Measurement of body fat in elderly subjects by dual-energy x-ray absorptiometry, bioelectrical impedance, and anthropometry

Body fat was measured in 46 elderly subjects by dual-energy x-ray absorptiometry [BF(DEXA)], bioelectrical impedance analysis (BIA), and anthropometry. Equations for prediction of the body fat (by DEXA) of elderly people by BIA and/or anthropometry were developed. The prediction of body fat (by DEXA) by anthropometric variables alone gave an r2 of 0.94 and the corresponding SEEs were 1.61 kg for men and 2.43 kg for women. When BIA variables were added as predictors, r2 increased by 2-5% (P less than 0.05) and the corresponding SEE decreased by 25% (P less than 0.05). The prediction of body fat (by DEXA) in elderly subjects and by BIA or anthropometry with equations developed in populations of young healthy adults (adapted from the literature) was generally not good although the correlation coefficients were high (r greater than 0.9, P less than 0.001), which suggests that our equations may improve prediction of body fat in elderly subjects.     

Determination of body composition in children with cerebral palsy: bioelectrical impedance analysis and anthropometry vs dual-energy x-ray absorptiometry

The object of this study was to determine whether bioelectrical impedance analysis (BIA) and anthropometry can be used to determine body composition for clinical and research purposes in children with cerebral palsy. Eight individuals with cerebral palsy (two female, mean age=10 years, mean gross motor function classification=4.6 [severe motor impairment]) recruited from an outpatient tertiary care setting underwent measurement of fat mass, fat-free mass, and percentage body fat using BIA, anthropometry (two and four skinfold equations), and dual-energy x-ray absorptiometry. Correlation coefficients were calculated for fat mass, fat-free mass, and percent body fat for these measures as determined by BIA and anthropometry when compared with dual-energy x-ray absorptiometry. Correlation coefficients were excellent for determination of fat-free mass for all methods (ie, all were above 0.9). Correlations were moderate for determination of fat mass and percent body fat (range=0.4 to 0.8).     

Body fat gain and loss differentially influence validity of dual-energy x-ray absorptiometry and multifrequency bioelectrical impedance analysis during simultaneous fat-free mass accretion

The validity of dual-energy x-ray absorptiometry (DXA) and multifrequency bioelectrical impedance analysis (MFBIA) for detecting changes in fat mass (FM), fat-free mass (FFM), and body fat percentage (BF%) was evaluated, as compared to a rapid 4-component (4C) model, in 31 females completing 8 weeks of resistance training. Analyses were performed in all participants (ALL) and in subgroups that gained FFM but lost FM (R subgroup) or gained both FFM and FM (G subgroup). It was hypothesized that methods would comparably detect changes in ALL, but discrepancies would occur in subgroup analysis. Changes in body composition did not significantly differ between 4C, DXA, and MFBIA. Equivalence testing indicated that similar changes were detected by DXA and MFBIA, compared to 4C, for ΔFFM in all analyses and ΔBF% in ALL and R subgroup. ΔFM was equivalent to 4C only in R subgroup for DXA and G subgroup for MFBIA. For ΔFM and ΔBF%, DXA and MFBIA produced similar magnitude errors in ALL. However, DXA exhibited lower error in R subgroup, whereas MFBIA exhibited lower error in G subgroup. For ΔFFM, DXA and MFBIA exhibited relatively similar errors in ALL and R subgroup, although MFBIA displayed proportional bias and weaker correlations with 4C than DXA. In G subgroup, MFBIA exhibited lower errors and a higher correlation with 4C ΔFFM than DXA. Although both DXA and MFBIA may have utility for estimating body composition changes during FFM accretion, DXA may be superior during simultaneous FM loss, whereas MFBIA may produce lower error during simultaneous FM gain.     

Body composition assessment of undernourished older subjects by dual-energy x-ray absorptiometry and bioelectric impedance analysis

Background  

The prevention and treatment of diseases related to changes in body composition require accurate methods for the measurement of body composition. However, few studies have dealt specifically with the assessment of body composition of undernourished older subjects by different methodologies.     

