Skeletal differences between black and white men and their relevance to body composition estimates

Skeletal differences exist between closely matched Black and White women, although it is unknown if similar differences also exist between Black and White men after controlling for age, body weight, and stature. The aim of this study was twofold: to test the hypothesis that Black men have greater bone mass, higher bone mineral density, and longer limbs compared to White men of similar age, weight, and height; and second, to establish if ethnic variation in skeletal characteristics has an impact on the models upon which three widely used methods for estimating total body fat are based. Twenty-four healthy Black men were matched by age (±5 years), height (±3 cm), and weight (±2 kg) to 24 healthy White men. Skeletal characteristics and body composition were studied using anatomical and compartment estimates derived by anthropometry, ³H₂O dilution, hydrodensitometry, whole-body ⁴⁰K counting, and dual photon systems. Black men had greater bone mineral mass (P = 0.007), higher bone density (P = 0.054), longer femurs (P = 0.002), longer anthropometric arm and thigh lengths (P = 0.001 and P = 0.002, respectively), lower spine to femur ratio (P = 0.004), and similar spine length (P = 0.271) compared to White men. Total body fat and fat-free body mass (FFM) were estimated in the men using a four-compartment model. Black and White men had similar total body fat, K (TBK), water (TBW), and FFM. Density of FFM and TBK/FFM were also similar between Black and White men, suggesting that current two-compartment hydrodensitometry and TBK models for estimating fat may not require adjustments for ethnicity. The TBW/FFM ratio, which is the main assumed steady-state relation for the two-compartment TBW method of estimating fat, was modestly increased (P = 0.05) in Black men (x? ± SD, 0.744 ± 0.018) compared to White men (0.732 ± 0.021). These results confirm that Black and White men differ significantly in some skeletal characteristics and these differences have implications in the study of both osteoporosis and human body composition. © 1994 Wiley-Liss, Inc.     

Relative and interacting effects of sex,race, and environment upon body cell mass in healthy adults

Most epidemiologic studies in nutrition have concentrated on body fat and obesity because of associated health risks, while few studies have examined factors that influence body cell mass (BCM). The relative influences of sex, race, environment, and age upon BCM were compared by analyzing the results of bioimpedance analyses in two cohorts of 1094 healthy adults, including Africans in Zaire, plus African Americans and Caucasians in New York City. Men were taller, heavier, and had a larger BCM and fat-free mass (FFM) than women, while women had more fat than men. African American men and women had more BCM, FFM, and fat than Africans. In contrast, BCM and FFM were not different in African Americans and Caucasians, and body fat was higher only in African American than in Caucasian women. Sex influenced the effects of environment and race, since the majority of the weight differences in men were in FFM, while the majority of the weight differences in women were in fat. The effect of sex upon BCM was stronger than the effects of environment (p < 0.001) or race (p < 0.001), and the effect of environment was stronger than the effect of race (p = 0.012), so that the relative strengths were sex > environment > race. Race had a stronger effect upon FFM than upon BCM. Since race did not affect BCM significantly, it may affect other components of FFM, e.g., extracellular water or solids, such as skeletal mass. The results demonstrate that sex affects normal body composition to a greater degree than race or environment. Am. J. Hum. Biol. 10:259–268, 1998. © 1998 Wiley-Liss, Inc.     

Body fat by dual photon absorptiometry: Comparisons with traditional methods in Asians,blacks, and whites

