Body composition and physical activity in New Zealand Maori, Pacific and European children aged 5-14 years

Body fatness and the components of energy expenditure in children aged 5-14 years were investigated. In a group of seventy-nine healthy children (thirty-nine female, forty male), mean age 10.0 (sd 2.8) years, comprising twenty-seven Maori, twenty-six Pacific Island and twenty-six European, total energy expenditure (TEE) was determined over 10 d using the doubly-labelled water method. Resting metabolic rate (RMR) was measured by indirect calorimetry and physical activity level (PAL) was calculated as TEE:RMR. Fat-free mass (FFM), and hence fat mass, was derived from the (18)O-dilution space using appropriate values for FFM hydration in children. Qualitative information on physical activity patterns was obtained by questionnaire. Maori and Pacific children had a higher BMI than European children (P<0.003), but % body fat was similar for the three ethnic groups. The % body fat increased with age for girls (r 0.42, P=0.008), but not for boys. Ethnicity was not a significant predictor of RMR adjusted for FFM and fat mass. TEE and PAL, adjusted for body weight and age, were higher in Maori than European children (P<0.02), with Pacific children having intermediate values. PAL was inversely correlated with % body fat in boys (r -0.43, P=0.006), but was not significantly associated in girls. The % body fat was not correlated with reported time spent inactive or outdoors. Ethnic-related differences in total and activity-related energy expenditure that might account for higher obesity rates in Maori and Pacific children were not seen. Low levels of physical activity were associated with increased body fat in boys but not in girls.     

Assessing body composition among 3- to 8-year-old children: anthropometry, BIA, and DXA

OBJECTIVE: To examine the inter-relationships of body composition variables derived from simple anthropometry [BMI and skinfolds (SFs)], bioelectrical impedance analysis (BIA), and dual energy x-ray (DXA) in young children. RESEARCH METHODS AND PROCEDURES: Seventy-five children (41 girls, 34 boys) 3 to 8 years of age were assessed for body composition by the following methods: BMI, SF thickness, BIA, and DXA. DXA served as the criterion measure. Predicted percentage body fat (%BF), fat-free mass (FFM; kilograms), and fat mass (FM; kilograms) were derived from SF equations [Slaughter (SL)1 and SL2, Deurenberg (D) and Dezenberg] and BIA. Indices of truncal fatness were also determined from anthropometry. RESULTS: Repeated measures ANOVA showed significant differences among the methods for %BF, FFM, and FM. All methods, except the D equation (p = 0.08), significantly underestimated measured %BF (p < 0.05). In general, correlations between the BMI and estimated %BF were moderate (r = 0.61 to 0.75). Estimated %BF from the SL2 also showed a high correlation with DXA %BF (r = 0.82). In contrast, estimated %BF derived from SFs showed a low correlation with estimated %BF derived from BIA (r = 0.38); likewise, the correlation between DXA %BF and BIA %BF was low (r = 0.30). Correlations among indicators of truncal fatness ranged from 0.43 to 0.98. DISCUSSION: The results suggest that BIA has limited utility in estimating body composition, whereas BMI and SFs seem to be more useful in estimating body composition during the adiposity rebound. However, all methods significantly underestimated body fatness as determined by DXA, and, overall, the various methods and prediction equations are not interchangeable.     

中国7~18岁人群应用生物电阻抗法估算体脂方程

目的建立生物电阻抗方法(BIA)测量中国儿童青少年体脂含量的应用方程。方法按《中国学龄儿童青少年超重、肥胖筛查BMI分类标准》中各性别和年龄段超重的BMI参考值,将总人群分为体重正常组和超重肥胖组。以水下称重方法为标准方法,采用多元线性逐步回归方法,建立不同BMI水平7~18岁儿童青少年BIA的应用方程。结果体重正常组方程:去脂体重(FFM,kg)=0.406weight+2.918sex+0.315H2/z+0.843;超重肥胖组方程:FFM(kg)=0.358weight+1.571sex+0.358H2/z+0.603;总人群方程:FFM(kg)=0.290weight+2.222sex+0.427H2/z+1.547。三个方程的调整回归系数(r2)和标准误(SEE)分别为:0.940和2.36;0.955和2.46;0.942和2.53,方程的统计学检验均有显著性意义(ANOVA,P<0.001)。结论本研究建立的BIA应用方程与国内外同类研究相比,具有较高的可靠性。     