A comparison of skinfold thickness, body mass index, bioelectrical impedance analysis and dual-energy X-ray absorptiometry in assessing body composition in obese subjects before and after weight loss

The assessment of body composition in obese subjects by anthropometric means (skinfolds), presents many difficulties. This study compares the estimates provided of fat free mass in 21 obese subjects (mean body mass index 36.6 +/- 1.2 kg/m(2)) using body mass index and skinfold thickness, with those obtained using the more recently developed techniques of bioelectrical impedance analysis and dual-energy X-ray absorptiometry. Despite highly significant correlations between some of the methods (r(2) = 0.94 for dual-energy X-ray absorptiometry versus bioelectrical impedance analysis), there was a considerable lack of agreement in the measurements, particularly when skinfold thickness was compared with dual-energy X-ray absorptiometry (limits of agreement -21.9 to -1.5 kg for fat free mass estimated from dual-energy X-ray absorptiometry and skinfold thickness) and even for dual-energy X-ray absorptiometry and bioelectrical impedance analysis (limits of agreement -10.7 to 0.4 kg). After weight loss the intermethod differences were reduced.     

Body composition assessment in adults with cystic fibrosis: comparison of dual-energy X-ray absorptiometry with skinfolds and bioelectrical impedance analysis

OBJECTIVE: We compared body composition measurement in adults with cystic fibrosis (CF) by using non-invasive methods (skinfold thicknesses and bioelectrical impedance analysis [BIA]) with dual-energy X-ray absorptiometry (DXA). METHODS: Seventy-six adults with CF (mean age 29.9 +/- 7.9 y, mean body mass index 21.5 +/- 2.5 kg/m(2)) were studied. Body composition was measured to calculate fat-free mass (FFM) using DXA, the sum of four skinfold thicknesses, and BIA (predictive equations of Lukaski and of Segal). RESULTS: Mean FFM values +/- standard deviation measured using DXA were 54.8 +/- 7.3 kg in men and 41.2 +/- 3.9 kg in women. Mean FFM values measured using BIA/Lukaski were 51.5 +/- 7.8 kg in men and 40.4 +/- 4.9 kg in women (P < 0.0005 for men, not significant for women for comparison with DXA). Mean FFM values measured using BIA/Segal were 54.2 +/- 7.5 kg for men and 44.1 +/- 5.9 kg for women (not significant for men, P < 0.0005 for women for comparison with DXA). Mean FFM values measured using skinfolds were significantly higher than those for FFM with DXA (57.2 +/- 7.2 kg in men, 43.3 +/- 4.3 kg in women, P < 0.0005 for comparison with DXA). The 95% limits of agreement with FFM using DXA were, for men and women, respectively, -8.3 to 1.7 kg and -6.4 to 4.8 kg for BIA/Lukaski, -4.8 to 3.6 kg and -3.1 to 8.9 kg for BIA/Segal, and -2.8 to 7.3 kg and -1.5 to 5.7 kg for skinfolds. CONCLUSION: This study suggests that skinfold thickness measurements and BIA will incorrectly estimate FFM in many adults with CF compared with DXA measurements of FFM. These methods have limited application in the assessment of body composition in individual adult patients with CF.     

Proportional bias between dual-energy x-ray absorptiometry and bioelectrical impedance analysis varies based on sex in active adults consuming high- and low-carbohydrate diets

Dual-energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) are common methods of body composition assessment, but the agreement between these methods varies. Bias between DXA and single-frequency BIA was evaluated at 6 different time points in 48 active male and female adults consuming standardized high- and low-carbohydrate diets. It was hypothesized that fixed and proportional biases exist between DXA and BIA but that the extent of bias does not differ based on sex. Substantial fixed bias was present for estimates obtained by DXA and BIA, and both men and women exhibited proportional bias for fat mass (FM) and fat-free mass (FFM). The magnitude of bias was greater in women, and only women exhibited proportional bias for body fat percentage. In individuals with less FM, the mean difference between DXA and BIA was high, indicating that BIA underestimated FM relative to DXA. However, in individuals with greater FM, better agreement was seen. Correspondingly, the mean difference in FFM estimates was greater in individuals with less FFM. In some individuals with high quantities of FM or FFM relative to the sample, the relationship between devices was reversed such that BIA overestimated FM and underestimated FFM. The degree of disagreement between DXA and BIA varies substantially based on body size and sex such that all-encompassing statements regarding the comparability of these technologies cannot presently be made.     

