Assessment of postpartum body fat change from underwater weight and skinfold thickness measurements

Postpartum body fat change was monitored in 11 women using hydrostatic (underwater) weight (UWW) and a combination of triceps, subscapular, and suprailiac skinfold measurements. Overall mean percent body fat (PBF) estimates from UWW and the skinfold sum did not differ. Multiple regression analysis demonstrated that 82.2% of the variance in the UWW estimate of PBF was explained by a linear combination of the triceps, subscapular, and suprailiac estimates (P<0.01). Simple linear regression models indicated that the suprailiac estimate of PBF was the best single predictor of UWW PBF (P<0.001) explaining nearly as much of the variance as the linear combination of the 3 sites. Results suggest that skinfold thickness measurements can serve as a useful clinical tool for monitoring body fat change in the postpartum female under specific conditions.     

A comparison of dual-energy X-ray absorptiometry and somatometrics for determining body fat in rhesus macaques

OBJECTIVE: Various approaches have been used to assess fat and fat distribution in nonhuman primates, including measurements of body weight, body dimensions, and estimates derived from these, such as body mass index. Methods such as tritiated water dilution and dual-energy X-ray absorptiometry (DXA) have also been used. The aim of the present study was to evaluate and compare DXA measurements and somatometrics. RESEARCH METHODS AND PROCEDURES: Body composition of 15 adult male rhesus macaques was measured by DXA and somatometrics at four time-points over a 4-year period. Additionally, DXA precision and somatometric variability were analyzed by repeated measurements of the same subjects. RESULTS: DXA estimates of body fat were positively correlated with body weight, body mass index, body circumferences, and abdominal skinfold thicknesses. DXA assessments of soft tissue composition were precise, with coefficients of variation below 3.3% for all compartments analyzed. The majority of the observed variability in somatometrics was explained by subject variance, rather than by inter- or intraobserver variability, or by observer experience level. DISCUSSION: We conclude that noninvasive DXA technology provides precise estimates of nonhuman primate body composition that correlate well with the traditional somatometric measures used in primate studies.     

Body fat measurement in adolescents: comparison of skinfold thickness equations with dual-energy X-ray absorptiometry

OBJECTIVE: To compare the most commonly used equations to predict body fatness from skinfold thickness, in male and female adolescents, with dual-energy X-ray absorptiometry (DXA) as a reference method of fatness measurement. DESIGN: Cross-sectional nutrition survey. SETTING: General adolescent population from Zaragoza (Spain). SUBJECTS AND METHODS: A total of 238 Caucasian adolescents (167 females and 113 males), aged 13.0-17.9 y, were recruited from 15 school groups in 11 public and private schools. The percentage fat mass (%FM) was calculated by using skinfold-thickness equations. Predicted %FM was compared with the reference %FM values, measured by DXA. The lack of agreement between methods was assessed by calculating the bias and its 95% limits of agreement. RESULTS: Most equations did not demonstrate good agreement compared with DXA. However, in male adolescents, Slaughter et al equations showed relative biases that were not dependent on body fatness and the limits of agreement were narrower than those obtained from the rest of equations. In females, Brook's equation showed nonsignificant differences against DXA and the narrowest 95% limits of agreement. Only biases from Brook and Slaughter et al equations were not dependent on body fatness in female adolescents. CONCLUSIONS: Accuracy of most of the skinfold-thickness equations for assessment of %FM in adolescents was poor at the individual level. Nevertheless, to predict %FM when a relative index of fatness is required in field or clinical studies, Slaughter et al equations may be used in adolescents from both sexes and the Brook equation in female adolescents.     