Measurement of body fat by dual photon absorptiometry (Fat_DPA) is based on the physical principles of differential attenuation of discrete photons by fat and other soft tissue components. The three traditional methods of measuring fat are indirect, in that they depend on measuring the fat free mass (FFM) based on the assumed constancy of water, potassium, and density in the FFM. Comparison of Fat_DPA with fat measured by each of the indirect methods discloses systematic differences which shed light on the nature of the constancy assumptions. The purpose of this report is to study the effects of sex, age, and fatness, as well as race, on the traditional methods for estimating body fat%. In Asians (99 m, 109 f), blacks (64 m, 48 f), and whites (166 m, 212 f), 18 to 94 years, with body mass indices of 16 to 36 kg/m², body fat measured by DPA was compared with fat by three traditional methods: total body potassium (TBK; ⁴⁰K counting), total body water (TBW; HTO dilution), and underwater weighing (UWW). DPA showed the highest overall correlation with TBW and the lowest with UWW, among the three traditional methods. Asians showed the lowest correlations between Fat_DPA and Fat_UWW. On average, Fat_TBK was higher, while Fat_UWW was lower than Fat_DPA. The differences between Fat_DPA and Fat_OTHER by the three traditional methods were correlated with age with a negative slope in all groups, the steepest slope being for Fat_DPA – Fat_TBK in blacks. Correlations with fatness showed positive slopes for Fat_DPA – Fat_TBW and – Fat_UWW but not for – Fat_TBK. Fat_DPA could become a criterion method for body fat, particularly in the young, old or ill, where traditional “constants” become unreliable, if calibration can be accomplished throughout the range of subject size. Ethnicity, age, sex, and fatness as well as illness are potent variables affecting the composition of the FFM; direct measurements of fat are preferable, to avoid artifacts resulting from using indirect methods. © 1992 Wiley-Liss, Inc.     

Estimation of total body water by bioelectrical impedance analysis in blacks

Several differences exist between the body composition of blacks and whites. This study was designed to investigate the applicability of bioelectrical impedance analysis (BIA) in blacks, using prediction equations developed in whites. A multiple regression equation developed on 79 white adults, using deuterium oxide dilution space total body water (D₂O-TBW) as the reference method, was prospectively applied to 88 blacks aged 19–50 years. Although the regression line of D₂O-TBW on BIA-TBW was not significantly different from the line of identity (r = 0.98, SEE = 1.71 liters), mean TBW was significantly underestimated by 0.84 liter. Other BIA equations from the literature also underestimated D₂O-TBW in blacks, except for an equation developed on a mixed black and white population. Multiple regression analysis on the data of the black and white subjects combined showed that race, offered as a separate independent variable, improved the correlation with D₂O-TBW slightly but significantly (P < 0.01). It was concluded that BIA may be valuable in the assessment of body composition in blacks as well as in whites. In this study a small underestimation of TBW occurred in blacks, using (BIA) equations from whites. This may be due to racial differences in body composition or to factors unrelated to ethnicity.     

Body composition and body hydration in old age estimated by means of skinfold thickness and deuterium dilution.

In this study a group of 30 women and 30 men aged 60-90 years was examined. Body density was predicted from the sum of four skinfold thickness (SFT) as described by Durnin and Womersley (1974). Body composition, expressed as a percentage of total body weight as fat mass (FM) and fat free mass (FFM) was calculated by means of Siri's formula (Siri 1961). Total body water (TBW) was measured from the dilution of an oral deuterium dose and FFM calculated assuming a hydration of 73.2%. The FM% predicted from SFT showed a slight but not significant decreasing age trend from 28.3% to 25.4% in men, and from 40.3% to 37.8% in women. Body hydration (about 50% of body weight in men and 44% in women) remained constant throughout the age range. FFM obtained from TBW assuming a constant hydration of FFM, was found to be unchanged with age. FM% predicted from SFT was correlated with values obtained from TBW on an individual basis (R2 = 0.38; p less than 0.0001 in men and R2 = 0.31; p less than 0.002 in women), but the scatter was large. The Bland and Altman statistical analysis (Bland and Altman 1986) suggests that the discrepancy between the two estimates tends to be significantly more positive with increasing fatness of the subject. The assumption of a constant hydration of FFM between individuals and with advancing age was tested. The hydration of FFM was calculated as the ratio between TBW (from deuterium dilution) and FFM (estimated from SFT). The wide range of values (50% to 90%) suggests large inter-individual differences. The mean values were lower than commonly reported, and differed with age and sex. In men, FFM hydration steadily decreases with age from the 7th decade (70.2 +/- 7.7%) to the 10th decade (65.9 +/- 8.2%). Women showed higher average figures than those of men and a lower age-associated decline (72.5% and 68.5% respectively). Our results suggest that FFM hydration decreases with age, and this indicates the need to develop age-related correction factors in order to derive FFM from TBW in an elderly population.     

