Are Ethnic and Gender Specific Equations Needed to Derive Fat Free Mass from Bioelectrical Impedance in Children of South Asian, Black African-Caribbean and White European Origin? Results of the Assessment of Body Composition in Children Study

Background Bioelectrical impedance analysis (BIA) is a potentially valuable method for assessing lean mass and body fat levels in children from different ethnic groups. We examined the need for ethnic- and gender-specific equations for estimating fat free mass (FFM) from BIA in children from different ethnic groups and examined their effects on the assessment of ethnic differences in body fat. Methods Cross-sectional study of children aged 8–10 years in London Primary schools including 325 South Asians, 250 black African-Caribbeans and 289 white Europeans with measurements of height, weight and arm-leg impedance (Z; Bodystat 1500). Total body water was estimated from deuterium dilution and converted to FFM. Multilevel models were used to derive three types of equation {A: FFM = linear combination(height+weight+Z); B: FFM = linear combination(height2/Z); C: FFM = linear combination(height2/Z+weight)}. Results Ethnicity and gender were important predictors of FFM and improved model fit in all equations. The models of best fit were ethnicity and gender specific versions of equation A, followed by equation C; these provided accurate assessments of ethnic differences in FFM and FM. In contrast, the use of generic equations led to underestimation of both the negative South Asian-white European FFM difference and the positive black African-Caribbean-white European FFM difference (by 0.53 kg and by 0.73 kg respectively for equation A). The use of generic equations underestimated the positive South Asian-white European difference in fat mass (FM) and overestimated the positive black African-Caribbean-white European difference in FM (by 4.7% and 10.1% respectively for equation A). Consistent results were observed when the equations were applied to a large external data set. Conclusions Ethnic- and gender-specific equations for predicting FFM from BIA provide better estimates of ethnic differences in FFM and FM in children, while generic equations can misrepresent these ethnic differences

Body fat measurement among Singaporean Chinese, Malays and Indians: a comparative study using a four-compartment model and different two-compartment models

This cross-sectional study compared body fat percentage (BF€obtained from a four-compartment (4C) model with BF␏rom hydrometry (using 2H2O), dual-energy X-ray absorptiometry (DXA) and densitometry among the three main ethnic groups (Chinese, Malays and Indians) in Singapore, and determined the suitability of two-compartment (2C) models as surrogate methods for assessing BFmong different ethnic groups. A total of 291 subjects (108 Chinese, seventy-six Malays, 107 Indians) were selected to ensure an adequate representation of age range (18-75 years) and BMI range (16-40 kg/m2) of the general adult population, with almost equal numbers from each gender group. Body weight was measured, together with body height, total body water by 2H2O dilution, densitometry with Bodpod? and bone mineral content with Hologic? QDR-4500. BF␖easurements with a 4C model for the subgroups were: Chinese females 33?5 (SD 7?5), CHINESE MALES 24?4 (sd 6?1), Malay females 37?8 (sd 6?3), Malay males 26?0 (sd 7?6), Indian females 38?2 (sd 7?0), Indian males 28?1 (sd 5?5). Differences between BF␖easured by the 4C and 2C models (hydrometry, DXA and densitometry) were found, with underestimation of BF␒n all the ethnic-gender groups by DXA of 2?1-4?2 BFnd by densitometry of 0?5-3?2 BFŽ On a group level, the differences in BF␋etween the 4C model and 2H2O were the lowest (0?0-1?4 BF␒n the different groups), while differences between the 4C model and DXA were the highest. Differences between the 4C model and 2H2O and between the 4C model and DXA were positively correlated with the 4C model, water fraction (fwater) of fat-free mass (FFM) and the mineral fraction (fmineral) of FFM, and negatively correlated with density of the FFM (DFFM), while the difference between 4C model and densitometry correlated with these variables negatively and positively respectively (i.e. the correlations were opposite). The largest contributors to the observed differences were fwater and DFFM. When validated against the reference 4C model, 2C models were found to be unsuitable for accurate measurements of BFt the individual level, owing to the high errors and violation of assumptions of constant hydration of FFM and DFFM among the ethnic groups. On a group level, the best 2C model for measuring BFmong Singaporeans was found to be 2H2O

Ethnic Differences in Body Composition and Obesity Related Risk Factors: Study in Chinese and White Males Living in China