Multiple imputation of missing dual-energy X-ray absorptiometry data in the National Health and Nutrition Examination Survey

In 1999, dual-energy x-ray absorptiometry (DXA) scans were added to the National Health and Nutrition Examination Survey (NHANES) to provide information on soft tissue composition and bone mineral content. However, in 1999-2004, DXA data were missing in whole or in part for about 21 per cent of the NHANES participants eligible for the DXA examination; and the missingness is associated with important characteristics such as body mass index and age. To handle this missing-data problem, multiple imputation of the missing DXA data was performed. Several features made the project interesting and challenging statistically, including the relationship between missingness on the DXA measures and the values of other variables; the highly multivariate nature of the variables being imputed; the need to transform the DXA variables during the imputation process; the desire to use a large number of non-DXA predictors, many of which had small amounts of missing data themselves, in the imputation models; the use of lower bounds in the imputation procedure; and relationships between the DXA variables and other variables, which helped both in creating and evaluating the imputations. This paper describes the imputation models, methods, and evaluations for this publicly available data resource and demonstrates properties of the imputations via examples of analyses of the data. The analyses suggest that imputation helps to correct biases that occur in estimates based on the data without imputation, and that it helps to increase the precision of estimates as well. Moreover, multiple imputation usually yields larger estimated standard errors than those obtained with single imputation.     

A 360-degree overview of body composition in healthy people: Relationships among anthropometry,ultrasonography, and dual-energy x-ray absorptiometry

ObjectiveThe aim of this study was to test the relationship between anthropometry, ultrasonography, and dual-energy x-ray absorptiometry (DXA) for the assessment of body composition in clinical practice.MethodsThe study was carried out in Italian blood donor volunteers belonging to five different age groups (18–70 y old; 25 men and 25 women per group; N = 250 participants; n = 125 men, n = 125 women). A complete history was collected and routine blood analyses were performed to confirm healthy status. All participants were submitted to whole-body DXA (tricompartmental analysis, regional, and total body), ultrasonography (abdominal adiposity evaluation), and anthropometric measurements. DXA was used as gold standard and its biomarkers were taken as reference for fat–lean mass balance, central–peripheral fat distribution, central or visceral fat, and subcutaneous fat.ResultsAnthropometric and ultrasound parameters were closely associated with most of DXA parameters. Composite markers representative of central and abdominal visceral fat compartments were significantly correlated with waist circumference, waist-to-hip ratio, and intra-abdominal fat thickness by ultrasound, in both men and women (P < 0.025). As expected, subcutaneous depots were significantly correlated with maximum subcutaneous fat thickness measured by ultrasonography (P < 0.025).ConclusionsBoth anthropometry and ultrasonography provide a reliable estimate of visceral adipose tissue in a non-obese population compared with DXA, whereas anthropometry prediction of subcutaneous adiposity is weak. Physicians should be aware of the limits of these techniques for the assessment of body composition.     

Body fat in neonates and young infants: validation of skinfold thickness versus dual-energy X-ray absorptiometry

BACKGROUND: There is an interest in noninvasive measurement of body fat in newborns and infants. Measurement of skinfold thickness (SFT) is a simple clinical method. OBJECTIVE: We correlated fat mass (FM) values of neonates and infants predicted from SFT measurements and compared them with FM values measured by dual-energy X-ray absorptiometry (DXA), a validated in vivo method for determining body fat. DESIGN: The weight, length, body composition (DXA measurement of FM and percentage of body fat), and SFT of 104 healthy term and preterm infants were measured at 0, 2, and 4 mo of age. RESULTS: Mean (+/- SD) FM determined by DXA increased from 440 +/- 220 g at birth to 1310 +/- 450 g at 2 mo of age and to 2170 +/- 605 g at 4 mo of age. The percentage of body fat increased from 13.3% at birth to 24.5% and 31.2% at 2 and 4 mo of age, respectively. An equation was developed to calculate FM (in g) in newborns by using the sum of SFT measurements (in mm) and body length (l; in cm): FM = 68.2 x SigmaSFT((0.0162) x l) - 172.8 (R(2) = 0.948, P < 0.001). CONCLUSIONS: With the use of statistical bootstrap analysis, the results provide an in vivo validation of SFT measurements against DXA for newborns and young infants. Body fat measurements by SFT correlate with FM values determined by DXA (R(2) = 0.936). Estimation of nutritional status is possible with errors (SD) of +/- 75, +/- 170, +/- 300, and +/- 380 g for infants with an FM 2000 g, respectively.     