Fat-free mass characteristics vary based on sex,race, and weight status in US adults

Common body composition estimation techniques necessitate assumptions of uniform fat-free mass (FFM) characteristics, although variation due to sex, race, and body characteristics may occur. National Health and Nutrition Examination Survey data from 1999 to 2004, during which paired dual-energy x-ray absorptiometry (DXA) and bioimpedance spectroscopy assessments were performed, were used to estimate FFM characteristics in a sample of 4619 US adults. Calculated FFM characteristics included the density and water, bone mineral, and residual content of FFM. A rapid 4-component model was also produced using DXA and bioimpedance spectroscopy data. Study variables were compared across sex, race/ethnicity, body mass index (BMI), and age categories using multiple pairwise comparisons. A general linear model was used to estimate body composition after controlling for other variables. Statistical analyses accounted for 6-year sampling weights and complex sampling design of the National Health and Nutrition Examination Survey and were based on 5 multiply imputed datasets. Differences in FFM characteristics across sex, race, and BMI were observed, with notable dissimilarities between men and women for all outcome variables. In racial/ethnic comparisons, non-Hispanic blacks most commonly presented distinct FFM characteristics relative to other groups, including greater FFM density and proportion of bone mineral. Body composition errors between DXA and the 4-component model were significantly influenced by sex, age, race, and BMI. In conclusion, FFM characteristics, which are often assumed in body composition estimation methods, vary due to sex, race/ethnicity, and weight status. The variation of FFM characteristics in diverse populations should be considered when body composition is evaluated.     

Sex differences in resting energy expenditure and their relation to insulin resistance in children (EarlyBird 13)

BACKGROUND: Insulin resistance is believed to be the process underlying type 2 diabetes and premature cardiovascular disease. We have established that a relation between body mass and insulin resistance calculated by homeostasis model assessment (HOMA-IR) exists by 5 y of age in contemporary UK children. Resting energy expenditure (REE) is variable among individuals and is one of many factors controlling body mass. OBJECTIVE: The objective was to investigate the relations between REE, body mass, and HOMA-IR in young children. DESIGN: EarlyBird is a nonintervention prospective cohort study of 307 healthy 5-y-olds that asks the question: Which children develop insulin resistance and why? REE by indirect calorimetry and HOMA-IR were measured in addition to total body mass, fat-free mass (FFM) by bioimpedance, body mass index (BMI; in kg/m(2)), and skinfold thickness when the mean age of the cohort was 5.9 +/- 0.2 y. RESULTS: Whereas the BMI of the boys was lower than that of the girls (x +/- SD: boys, 15.9 +/- 1.9; girls, 16.5 +/- 1.9; P = 0.03), their REE was higher by 6% (x +/- SD: 4724 +/- 615 compared with 4469 +/- 531 kJ/d; P = 0.002). This difference persisted after adjustment for FFM and other anthropometric variables (P = 0.04). In boys, there was a weak, although significant, inverse correlation between REE and HOMA-IR, independent of fat mass and FFM (boys: r = -0.21, P = 0.03; girls: r = 0.12, P = 0.34). CONCLUSION: There is a sex difference in REE at 6 y of age that cannot be explained by body composition. The difference appears to be intrinsic, and its contribution to sex differences in adiposity and HOMA-IR in children merits further exploration.     

Prediction of fat-free mass and percentage of body fat in neonates using bioelectrical impedance analysis and anthropometric measures: validation against the PEA POD

Accurate assessment of neonatal body composition is essential to studies investigating neonatal nutrition or developmental origins of obesity. Bioelectrical impedance analysis or bioimpedance analysis is inexpensive, non-invasive and portable, and is widely used in adults for the assessment of body composition. There are currently no prediction algorithms using bioimpedance analysis in neonates that have been directly validated against measurements of fat-free mass (FFM). The aim of the study was to evaluate the use of bioimpedance analysis for the estimation of FFM and percentage of body fat over the first 4 months of life in healthy infants born at term, and to compare these with estimations based on anthropometric measurements (weight and length) and with skinfolds. The present study was an observational study in seventy-seven infants. Body fat content of infants was assessed at birth, 6 weeks, 3 and 4·5 months of age by air displacement plethysmography, using the PEA POD body composition system. Bioimpedance analysis was performed at the same time and the data were used to develop and test prediction equations for FFM. The combination of weight+sex+length predicted FFM, with a bias of < 100 g and limits of agreement of 6-13 %. Before 3 months of age, bioimpedance analysis did not improve the prediction of FFM or body fat. At 3 and 4·5 months, the inclusion of impedance in prediction algorithms resulted in small improvements in prediction of FFM, reducing the bias to < 50 g and limits of agreement to < 9 %. Skinfold measurements performed poorly at all ages.     