Assessment of body composition in adolescent subjects with anorexia nervosa by bioimpedance

Our main goal was to test various impedance methods for measuring body composition in adolescents with anorexia nervosa (AN) during refeeding therapy. A specific objective was to compare the information provided by a foot-to-foot impedancemeter (FFI) with that supplied by a medical multifrequency impedancemeter and by dual X-ray absorptiometry (DXA). We have monitored 13 young AN subjects and 17 healthy controls of a similar age group using a Xitron 4200 multifrequency impedancemeter measuring extracellular (ECW) and total body water (TBW) volumes and a Tefal Bodymaster FFI measuring weight (W), fat-free-mass (FFM) and body fat mass (FM). This Tefal device has been modified to measure in addition ECW and TBW resistances permitting to calculate ECW and TBW volumes using appropriate algorithms. In addition FFM and FM were measured by DXA on AN subjects. FFM measured by the FFI and the Xitron in AN subjects were found to be respectively 7.8% and 4.5% lower than FFM measured by DXA. TBW measured by FFI was not significantly different from that measured by Xitron in AN subjects and in controls. ECW measured by the FFI was not significantly different from that measured by Xitron in controls, but was in AN subjects. The body cell mass to (height)2 ratio was found to be significantly different between AN subjects and controls. The modified FFI was found to be simpler and quicker to use than the Xitron, while giving similar information.     

Cross-calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry for the assessment of total and appendicular body composition in healthy subjects aged 21-82 years

Aim: To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults. Research design: A cross-sectional study was carried out. Subjects: Sixty-eight females and 42 males aged 21-82 years participated in the study. Methods: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance ( R ) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs. Results: The resistance index (RI), i.e. the height 2 /resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM ( vs 0.57), 45% more variance of LTM arm ( vs 0.48) and 36% more variance of LTM leg ( vs 0.50) ( p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI &#50 sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM arm and LTM leg. Conclusion: Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.     

Cross-calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry for the assessment of total and appendicular body composition in healthy subjects aged 21-82 years

AIM: To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults. RESEARCH DESIGN: A cross-sectional study was carried out. SUBJECTS: Sixty-eight females and 42 males aged 21-82 years participated in the study. METHODS: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs. RESULTS: The resistance index (RI), i.e. the height(2)/resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM (vs 0.57), 45% more variance of LTM(arm) (vs 0.48) and 36% more variance of LTM(leg) (vs 0.50) (p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI x sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM(arm) and LTM(leg). CONCLUSION: Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.     

Prediction of total body water and fatness from anthropometry: Importance of skinfold measurements

Prediction equations for total body water (TBW) generally use weight and height as predictors, but their ability may be limited because they implicitly assume a constancy of TBW among individuals of similar body size. The objective of this study was to evaluate the relative importance of anthropometric dimensions in predicting TBW and body composition. TBW determined by doubly labeled water (DLW) dilution techniques was used as the frame of reference in 23 healthy Aymara subjects, 4–65 years, in a rural community of the Bolivian Andes. Predictive performances of anthropometric variables for TBW were examined with multiple regression analyses. The generated equations were tested for cross-validity, using published data for U.S. adults. The resulting errors were compared with those of the published prediction equations of Mellits and Cheek (M&C) and Durnin and Womersley (D&W). The simplified prediction equation using weight and the triceps skinfold (Eq-A1:R² = 0.989, SEE = 1.041 L) and that using weight and the triceps and subscapular skinfolds (Eq-A2: R² = 0.990, SEE = 1.020 L) had better R² and smaller SEE than those using any combination of variables, weight, height, age, and sex. In the cross-validation sample, Eq-A1 and Eq-A2 demonstrated higher precision than the D&W and M&C equations. Evaluated by the method of Bland and Altman (mean difference ± 2SD), prediction errors for fat mass and fat percent were 0.2 ± 2.8 kg and 0.4 ± 5.2% in Eq-A2, 1.1 ± 3.5 kg, and 1.8 ± 6.1% in Eq-A1, −2.4 ± 3.6 kg and −3.4 ± 5.1% in D&W, and −2.3 ± 7.6 kg and −2.6 ± 10.3% in M&C. Significant underestimation of fat mass and sex differences in the biases were observed with D&W and M&C (P < 0.05), but not with Eq-A2. By including skinfold measurements, a single prediction equation for TBW was valid for males and females across different population samples. © 1996 Wiley-Liss, Inc.     