Fundamental movement skill proficiency and body composition measured by dual energy X-ray absorptiometry in eight-year-old children

Objective: The main aim was to examine the association between fundamental movement skills (FMS) and objectively measured body composition using dual energy X-ray absorptiometry (DXA). Methods: A study of 304 eight-year-old children in Finland. FMS were assessed with the Test of gross motor development, 2nd ed. Total body fat percentage (BF%), abdominal region fat percentage (AF%) and fat-free mass (FFM) were assessed by DXA. Waist circumference, height and weight were measured, and International Obesity Task Force cut-off values for body mass index were used for the definition of healthy weight and overweight/obesity. Results: Better FMS proficiency (object control, locomotor and total FMS) was significantly and strongly associated with lower BF% and lower AF% measured with DXA. Conclusions: The inverse association between FMS and body composition measured with DXA (BF% and AF%) is an important finding, as body fatness and specifically abdominal fatness are associated with less favourable cardiovascular risk factor status in children.     

双能X线吸收法和生物电阻抗法测量成年超重/肥胖人群体脂率一致性分析

目的 分析生物电阻抗(MF-BIA)法和双能X线吸收(DXA)法测量成年超重/肥胖人群体脂率的一致性,并建立MF-BIA法校正预测模型。方法 招募志愿成年超重/肥胖者1 323人,分别采用MF-BIA法和DXA法测定受试者的体脂率,分析两方法测量结果的一致性,并建立MF-BIA法校正预测模型。结果 成年男女性超重/肥胖的MF-BIA法与DXA法测量体脂率差值分别为-6.5%、-4.3%和-2.5%、0.5%,差异均有统计学意义(均P<0.01),其体脂率的组内相关系数分别为0.746、0.807和0.628、0.674,差异均有统计学意义(均P<0.01)。MF-BIA法校正预测模型包括超重男性人群:体脂率(DXA法)=13.425+0.719×体脂率(MF-BIA法);肥胖男性人群:体脂率(DXA法)=12.572+0.741×体脂率(MF-BIA法);超重女性人群:体脂率(DXA法)=9.785+0.802×体脂率(MF-BIA法);肥胖女性人群:体脂率(DXA法)=20.348+0.532×体脂率(MF-BIA法)。结论 MF-BIA法和DXA法测量我国成年超重/肥胖人群体脂率一致性较差,使用MF-BIA法测量体脂率需进行校正。     

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.     

Estimations of body fat by anthropometry or bioelectrical impedance differ from those by dual-energy X-ray absorptiometry in prefrail community-dwelling older women

This study aimed to compare different methods to assess body fat (BF). We hypothesized that bioelectrical impedance analysis (BIA) or anthropometry may be used to estimate BF in prefrail older women, equivalently to dual-energy X-ray absorptiometry (DXA). The cross-sectional study included 72 prefrail community-dwelling older women (71.13 ± 4.65 years old; body mass index [BMI] 28.89 ± 4.23 kg/m²). The BF percentage (%BF) was estimated using anthropometry with the Durnin & Womersley (D&W) and Petroski's predictive equations, BIA with 2 Baumgartner predictive equations (BIA 1 and BIA 2), and DXA. All methods differed significantly from DXA according to assessments using repeated measures ANOVA and pairwise comparisons. The mean %BF varied between 39.99 ± 3.42% (D&W) and 43.93 ± 5.06% (DXA). Multiple regression analysis with age and BMI as covariates showed positive correlations (R² = 0.91) in models with D&W equation and BMI, and with BIA 2 and BMI; however, BMI explained more of the model (71%) than the equations. Furthermore, Bland-Altman test revealed a proportional bias for D&W and for BIA 2, with underestimation of BF varying across different %BF values. Petroski's skinfold equation showed a positive correlation on linear regression (R² = 0.74) and no proportional bias; however, Bland-Altman analysis revealed high limits of agreement (-13.6 to -0.05), thus compromising clinical application. To conclude, compared with DXA, all the equations tested showed a high disagreement and wide limits of agreement, restricting their use in clinical practice to estimate the BF in prefrail older women.     

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.     