Estimation of body fat mass using dual-energy x-ray absorptiometry, bioelectric impedance analysis, and anthropometry in HIV-positive male subjects receiving highly active antiretroviral therapy

BACKGROUND: The purpose of this pilot study was to compare estimates of percentage body fat mass (FM) by bioelectric impedance analysis (BIA) and skinfold measurements (SF) with estimates obtained from dual-energy x-ray absorptiometry (DEXA) in 47 HIV-infected male subjects receiving highly active antiretroviral therapy (HAART). As different patterns of abdominal fat accumulation might affect the body FM estimation, correlation and agreement of these methods were also compared in patients with waist to hip ratio (WHR) < or =0.9 and >0.9. METHODS: Body FM was estimated by BIA and by measuring skinfold thickness at biceps, triceps, and subscapular area, and was compared with DEXA as the reference method using paired t-test. RESULTS: Estimates by SF were significantly higher and by BIA were significantly lower compared with DEXA for all subjects. This relationship persisted only in those with WHR >0.9. Both BIA and SF correlated significantly with DEXA, but they did not agree. However, both techniques showed a small intermethod bias, and the precision was within the acceptable range. This relationship persisted in those with WHR >0.9. In comparison with measurement by BIA, SF showed poorer agreement (larger bias and error). Conclusion: For population studies and perhaps to monitor changes over time for intervention studies, the bias for both BIA and SF methods is relatively small and errors and precisions are within the acceptable range when compared with DEXA, and thus all 3 techniques can be used for routine monitoring of total body FM in male subjects with HIV infection.     

Utility of multifrequency bioelectrical impedance compared with dual-energy x-ray absorptiometry for assessment of total and regional body composition varies between men and women

Multifrequency bioelectrical impedance analysis of body composition may be an appropriate alternative to dual-energy x-ray absorptiometry. We hypothesized that there would be no significant differences between dual-energy x-ray absorptiometry and either the Biospace (Los Angeles, CA, USA) InBody 520 or 720 multifrequency bioelectrical impedance analysis devices for total lean body mass (LBM), appendicular lean mass (ALM), trunk lean mass (TM), and total fat mass (FM) in 25 men and 25 women (including lean, healthy, and obese individuals according to body mass index), age 18 to 49 years, weight of 73.6 ± 15.4 kg. Both devices overestimated LBM in women (~ 2.5 kg, P < .001) and underestimated ALM in men (~ 3.0 kg, P < .05) and women (~ 1.0 kg, P < .05). The 720 overestimated FM in men (1.6 kg, P < .05) and underestimated TM in women (0.6 kg, P ≤ .05). Regression analyses in men revealed R² (0.87-0.91), standard error of the estimate (SEE; 2.3-2.8 kg), and limits of agreement (LOAs; 4.5-5.7 kg) for LBM; R² (0.62-0.87), SEE (1.5-2.6 kg), and LOA (3.2-6.0 kg) for ALM; R² (0.52-0.71), SEE (2.4-3.0 kg), and LOA (4.6-6.1 kg) for TM; and R² (0.87-0.93), SEE (1.9-2.6 kg), and LOA (5.9-6.2 kg) for FM. Regression analyses in women revealed R² (0.87-0.88), SEE (1.8-1.9 kg), and LOA (4.1-4.2 kg) for LBM; R² (0.78-0.79), SEE (1.4-1.5 kg), and LOA (2.7-2.9 kg) for ALM; R² (0.76-0.77), SEE (1.0 kg), and LOA (2.2-2.3 kg) for TM; and R² (0.95), SEE (2.2 kg), and LOA (4.3-4.4 kg) for FM. The InBody 520 and 720 are valid estimators of LBM and FM in men and of LBM, ALM, and FM in women; the 720 and 520 are valid estimators of TM in men and women, respectively.     

Migration of the bioelectrical impedance vector in healthy elderly subjects

OBJECTIVE: We describe the effects of aging on the bioelectrical impedance vectors in healthy men and women. METHODS: Resistance (R) and reactance (Xc; standard, tetrapolar analysis at 50-kHz frequency) were measured in 201 volunteers (97 men and 104 women) aged 60 to 89 y. Criteria of exclusion from the sample were hospitalization within 3 mo before the survey, current medical treatment, physical handicaps, or other pathologies that might influence the measurements. Stature, weight, and four body circumferences were also measured, and body mass index was calculated. The values of R and Xc were normalized for stature (H) and adjusted for body circumferences by means of covariance analysis. Age- and sex-dependent bioelectrical changes were evaluated by two-factor analysis of variance and Hotelling's T(2) test. RESULTS: The bioelectrical data of the sample agreed well with the normal reference values of the Italian population. R/H showed a significant increase with age in both sexes, whereas Xc/H and the phase angle significantly decreased. The greatest changes occurred in the 70- to 79-y to the 80- to 89-y groups. After adjustment of the bioelectrical values for body circumferences, only Xc/H and the phase angle showed significant differences that decreased with age. CONCLUSIONS: The impedance vectors of healthy individuals showed a clear trend in the elderly, in both sexes, and particularly after age 80 y. The bioelectrical parameters indicated a reduction of soft tissue mass with age, as they tended to approach values typical of pathologically lean subjects (cachetic and anorexic states). After adjustment for the circumferences, the changes in the vector concerned only the Xc component, a measure of the capacitance produced by cell membranes of soft tissues. Therefore, in addition to the quantitative change, the electrical properties of the tissues may also change.     

