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.     

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.     

Precision and accuracy of dual-energy X-ray absorptiometry for determining in vivo body composition of mice

OBJECTIVE: To evaluate the precision and accuracy of dual-energy X-ray absorptiometry (DXA) for the measurement of total-bone mineral density (TBMD), total-body bone mineral (TBBM), fat mass (FM), and bone-free lean tissue mass (LTM) in mice. RESEARCH METHODS AND PROCEDURES: Twenty-five male C57BL/6J mice (6 to 11 weeks old; 19 to 29 g) were anesthetized and scanned three times (with repositioning between scans) using a peripheral densitometer (Lunar PIXImus). Gravimetric and chemical extraction techniques (Soxhlet) were used as the criterion method for the determination of body composition; ash content was determined by burning at 600 degrees C for 8 hours. RESULTS: The mean intraindividual coefficients of variation (CV) for the repeated DXA analyses were: TBMD, 0.84%; TBBM, 1.60%; FM, 2.20%; and LTM, 0.86%. Accuracy was determined by comparing the DXA-derived data from the first scan with the chemical carcass analysis data. DXA accurately measured bone ash content (p = 0.942), underestimated LTM (0.59 +/- 0.05g, p < 0.001), and overestimated FM (2.19 +/- 0.06g, p < 0.001 ). Thus, DXA estimated 100% of bone ash content, 97% of carcass LTM, and 209% of carcass FM. DXA-derived values were then used to predict chemical values of FM and LTM. Chemically extracted FM was best predicted by DXA FM and DXA LTM [FM = -0.50 + 1.09(DXA FM) - 0.11(DXA LTM), model r2 = 0.86, root mean square error (RMSE) = 0.233 g] and chemically determined LTM by DXA LTM [LTM = -0.14 + 1.04(DXA LTM), r2 = 0.99, RMSE = 0.238 g]. DISCUSSION: These data show that the precision of DXA for measuring TBMD, TBBM, FM, and LTM in mice ranges from a low of 0.84% to a high of 2.20% (CV). DXA accurately measured bone ash content but overestimated carcass FM and underestimated LTM. However, because of the close relationship between DXA-derived data and chemical carcass analysis for FM and LTM, prediction equations can be derived to more accurately predict body composition.     

Body fat and fat-free mass measured by bioelectric impedance spectroscopy and dual-energy X-ray absorptiometry in obese and non-obese adults

The aim of the present study was to compare body fat mass (FM) and fat-free mass (FFM) estimates by bioelectric impedance spectroscopy (BIS), with respective estimates by dual-energy X-ray absorptiometry (DXA), in obese and non-obese subjects. Body composition was measured in ninety-three obese and non-obese men and women by BIS device, BodyScout (Fresenius Kabi, Bad Homburg, Germany) and DXA device, Lunar iDXA (GE Healthcare, Madison, WI, USA). Mean difference between the methods was analysed by t tests, and Bland-Altman plots were generated to further examine the differences between the methods. Mean difference between the estimates by DXA and BIS (ΔDXA - BIS and Bland-Altman 95 % limits of agreement) were as follows: FM 4·1 ( - 2·9, 11·2) kg and 4·5 ( - 2·9, 11·8) %, FFM - 4·1 ( - 11·2, 2·9) kg and - 4·5 ( - 11·9, 2·9) %, indicating large inter-individual variation and statistically significant underestimation of FM and overestimation of FFM by BIS, as compared to DXA. The underestimation of FMkg (FM measured in kg) and overestimation of FFMkg (FFM measured in kg) were more pronounced in men than in women, and the underestimation of FM% (FM measured in percent) and overestimation of FFM% (FFM measured in percent) were more pronounced in normal weight (BMI = 20·0-24·9 kg/m2) than in overweight and obese (BMI ≥ 25·0 kg/m2) subjects. BIS may be suitable for classification of a population into groups according to FM and FFM. However, the large inter-individual variation suggests that this BIS device with the proprietary software is insufficient for estimation of single individual body FM and FFM.     

Body composition assessment: dual-energy X-ray absorptiometry (DEXA) compared to reference methods.