Familial resemblance of body composition in prepubertal girls and their biological parents

BACKGROUND: Heritability estimates for body mass index (BMI; in kg/m(2)) in children generally have been derived from twin and adoption studies. However, BMI does not reflect total or regional body composition. OBJECTIVE: We evaluated the familial resemblance of body composition between prepubertal girls of normal weight and body fatness and their parents by using state-of-the-art technology. DESIGN: The subjects were 101 girls [mean age: 8.5 +/- 0.4 y; percentage body fat (%BF): 12-30%] and their biological parents. Weight, height, and body composition [fat mass (FM), fat-free mass (FFM), and %BF] were measured with dual-energy X-ray absorptiometry (DXA) and total body potassium (TBK). RESULTS: Weight, height, and BMI showed low-to-moderate similarity between the girls and both their parents (r = 0.29-0.44, P < 0.01). The girls' FM, FFM, and %BF were significantly related to both parents' body composition. Cross-generational equations were developed for DXA, eg, child's %BF = 12.4 + (0.158 paternal %BF) + (0.145 maternal %BF) (adjusted r(2) = 0.16, P < 0.001). Regional analysis with DXA showed that the adjusted r(2) values for the arm, trunk, and leg regions, respectively, were 0.17, 0.33, and 0.31 for lean tissue mass and 0.11, 0.14, and 0.09 for FM. TBK showed a similar relation between parents and girls (r = 0.28-0.47, P < 0.01). Significant heritability (h(2) +/- SE) was detected for BMI (0.35 +/- 0.17, P = 0.03) and %BF measured with DXA (0.50 +/- 0.12, P = 0.0001). CONCLUSION: The body composition of prepubertal girls of normal weight and body fatness is significantly related to the body composition of both biological parents.     

Percent body fat cutoff values for classifying overweight and obesity recommended by the International Obesity Task Force (IOTF) in Korean children

OBJECTIVE: To predict the percent body fat (%BF) cutoff values corresponding to overweight and obesity recommended by the International Obesity Task Force (IOTF) in Korean children and to compare those values with the published cutoff values in Caucasian children. RESEARCH METHODS AND PROCEDURES: The sample consisted of 1083 Korean children and adolescents (555 boys and 528 girls) aged 7-18 years from 3 schools. Body mass index (BMI) and %BF using a bioelectrical impedance analyzer were measured. The classification of overweight and obesity was based on the age- and sex-specific BMI cutoff values of the IOTF guidelines. RESULTS: The predicted %BF cutoff values for overweight and obesity varied by age and sex: overweight, 17-22% in boys and 24-37% in girls; obesity, 24-30% in boys and 30-53% in girls. Those %BF cutoff values in older Korean boys tended to be lower than the published %BF cutoff values in Caucasian boys. While %BF cutoff values for overweight in Korean girls were similar to the values in Caucasian girls, %BF cutoff values for obesity in Korean girls aged 13-18 years were higher compared to cutoff values in Caucasian girls. CONCLUSION: The %BF values associated with the IOTF-recommended BMI cutoff values for overweight and obesity may require age- and sex-specific cutoff values in Korean children aged 7-18 years.     