双能X线吸收法和生物电阻抗法测量成年超重和肥胖人群骨矿含量的一致性分析

目的分析生物电阻抗法(MF-BIA)和双能X线吸收法(DXA)测量成年超重、肥胖人群骨矿含量的一致性,建立MF-BIA法校正预测模型,为MF-BIA法准确测量我国成年超重、肥胖人群的骨矿含量提供依据。方法志愿招募成年超重、肥胖者1323人,分别采用MF-BIA法和DXA法测定受试者的骨矿含量,分析2种方法测量结果的一致性,并建立MF-BIA法校正预测模型。结果 MF-BIA法测量成年超重男性、肥胖男性、超重女性、肥胖女性的骨矿含量与DXA法测量的骨矿含量差值分别为0.28、0.38、0.24和0.36 kg,差异均有统计学意义(P0.05)。成年超重男性、肥胖男性、超重女性、肥胖女性MF-BIA法与DXA法测量骨矿含量的组内相关系数(ICC)分别为0.787、0.796、0.741和0.788,均有统计学意义(P0.01)。MF-BIA法校正预测模型为:超重男性人群,骨矿含量(DXA法)=-0.297+1.005×骨矿含量(MF-BIA法);肥胖男性人群,骨矿含量(DXA法)=0.302+0.799×骨矿含量(MF-BIA法);超重女性人群,骨矿含量(DXA法)=0.780+0.598×骨矿含量(MF-BIA法);肥胖女性人群,骨矿含量(DXA法)=0.755+0.597×骨矿含量(MF-BIA法)。结论 MF-BIA法和DXA法测量中国成年超重、肥胖人群骨矿含量一致性较差;在中国成年超重、肥胖人群中,使用MFBIA法测量骨矿含量需进行校正。     

Body composition by X-ray absorptiometry and bioelectrical impedance in chronic respiratory insufficiency patients

Nutrition assessment is important during chronic respiratory insufficiency to evaluate the level of malnutrition or obesity and should include body composition measurements. The appreciation of fat-free and fat reserves in patients with chronic respiratory insufficiency can aid in designing an adapted nutritional support, e.g., nutritional support in malnutrition and food restriction in obesity. The purpose of the present study was to cross-validate fat-free and fat mass obtained by various bioelectric impedance (BIA) formulas with the fat-free and fat mass measured by dual-energy X-ray absorptiometry (DXA) and determine the formulas that are best suited to predict the fat-free and fat mass for a group of patients with severe chronic respiratory insufficiency. Seventy-five patients (15 women and 60 men) with chronic obstructive and restrictive respiratory insufficiency aged 45–86 y were included in this study. Body composition was calculated according to 13 different BIA formulas for women and 12 for men and compared with DXA. Because of the variability, calculated as 2 standard deviations, of ± 5.0 kg fat-free mass for women and ± 6.4 kg for men for the best predictive formula, the use of the various existing BIA formulas was considered not clinically relevant. Therefore disease-specific formulas for patients with chronic respiratory insufficiency should be developed to improve the prediction of fat-free and fat mass by BIA in these patients.     

Fat-free and fat mass percentiles in 5225 healthy subjects aged 15 to 98 years.