Development of anthropometry-based equations for the estimation of the total body water in Koreans

For developing race-specific anthropometry-based total body water (TBW) equations, we measured TBW using bioelectrical impedance analysis (TBW(BIA)) in 2,943 healthy Korean adults. Among them, 2,223 were used as a reference group. Two equations (TBW(K1) and TBW(K2)) were developed based on age, sex, height, and body weight. The adjusted R2 was 0.908 for TBW(K1) and 0.910 for TBW(K2). The remaining 720 subjects were used for the validation of our results. Watson (TBW(W)) and Hume-Weyers (TBW(H)) formulas were also used. In men, TBW(BIA) showed the highest correlation with TBW(H), followed by TBW(K1), TBW(K2) and TBW(W). TBW(K1) and TBW(K2) showed the lower root mean square errors (RMSE) and mean prediction errors (ME) than TBW(W) and TBW(H). On the Bland-Altman plot, the correlations between the differences and means were smaller for TBW(K2) than for TBW(K1). On the contrary, TBW(BIA) showed the highest correlation with TBW(W), followed by TBW(K2), TBW(K1), and TBW(H) in females. RMSE was smallest in TBW(W), followed by TBW(K2), TBW(K1) and TBW(H). ME was closest to zero for TBW(K2), followed by TBW(K1), TBW(W) and TBW(H). The correlation coefficients between the means and differences were highest in TBW(W), and lowest in TBW(K2). In conclusion, TBW(K2) provides better accuracy with a smaller bias than the TBW(W) or TBW(H) in males. TBW(K2) shows a similar accuracy, but with a smaller bias than TBW(W) in females.     

Body measurement variability,fatness, and fat‐free mass in children 8, 11, and 14 years of age: Project HeartBeat!

Project HeartBeat! is a four year mixed‐longitudinal study of the development of cardiovascular risk factors in White and African American children who at baseline comprised three age cohorts 8, 11, and 14 years. This paper focuses on the anthropometric variables which were chosen to reflect body fat and fat‐free mass. Selected anthropometric dimensions are compared with those of samples from the combined National Health and Nutrition Examination Surveys I and II to explore the similarities of the samples in terms of central tendencies and variances. The measurements were then explored in terms of their ability to estimate the two compartment model of body composition: fat‐free mass (FFM) and body fat (BF) from bioelectrical impedance (BIA). Project HeartBeat! children are slightly larger than NHANES children and have variances that are generally comparable to the national surveys. Over seven percent (7.7%) of children were overweight (BMI) and 25% had ‘mild obesity’ by %BF. Three different factor analytic methods (incomplete principal components, alpha and maximum likelihood) produced two latent variables from 17 anthropometric dimensions which together accounted for 76–83% of the variation: (1) A body mass factor (F1) which was weighted highly on six circumferences, weight and six skinfolds, and (2) a linear growth factor (F2) which was strongly associated with height, arm length, and sitting height. Triceps, subscapular and midaxillary skinfolds were consistently highly loaded on the body mass factor and their sum was highly correlated to %BF and fat mass (0.90–0.99). This suggests that this sum could be used to estimate fatness in children in studies where the BIA or other body composition techniques are unavailable. FFM and %BF were predicted from the anthropometric factors. Both factors contributed to the estimate of FFM (R² = 0.81–0.93), although F2 contributed proportionately more. The ‘body mass’ factor (F1) was the main predictor of %BF (R² = 0.86–0.93), though at some ages the linear factor (F2) was significantly and negatively related to %BF. This set of anthropometric dimensions, taken for the purpose of estimating body composition and summarized as two latent vectors by factor analysis, strongly reflects body fat and FFM in children and adolescents. Am. J. Hum. Biol. 11:69–78, 1999. © 1999 Wiley‐Liss, Inc.     