Estimates of percentage body fat in young adolescents: a comparison of dual-energy X-ray absorptiometry and air displacement plethysmography

OBJECTIVE: To evaluate the accuracy of percentage body fat (%fat) estimates from air displacement plethysmography (ADP) against an increasingly recognised criterion method, dual-energy X-ray absorptiometry (DXA), in young adolescents. DESIGN: Cross-sectional evaluation. SETTING: Leeds General Infirmary, Centre for Bone and Body Composition Research, Leeds, UK. SUBJECTS: In all, 28 adolescents (12 males and 16 females), age (mean+/-s.d.) 14.9+/-0.5 y, body mass index 21.2+/-2.9 kg/m(2) and body fat (DXA) 24.2+/-10.2% were assessed. RESULTS: ADP estimates of %fat were highly correlated with those of DXA in both male and female subjects (r=0.84-0.95, all P<0.001; s.e.e.=3.42-3.89%). Mean %fat estimated by ADP using the Siri (1961) equation (ADP(Siri)) produced a nonsignificant overestimation in males (0.67%), and a nonsignificant underestimation in females (1.26%). Mean %fat estimated by ADP using the Lohman (1986) equations (ADP(Loh)) produced a nonsignificant underestimation in males (0.90%) and a significant underestimation in females (3.29%; P<0.01). Agreement between ADP and DXA methods was examined using the total error (TE) and methods of Bland and Altman (1986). Males produced a smaller TE (ADP(Siri) 3.28%; ADP(Loh) 3.49%) than females (ADP(Siri) 3.81%; ADP(Loh) 4.98%). The 95% limits of agreement were relatively similar for all %fat estimates, ranging from +/-6.57 to +/-7.58%. Residual plot analyses, of the individual differences between ADP and DXA, revealed a significant bias associated with increased %fat (DXA), only in girls (P<0.01). CONCLUSIONS: We conclude that ADP, at present, has unacceptably high limits of agreement compared to a criterion DXA measure. The ease of use, suitability for various populations and cost of ADP warrant further investigation of this method to establish biological variables that may influence the validity of body fat estimates.     

Reproducibility of upper-arm anthropometry in subjects of differing body mass

A study was performed to assess the reproducibility of upper-arm anthropometry using two observers with subjects of differing body mass. Subjects were divided into four groups according to their body mass index:
Group 1: <20
Group 2: >20-<25
Group 3: >25-<30
Group 4: >30-<40.
Results show a much greater observer error related to triceps skinfold thickness than to mid-arm circumference when expressed as restricted coefficient of variation. An increase in observer error in both triceps skinfold thickness and mid-arm circumference with an increase in body mass has also been demonstrated, the error again being greater with triceps skinfold thickness. These results question the validity of work where two or more observers are used to collect data on upper-arm anthropometry without first attempting to quantify observer error and control for body mass.     

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.     

Evaluating body fat in girls and female adolescents: advantages and disadvantages of dual-energy X-ray absorptiometry

BACKGROUND: Within the past 10 y, dual-energy X-ray absorptiometry (DXA) has become one of the most widely used methods of measuring human body composition. However, DXA has not been fully evaluated against an independent criterion method of measuring body fatness in young females. OBJECTIVE: Our objective was to determine the bias and agreement between DXA and a 4-compartment model in predicting the percentage of fat mass (%FM) in a multiethnic group of young females. DESIGN: The %FM values measured by DXA of 73 white, 43 African American, 14 Hispanic, and 11 Asian females with a mean (+/- SD) age of 13.0 +/- 1.9 y were compared with the 4-compartment values, which were based on measurements of body density, body water, and bone mineral content. RESULTS: The %FM values measured by the 2 methods were correlated at r = 0.90 with an SEE of 3.3%; Bland-Altman analysis indicated an average bias of 3.9%. After nullification of the average bias, an individual estimate of %FM by DXA could be underestimated or overestimated by 6.7% when compared with the 4-compartment value. CONCLUSIONS: DXA is an appropriate method for estimating body composition in a group of young females because its bias and limits of agreement are independent of age, ethnicity, and body fatness. However, the limits of agreement of 6.7% could cause an individual FM value to be underestimated or overestimated by 28% relative to the 4-compartment value. Therefore, DXA may not be the optimal method of measuring the body fatness of young females.