OBJECTIVES: Fat-free mass (FFM) and fat mass (FM) are important in the evaluation of nutritional status. Bioelectrical impedance analysis (BIA) is a simple, reproducible method used to determine FFM and FM. Because normal values for FFM and FM have not yet been established in adults aged 15 to 98 y, its use is limited in the evaluation of nutritional status. The aims of this study were to determine reference values for FFM, FM, and percentage of FM by BIA in a white population of healthy adults, observe their differences with age, and develop percentile distributions for these parameters between ages 15 and 98 y. METHODS: Whole-body resistance and reactance of 2735 healthy white men and 2490 healthy white women, aged 15 to 98 y, was determined by 50-kHz BIA, with four skin electrodes on the right hand and foot. FFM and FM were calculated by a previously validated, single BIA formula and analyzed for age decades. RESULTS: Mean FFM peaked in 35- to 44-y-old men and 45- to 54-y-old women and declined thereafter. Mean FFM was 8.9 kg or 14.8% lower in men older than 85 y than in men 35 to 44 y old and 6.2 kg or 14.3% lower in women older than 85 y than in women 45 to 54 y old. Mean FM and percentage of FM increased progressively in men and women between ages 15 and 98 y. The results suggested that the greater weight noted in older subjects is due to larger FM. CONCLUSIONS: The percentile data presented serve as reference to evaluate deviations from normal values of FFM and FM in healthy adult men and women at a given age.     

Comparison of bioelectrical impedance analysis and dual-energy X-ray absorptiometry for the assessment of appendicular body composition in anorexic women

OBJECTIVE: To establish the accuracy of bioelectrical impedance analysis (BIA) for the assessment of appendicular body composition in anorexic women. DESIGN: Cross-sectional study. SETTING: Outpatient University Clinic. SUBJECTS: A total of 39 anorexic and 25 control women with a mean (s.d.) age of 21 (3) y. METHODS: Total, arm and leg fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry and predicted from total and segmental BIA at 50 kHz. The predictor variable was the resistance index (Rl), that is, the ratio of height (2) to body resistance for the whole body and the ratio of length(2)/limb resistance for the arm and leg. RESULTS: Predictive equations developed on controls overestimated total, arm and leg FFM in anorexics (P<0.0001). Population-specific equations gave a satisfactory estimate of total and appendicular FFM in anorexics (P=NS) but had higher percent root mean square errors (RMSEs%) as compared to those developed on controls (8% vs 5% for whole body, 12% vs 10% for arm and 10% vs 8% for leg). The accuracy of the estimate of total and leg FFM in anorexics was improved by adding body weight (Wt) as a predictor with Rl (RMSE%=5% vs 8% and 7% vs 10%, respectively). However, the same accuracy was obtained using Wt alone, suggesting that in anorexics, BIA at 50 kHz is not superior to Wt for assessing total and leg FFM. CONCLUSION: BIA shows some potential for the assessment of appendicular body composition in anorexic women. However, Wt is preferable to BIA at 50 kHz on practical grounds. Further studies should consider whether frequencies >50 kHz give better estimates of appendicular composition in anorexics as compared to Wt. SPONSORSHIP: University of Napoli.     

Evaluation of body composition using dual-energy X-ray absorptiometry, skinfold thickness and bioelectrical impedance analysis in Japanese female college students

We compared three methods for evaluating body composition: dual-energy X-ray absorptiometry (DXA), skinfold thickness (Skinfolds), and bioelectrical impedance analysis (BIA). Subjects were 155 healthy young college-aged Japanese females whose mean+/-SD (range) age, body height, body weight and body mass index (BMI) were 20.1+/-0.3 (19.6-21.1) y, 158.9+/-4.7 (145.4-172.6) cm, 52.0+/-6.8 (39.4-84.6) kg and 20.6+/-2.3 (16.5-32.5), respectively. Their mean skinfold thickness at the triceps and subscapular were 16.9+/-4.7 (8.0-31.0) and 16.0+/-5.7 (7.0-40.0) mm, respectively. Mean body fat mass percentages evaluated by DXA, Skinfolds and BIA were 29.6+/-5.1, 22.8+/- 5.3 and 25.8+/-4.7%, respectively. Body fat mass was 15.4+/-4.4, 12.1+/-4.5 and 13.6+/-4.5 kg, respectively. Simple correlation coefficients between the three methods for body fat mass percentages provided the following coefficients: r=0.741 for DXA vs. Skinfolds, r=0.792 for DXA vs. BIA and r=0.781 for Skinfolds vs. BIA. Simple correlation coefficients for body fat mass were as follows: r=0.898 for DXA vs. Skinfolds, r=0.927 for DXA vs. BIA and r=0.910 for Skinfolds vs. BIA (all p<0.001). There were significant differences in the values among the three methods with the Skinfolds providing the lowest body fat mass and percentage, and DXA the highest (p<0.001). They all appear to be strongly correlated for evaluating body composition: however, different cut-off values for defining obese and lean need to be defined for each method.