The use of dual energy X-ray absorptiometry (DEXA) for the assessment of body composition was examined in 55 adults (26 male & 29 female) ranging in age from 19 to 65 years. DEXA measures of bone mineral content (BMC, g), bone mineral density (BMD, g/cm2) and soft tissue (ST) were based on differential energy attenuation at dual energy levels of 40 and 70 keV. The ratio of the low- to high-energy attenuation in ST was used to quantify fat (%FatDEXA) and fat-free mass minus the bone component (FFMDEXA). BMC and BMD were significantly correlated (r = 0.82 and 0.60) with densitometric fat-free mass (FFMD). No significant differences were observed between the sum of FFMDEXA + BMC versus FFMD for either the males or females (males: FFMDEXA + BMC = 61.7 kg; FFMD = 59.1 kg; females: FFMDEXA + BMC = 43.8 kg; FFMD = 42.8 kg). Percentage body fat from DEXA for the women was equivalent to percentage fat from density (%FatDEXA = 30.8 versus %FatD = 32.2); however, significant differences were observed for the men (%FatDEXA = 19.4 versus %FatD = 23.5). Percentage fat differences for the men may be due to classification of individual soft tissue pixels. DEXA is reliable, easy to use, and appears to give accurate values for the estimation of FFM for both men and women. Additional research is needed to ascertain the cause of the differences in the estimation of percent body fat for men.     

Conjugated linoleic acid decreases fat accretion in pigs: evaluation by dual-energy X-ray absorptiometry

Thirty female Large White x Landrace pigs (average weight 57.2 (sd 1.9) kg) were allocated to one of six dietary treatments containing 0, 1.25, 2.5, 5.0, 7.5 or 10.0 g 55 % conjugated linoleic acids (CLA) isomers (CLA-55)/kg diet and fed for 8 weeks. Each pig was scanned at 0, 28 and 56 d and again at post slaughter using dual-energy X-ray absorptiometry (DXA) to determine the temporal pattern of body composition responses. Values determined by DXA were adjusted using regression equations generated from validation experiments between chemically and DXA-predicted values. Overall, there was a significant linear reduction in fat content with the increasing levels of CLA in the diet (P=0.007, P=0.011, P=0.008 at week 4, week 8 and for the carcass, respectively). The greatest improvement was recorded at the early stages of CLA supplementation and for the highest dose of CLA (week 4, -19.2 % compared with week 8, -13.7 %). In the first 4 weeks of feeding CLA, pigs receiving 10 g CLA-55/kg diet deposited 93 g less fat/d than pigs fed basal diets (P=0.002) compared with only 6 g less fat than control animals in the final 4 weeks. Lean content and lean deposition rate were maximised at 5 and 2.5 g CLA-55/kg diet for the first 4 weeks (P=0.016) and the final 4 weeks of treatment respectively. DXA estimates of bone mineral content and bone mineral density were not affected by CLA supplementation throughout the experiment. These data demonstrate that dietary CLA decreases body fat in a dose-dependent manner and that the response is greatest over the initial 4 weeks of treatment.     

Body composition measured by dual-energy X-ray absorptiometry in patients who have undergone small-intestinal resection

BACKGROUND: Patients who have undergone resection of the small intestine have lower body weight than do healthy persons. It remains unclear whether it is the body fat mass or the lean tissue mass that is reduced. OBJECTIVE: We compared body-composition values in patients who had undergone small-intestinal resection with reference values obtained in healthy volunteers, and we studied the relation between body-composition estimates and the net intestinal absorption of energy. DESIGN: In a cross-sectional study, we included 20 men and 24 women who had undergone small-intestinal resection and had malabsorption of energy > 2000 kJ/d. Diagnoses were Crohn disease (n = 37) and other conditions (n = 7). Body composition was estimated by dual-energy X-ray absorptiometry, and data were compared with those from a reference group of 173 healthy volunteers. Energy absorption was measured during 48-h balance studies by using bomb calorimetry, and individual values were expressed relative to the basal metabolic rate. RESULTS: Body weight and body mass index in patients were significantly (P < 0.05) lower than the reference values. Fat mass was 6.4 kg (30%) lower (95% CI: -8.8, -3.9 kg), but lean tissue mass was only slightly and insignificantly lower (1.5 kg, or 3.3%; 95% CI: -3.7, 0.60 kg). Weight, body mass index, and body-composition estimates by dual-energy X-ray absorptiometry did not correlate significantly with the net energy absorption relative to the basal metabolic rate, expressed as a percentage. CONCLUSIONS: Patients who had undergone small-intestinal resection had significantly lower body weights and body mass indexes than did healthy persons, and they had significant changes in body composition, mainly decreased body fat mass.     

