same height or weight. In both males and females vital capacity showed the best relation with height X fat-free mass (correlation coefficients are 0.78 and 0.57 respectively). Multiple regression on vital capacity with height, weight, fat-free mass, height X fat-free mass, height-independent fat-free mass, percentage body fat, and age increased the correlation coefficient only slightly (0.80 and 0.59 respectively). The subjects had vital capacities that were much higher than those predicted for them by equations originating from the USA. There was no difference between the observed vital capacities and those predicted by equations originating from Europe. There is a difference in vital capacity between the European subjects studied and subjects of similar height studied in the USA. This implies that equations derived from subjects in the USA cannot be applied to European subjects. From our results we conclude that vital capacity is not increased by physical activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors influencing male mating behaviour in Gambusia affinis (Baird & Girard) with a coercive mating system

The effects of male and female body size, and correlated characteristics, on male mating behaviour were investigated in the western mosquitofish Gambusia affinis . Because larger females typically have larger broods in Gambusia sp., it was predicted that males would attempt more copulations with larger females. Two-way ANOVA showed that female body size was a significant predictor of male mating behaviour but male size was not. The effects of a suite of additional traits (both male and female) on male mating attempts were also tested. In a stepwise multiple regression, female standard length ( L _S), size of the female gravid spot and male testes mass were significant predictors of male mating attempts, accounting for c. 27% of variation in male mating. Path analysis showed that differences between male and female L _S, male body condition and male testes mass were significant predictors of male mating attempts, and also accounted for 27% of the variation in male mating attempts. The two statistical models were very similar in their predictive power, but differed slightly in significant predictor variables. Results confirm that factors other than female size are important predictors of male mating behaviour in the western mosquitofish.     

中西太平洋鲣鱼的年龄鉴定和生长特性

鱼类的年龄和生长等生物学参数对于准确评估渔业资源非常重要.本文于2007年10月至2008年1月,利用围网渔船在中西太平洋海域采集了262尾鲣鱼样本,现场测定其叉长（278～746 mm）和体质量（345～9905 g）,并搜集第一背鳍鳍棘用于鉴定其年龄和生长状况.结果表明：鲣鱼叉长（L, mm）与体质量(M,g)的关系式为M=3.612×10^-6L^{3. 278} （R²=0.9782）,性别对其影响不显著（F=2.002,P>0.05）;经赤池信息量标准（AIC）评估,在幂函数、线性及指数3种回归关系中,线性回归模型最好地拟合了鲣鱼叉长与鳍棘截面半径之间的关系(AIC=2257.4);采用Fraser-Lee法求得的鲣鱼1～5龄平均逆算叉长分别为398.4、494.2、555.4、636.8和728.8 mm;经残差平方和分析,雌雄鲣鱼的生长状况间不存在显著性差异(F=0.670;df=182;P>0.05),推得鲣鱼von Bertalanffy生长方程为L_t=706.51(1-e^{-0.64(t+0.037)}).