Determination of total body water by multifrequency bio-electric impedance: development of several models

Multifrequency bio-electronic impedance analysis (MF BIA) measurements are taken from a heterogeneous group of patients, varying in size between obese and slim. The measuring system uses four electrodes: two current and two potential electrodes. Three new models are developed to calculate total body water (TBW) from the BIA data, and the resulting TBW values are compared with TBW determined by D₂O dilution. The results demonstrate that the most simple model provides the best TBW values. For individual patients, TBW can be determined by means of bioimpedance measurement with an accuracy of 3 litres. In the most simple model (model 1), the body is electrically represented by a cylinder, and corrections are made for the amount of fat. This is an extension of the model used by Xitron. In the more advanced models (2 and 3), the body is represented by a cylinder for the trunk, and truncated cones represent the arms and legs. In model 2, ΔTBW amounts to 3 litres. It is shown that the resistance of the trunk is proportional to the square root of the length. In model 3, it is assumed that subcutaneous fat is a poor conductor if electric current. An equation is developed that describes the partition of subcutaneous fat, and the fat layer is then removed from the cones representing arms and legs and from the cylinder that models the trunk.     

Assessment of total body potassium in healthy Italian men

Background: Whole-body ⁴⁰K counting is a valuable tool for assessing cellular changes in body composition with ageing.

Aim: The objectives of this study were to assess total body potassium (TBK) and body cell mass (BCM) differences with age, and to compare TBK and BCM between individuals with a body mass index (BMI)?<25?kg?m^?2 versus?>25?kg?m^?2.

Subjects and methods: Body composition of 840 healthy Italian men, 18–70 years of age, was measured by whole-body counting of ⁴⁰K. BCM?(kg) was calculated as 0.00833?×?TBK?(mmol).

Results: Body weight did not differ among groups. TBK, TBK/height, TBK/body weight, and BCM were significantly lower for the 51–70-year-old group compared with all other groups. The 51–70-year-old group with a BMI?<?25?kg?m^?2 had significantly lower TBK, TBK/height, and BCM than all other decades with a BMI?<?25?kg?m^?2; whereas TBK/body weight was significantly lower than the 18–30 and 31–40-year-old groups. The 51–70-year-old group with a BMI?>?25?kg?m^?2 had significantly lower TBK, TBK/height, TBK/body weight, and BCM than all other decades with a BMI?>?25?kg?m^?2.

Conclusion: TBK and BCM decrease significantly with ageing, which could result in decreased functional capacity in older adults.     

Relationship between body composition and the components of somatotype

In a sample of 422 adults (200 females and 222 males) aged 18–73 years, the relationship was determined between somatotype estimated by the Health-Carter (Am. J. Phys. Anthropol. 27:57–74, 1967) method and body composition variables determined by using hydrodensitometry (HD) and Bioelectrical Impedance Analysis (BIA). The anthropometric (ANC) dimensions used to estimate somatotype were positively correlated with the endomorphic and mesmorphic components and negatively correlated with the ectomorphic component. For the BIA measurements, resistance (R) was negatively correlated with the mesomorphic component; and reactance (XC) was negatively correlated with the endomorphic component; both measurements were positively correlated with the ectomorphic component. The HD-negative correlations were observed between mass in water and the endomorphic and mesomorphic components, and positive correlations were observed with the ectomorphic component. Body volume and surface area were positively correlated with the endomorphic and mesomorphic components and negatively correlated with the ectomorphic component. Percent fat and fat weight were related to each of the three components of somatotype for males and females. Fat-free weight for males was also related to the mesomorphic and the ectomorphic components.     

Fat mass and fat-free mass as indicators of body composition among Bengalee Muslim children

Background: The composition of fat mass (FM) and fat-free mass (FFM) are now considered to be important indicators of body composition.

Aim: This cross-sectional study determines the body composition using FM and FFM among children.

Subjects and methods: The study was conducted among 1248 children (619 boys; 629 girls) aged 5–12 years and belonging to the Bengalee Muslim population of West Bengal, India. Anthropometric measurements of height, weight, triceps and sub-scapular skin-folds were recorded and body mass index (BMI) calculated. Body composition was assessed using FM and FFM.