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.     

Vitamin D status and body fat measured by dual-energy X-ray absorptiometry in a general population of Japanese children

ObjectiveFor a general population of children, data on the relationship between vitamin D status and adiposity are limited. The aim of this study was to assess the relationships between the serum concentration of 25-hydroxyvitamin D (25-OH-D) and body fat variables measured by dual-energy X-ray absorptiometry (DXA) in a general population of Japanese children, including underweight, normal, and overweight children.MethodsThe source population comprised 521 fifth-grade children who attended either of the two public schools in Hamamatsu, Japan. Total and regional body fat mass (FM) measured by DXA were evaluated along with the serum concentration of 25-OH-D.ResultsWe were able to analyze the FM and 25-OH-D data of 400 of the 521 children. Among boys, significant inverse relationships were observed between serum vitamin D levels and body fat variables (total FM, r = ?0.201; trunk FM, r = ?0.216; appendicular FM, r = ?0.187; P < 0.05 for all values). Mean values of total FM and trunk FM in the vitamin D-deficient group (25-OH-D <50 nmol/L) were larger than those in the vitamin D-sufficient group (25-OH-D ≥75 nmol/L) after adjusting for confounding factors, such as sedentary behavior (P < 0.05). No relationship was observed between vitamin D status and FM among girls.ConclusionsVitamin D deficiency was associated with higher total and trunk adiposities in a general population of Japanese children, particularly boys.     

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.     

Measurement of body fat by dual-energy X-ray absorptiometry and bioimpedance analysis in men with prostate cancer

OBJECTIVE: The aims of this study were to determine the percentage of body fat (%BF) by dual-energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) using a standard adult equation and BIA using a standard geriatric equation in a population of older men with prostate cancer and to compare the results from these different methods. METHODS: We conducted a cross-sectional study in 38 men with locally advanced, node-positive, or recurrent prostate cancer and no history of androgen-deprivation therapy. Body composition was evaluated by DXA with the use of a Hologic 4500A densitometer and BIA. BIA %BF was calculated by using standard equations developed for adult and geriatric populations. RESULTS: %BF by DXA, BIA with the standard adult equation, BIA with the standard geriatric equation, and BIA with the age-appropriate equation were 26.7 +/- 5.3%, 22.5 +/- 5.6%, 38.2 +/- 6.9%, and 35.4 +/- 9.6%, respectively. There were statistically significant differences between %BF by DXA and all BIA estimates. By using the methods described by Bland and Altman (Lancet 1986;1(8476):307), the standard adult equation showed the least bias and variability. CONCLUSIONS: In this group of men with prostate cancer, BIA with the standard adult equation provided a reasonable estimate of %BF compared with DXA, although the differences were statistically significant. BIA with the standard geriatric equation, however, markedly overestimated %BF compared with DXA, even when its use was restricted to elderly men.     

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.     

A comparison of skinfold anthropometry and dual-energy X-ray absorptiometry for the evaluation of body fat in cirrhotic patients

BACKGROUND AND AIMS: Skinfold anthropometry has been used to evaluate the nutritional status in cirrhosis. Such estimates are based on the calculations which derive from healthy subjects and may not apply to cirrhotic patients. We aimed to calculate the limits of agreement between Skinfold anthropometry (SA) and dual-energy X-ray absorptiometry (DXA) in estimating body fat in cirrhotics. METHODS: Forty cirrhotic patients were studied by both methods. The limits of agreement were estimated by the Bland and Altman method. RESULTS: Percentage body fat was similar when measured by DXA and SA (29.6 +/- 9.2 vs 28.9 +/- 7.5 %). Body fat mass was also similar (20.3 +/- 8.4 vs 20.3 +/- 7.7 kg). The limits of agreement between DXA and SA measurements were -7.04 (95%CI: -9.55 to -5.2) +8.56 (95%CI: +10.7 to +6.4.) in the assessment of percentage body fat and -5.32 (95%CI: -6.77 to -3.87) +5.24 (95%CI: +3.79 to +6.69) in the assessment of fat mass. CONCLUSION: Percentage body fat can be evaluated by SA or DXA with a difference of less then 5% in the majority of cirrhotic patients without overt fluid retention. This result is important when considering the large applicability of SA.