The purpose of this cross-sectional observational study was to identify ethnic differences in body composition and obesity-related risk factors between Chinese and white males living in China. 115 Chinese and 114 white male pilots aged 28–63 years were recruited. Fasting body weight, height and blood pressure were measured following standard procedures. Whole-body and segmental body composition were measured using an 8-contact electrode bioimpedance analysis (BIA) system. Fasting serum glucose, fasting plasma total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, and triglycerides (TG) were assessed using automatic biochemistry analyzer. After adjusting for age and body mass index (BMI), Chinese males had significantly higher percentage of body fat (PBF) both with respect to whole body (Chinese: 23.7%±0.2% vs. Whites: 22.4%±0.2%) and the trunk area (Chinese: 25.0%±0.3% vs. Whites: 23.2%±0.3%) compared to their white counterparts. At all BMIs, Chinese males had significantly higher fasting glucose levels (Chinese: 5.7±1.0 mmol/L vs. Whites: 5.2±1.0 mmol/L) but lower high-density lipoprotein levels (Chinese: 0.8±1.0 mmol/L vs. Whites: 1.0±1.0 mmol/L) than white males. In addition, a marginally significantly higher diastolic blood pressure was found among Chinese men than that among white men (Chinese: 80±1.0 mmHg vs. Whites: 77±1.0 mmHg). Chinese males had more body fat and a greater degree of central fat deposition pattern than that seen in white males in the present study. Furthermore, data on blood pressure, fasting glucose and blood lipids suggest that Chinese men may be more prone to obesity-related risk factors than white men

BMI and Diabetes Risk in Singaporean Chinese

10.2337/dc08-1674Diabetes Care3261104-1106DICA

Body mass index as a measure of body fatness: age- and sex-specific prediction formulas

In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9-40.9 kg/m2), and an age range of 7-83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males = 1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51 x BMI-0.70 x age - 3.6 x sex + 1.4 (R2 0.38, SE of estimate (SEE) 4.4% BF%). In adults the prediction formula was: BF% = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (R2 0.79, SEE = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance

Comparative study of the relationship between multi-frequency impedance and body water compartments in two European populations

To investigate possible differences in the relationship between multi-frequency impedance and body-water compartments (total body water (TBW) and extracellular water (ECW)) measured by dilution techniques in two European populations, we studied forty Italian (twenty male and twenty female) and forty-three Dutch (twenty-three male and twenty female) healthy subjects aged 19-41 years. The main differences in body build between the two groups were height, trunk length and the two ratios TBW/height and ECW/height. Population-specific prediction formulas for ECW (at 1 kHz) and TBW (at 100 kHz) were developed. The prediction errors for ECW and TBW were about 0.6 and 1.5 kg respectively, (CV 4%) in both groups. Cross-validation analysis showed no significant error in the prediction of TBW but a slight error (range -4.9 to +2.8%) in the ECW prediction. The biases in both TBW and ECW were correlated with ECW/TBW (r -0.44, P < 0.0005 and r +0.52, P < 0.0005 respectively) in the two groups; the biases in ECW were also related to ECW/height (r 0.51, P < 0.001), TBW/height (r 0.25, P < 0.05), trunk length (r 0.36, P < 0.001) and Z1/Z100 (r 0.32, P < 0.01). In conclusion, the water distribution between the extra- and intracellular compartments emerged in the present study as the major cause of error in the prediction of body water, and in particular of ECW from impedance measurements with a population-specific equation. Moreover, body build, expressed as TBW/height and ECW/height, had an impact on the bias

Body fatness, relative weight and frame size in young adults

1. Body-weight, body height, knee width, wrist width and skinfold measurements were made on males (n 139) and females (n 167) in three age-groups (20–22, 25–27 and 30–32 years). Percentage of body fal was calculated from skinfold thicknesses using regression equations according to Durnin & Womersley (1974), Three indices of relative weight were calculated: W/H2, W/Hp and W/Ŵ, where W is body-weight, H is body height, p is the exponent that made the index of relative weight independent of height and W is the weight, estimated from body height and frame size. 2. The standard error of the estimate of body-weight was only reduced by 5% in males and by 13% in females when, in addition to body height, knee width was taken into account.The addition of wrist width did not improve the accuracy of estimation of body-weight in either sex. Therefore in further analyses W was estimated from body height and knee width. In the present population the exponent p was 1·7 in males and 1·6 in females. 3. The correlations between the percentage of body fat and the indices, W/H2, W/HP, and W/Ŵ, were all very similar, being approximately 0·8 in both sexes. 4. A positive relationship was observed between percentage of body fat and knee width in females, which may be explained by an artifact of measurement. 5. In conclusion it can be stated that the accuracy of estimation of percentage of body fat was not improved when the index of relative weight was adjusted for knee width or wrist width in the present population. The W/H2was the most preferable of the three indices which were calculated