Results: The age-specific mean values of FM and FFM ranged from 1.93–3.07 kg (boys) and 1.91–3.62 kg (girls) and from 14.69–23.44 kg (boys) and 14.18–22.87 kg (girls), respectively. Statistically significant sex differences were observed in FM and FFM (p < 0.05). Age- and sex-specific smooth percentile curves were derived for BMI, FM and FFM using the L, M and S modelling approach for further evaluation of body composition.

Conclusion: These findings are important for future investigations in the field and in epidemiological and clinical settings so as to accurately identify risk of lower or higher adiposity and body composition using FM and FFM.     

Multicompartment model of body composition assessment in Chinese-American adults

Using hydrodensitometry, dual energy x-ray absorptiometry, and deuterium dilution techniques, multiple compartment body composition assessment was performed on 29 adult Chinese-American men (n = 11) and women (n = 18). The purpose of the investigation was to determine if significant differences exist in the estimation of percentage of body fat (%BF) and fat-free mass (FFM), based on 2-, 3-, and 4-compartment models of body composition. Height, weight, and the body mass index (BMI) for the men were 170 cm, 63 kg, and 22 kg/m²; for the women, values were 161 cm, 59 kg, and 23 kg/m², respectively. Estimated values for %BF from density alone and density adjusted for TBW were not significantly different for either the men or women (20.5% vs. 18.8%) and (28.2% vs. 27.4%). However, %BF estimated from the 4-compartment model of density, TBW and BMC resulted in significantly lower values for both groups, 17.5% for men and 26.8% for women. The lack of a significant difference in %BF between density only and density adjusted for TBW indicates that TBW was within the accepted constancy value associated with hydrodensitometry. When density was adjusted for variation in both TBW and BMC, a significant decline occurred in the estimate of %BF for men, but not for women. The average TBW to FFM ratio was 0.75., 0.74, and 0.73 when using FFM values from 2-, 3-, and 4-compartment models, respectively. The average BMC to FFM ratio from two-, three-, and four-compartment estimates of FFM were 0.054, 0.053, and 0.052 for the men and 0.060, 0.059, and 0.059 for the women. The results suggest that Chinese-American men and women have similar TBW/FFM ratios, but the BMC/FFM ratio is higher in women than men. Am. J. Hum. Biol. 9:21–27 © 1997 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Assessment of total body potassium in healthy Italian men

BACKGROUND: Whole-body (40)K counting is a valuable tool for assessing cellular changes in body composition with ageing. AIM: The objectives of this study were to assess total body potassium (TBK) and body cell mass (BCM) differences with age, and to compare TBK and BCM between individuals with a body mass index (BMI) < 25 kg m(-2) versus > 25 kg m(-2). SUBJECTS AND METHODS: Body composition of 840 healthy Italian men, 18-70 years of age, was measured by whole-body counting of (40)K. BCM (kg) was calculated as 0.00833 x TBK (mmol). RESULTS: Body weight did not differ among groups. TBK, TBK/height, TBK/body weight, and BCM were significantly lower for the 51-70-year-old group compared with all other groups. The 51-70-year-old group with a BMI < 25 kg m(-2) had significantly lower TBK, TBK/height, and BCM than all other decades with a BMI < 25 kg m(-2); whereas TBK/body weight was significantly lower than the 18-30 and 31-40-year-old groups. The 51-70-year-old group with a BMI > 25 kg m(-2) had significantly lower TBK, TBK/height, TBK/body weight, and BCM than all other decades with a BMI > 25 kg m(-2). CONCLUSION: TBK and BCM decrease significantly with ageing, which could result in decreased functional capacity in older adults.     

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

Abstract

Background: Assessment of body composition plays a significant role in combating chronic disease among South Asians. Accurate assessment of body composition by bioelectrical impedance analysis (BIA) requires population-specific equations which are currently unavailable for urban South Asian women.

Aim: To assess validity of direct BIA assessment and selected equations for prediction of total body water (TBW), against Deuterium (²H₂O) dilution and develop and validate a population-specific TBW equation for urban South Asian women.

Subjects and method: Data of 80 urban Sri Lankan women (30–45 years) were used for this analysis. Body composition was assessed by ²H₂O dilution (reference) and BIA. Available BIA equations were assessed for validity. A new TBW equation was generated and validated.

Results: Direct BIA measurements and other equations did not meet validation criteria in predicting TBW. TBW by the new equation (TBW?=?3.443?+?0.342?×?(height²/impedance)?+?0.176?×?weight) correlated (p?<?0.001) with TBW by reference method. TBW using the new equation was not significantly different (25.30?±?2.4?kg) from the reference (25.32?±?2.7?kg).

Conclusion: Direct use of TBW by instrument and existing equations are less suitable for this population. The new TBW equation is suitable for body composition assessment in urban South Asian women.     

Proximal electrode placement improves the estimation of body composition in obese and lean elderly during segmental bioelectrical impedance analysis

Bioelectrical impedance analysis (BIA) is an affordable, non-invasive, easy-to-operate, and fast alternative method to assess body composition. However, BIA tends to overestimate the percent body fat (%BF) in lean elderly and underestimate %BF in obese elderly people. This study examined whether proximal electrode placement eliminates this problem. Forty-two elderly men and women (64–96 years) who had a wide range of BMI [22.4 ± 3.3 kg/m² (mean ± SD), range 16.8–33.9 kg/m²] and %BF (11.3–44.8%) participated in this study. Using ²H and ¹⁸O dilutions as the criterion for measuring total body water (TBW), we compared various BIA electrode placements; wrist-to-ankle, arm-to-arm, leg-to-leg, elbow-to-knee, five- and nine-segment models, and the combination of distal (wrists or ankles) and proximal (elbows or knees) electrodes. TBW was most strongly correlated with the square height divided by the impedance between the knees and elbows (H ²/Z _proximal; r = 0.965, P < 0.001). In the wrist-to-ankle, arm-to-arm, leg-to-leg, and five-segment models, we observed systematic errors associated with %BF (P < 0.05). After including the impedance ratio of the proximal to distal segments (P/D) as an independent variable, none of the BIA methods examined showed any systematic bias against %BF. In addition, all methods were able to estimate TBW more accurately (e.g., in the wrist-to-ankle model, from R ² = 0.90, SEE = 1.69 kg to R ² = 0.94, SEE = 1.30 kg). The results suggest that BIA using distal electrodes alone tends to overestimate TBW in obese and underestimate TBW in lean subjects, while proximal electrodes improve the accuracy of body composition measurements.     

Association of dominant somatotype of men with body structure,function during exercise,and nutritional assessment

This study examined the hypothesis that somatotype determines body structure, functional responses at peak exercise, and nutritional status of 63 men ages 18–40 years who lived under controlled conditions. Data were grouped by dominant somatotype to emphasize differences in body types. Dominant ectomorphs (n = 19) had less (P < 0.05) body weight, fat weight, and percent body fat than endomorphs (n = 14) and mesomorphs (n = 30). Fat-free weight (FFW), total body potassium (TBK), and body cell mass (BCM), normalized for stature, were lower (P < 0.05) in the ectomorphs than in the endomorphs and mesomorphs. Comparisons between measured and predicted FFW and TBK showed that only the ectomorphs had less (P < 0.05) FFW and TBK than expected. Although all groups had the same peak power output, the ectomorphs had different functional responses during peak exercise. Ectomorphs had the greatest respiratory exchange ratio (P < 0.05), ventilatory equivalent for oxygen, and end-exercise plasma lactate concentrations (P < 0.05), and lowest peak oxygen uptake (L/min; P < 0.05). Nutrient intakes and blood biochemical markers of nutritional status were within the range of normal values in all groups. Correlations between measures of body structure, function, and nutritional status and dominant somatotype components were calculated after controlling for the effects of the other two somatotype components. Partial correlations were variable, with significant correlations ranging from −0.30 to 0.87. These data indicate that ectomorphs, as compared to endomorphs and mesomorphs, have deficits in FFW and BCM which are associated with differences in functional capacity. Am. J. Hum. Biol. 12:167–180, 2000. Published 2000 Wiley-Liss, Inc.