Body composition interpretation. Contributions of the fat-free mass index and the body fat mass index

OBJECTIVE: Low and high body mass index (BMI) values have been shown to increase health risks and mortality and result in variations in fat-free mass (FFM) and body fat mass (BF). Currently, there are no published ranges for a fat-free mass index (FFMI; kg/m(2)), a body fat mass index (BFMI; kg/m(2)), and percentage of body fat (%BF). The purpose of this population study was to determine predicted FFMI and BFMI values in subjects with low, normal, overweight, and obese BMI. METHODS: FFM and BF were determined in 2986 healthy white men and 2649 white women, age 15 to 98 y, by a previously validated 50-kHz bioelectrical impedance analysis equation. FFMI, BFMI, and %BF were calculated. RESULTS: FFMI values were 16.7 to 19.8 kg/m(2) for men and 14.6 to 16.8 kg/m(2) for women within the normal BMI ranges. BFMI values were 1.8 to 5.2 kg/m(2) for men and 3.9 to 8.2 kg/m(2) for women within the normal BMI ranges. BFMI values were 8.3 and 11.8 kg/m(2) in men and women, respectively, for obese BMI (>30 kg/m(2)). Normal ranges for %BF were 13.4 to 21.7 and 24.6 to 33.2 for men and women, respectively. CONCLUSION: BMI alone cannot provide information about the respective contribution of FFM or fat mass to body weight. This study presents FFMI and BFMI values that correspond to low, normal, overweight, and obese BMIs. FFMI and BFMI provide information about body compartments, regardless of height.     

Assessment of body composition by bioelectrical impedance in children and young adults is strongly age-dependent

Body composition was measured in a group of 246 children and young adults, ranging in age from 7 to 25 years, by means of densitometry, body impedance (R) and anthropometry. Body fat percentage and fat-free mass (FFM) were calculated from body density using age-specific calculation formulas. From body impedance, FFM and body height, the specific impedance of the body (rho = R*FFM/height) was calculated in which body impedance is corrected for differences in the shape of the conductor. From age 10 onwards the specific impedance was positively related with age until age 13 in girls and age 16 in boys, after which it stabilized in boys at a significantly higher level than in girls. Based on the relationship of the specific impedance with age and sex, three age groups could be defined in which the relation between FFM and body impedance was analysed: age group I, boys and girls younger than 10 years; age group II, boys aged 10-15 years, girls aged 10-12 years; age group III, boys 16 years and older, girls 13 years and older. The regression equation in age group I had the same slope as the sex-specific regression equations in age group III. The regression equation in age group II had a steeper slope compared to the regression equations in age group I and III. Thus the relationship between FFM and body impedance was found to be slightly S-shaped, being identical for boys and girls until age 13, after which sex differences became apparent. For the different age categories the best prediction formula for the FFM from body impedance, sex, age and anthropometric variables was calculated. The prediction error of the age-specific regression equations was lower than the prediction error of the regression equation for the entire population.     

Risk factors for excess body fatness in New Zealand children

OBJECTIVE: To identify demographic and lifestyle risk factors for excess body fatness in a multiethnic sample of New Zealand children. DESIGN: Cross-sectional study. PARTICIPANTS: A total of 1229 European, Polynesian, Asian, and 'Other' children aged 5-11 y (603 male, 626 female) living in New Zealand. MEASUREMENTS: Percentage body fat (%BF) was measured using hand-to-foot bioelectrical impedance analysis, and overfat participants were defined as those with a %BF greater than 25% (boys) and 30% (girls). A parent proxy questionnaire was developed for assessing demographic and lifestyle factors, and multiday memory pedometers were used to estimate physical activity levels over five days. RESULTS: After controlling for differences in sex, age, and socioeconomic status (SES), Asian children were more likely to have excess body fat than European children. The adjusted odds of overfat also increased with age and decreased with SES. Three lifestyle risk factors related to fat status were identified: low physical activity, skipping breakfast, and insufficient sleep on weekdays. Clustering of these risk factors resulted in a cumulative increase in the prevalence of overfat. Active transport, sports participation, lunch bought at school, fast food consumption, sugary drink consumption, and weekend sleep duration were not associated with fat status after adjustment for the selected demographic variables. CONCLUSION: The findings from this study enhance our understanding of the risk factors for excess body fatness in New Zealand children, and highlight key demographic and lifestyle priorities for future interventions.     

Body fat distribution, body composition, and respiratory function in elderly men

BACKGROUND: Most population studies have reported weak or nonsignificant associations between body mass index (BMI; in kg/m2) and lung function. OBJECTIVE: This study focused on the distinct effects of fat distribution and body composition on lung function and examined these relations in elderly men. DESIGN: The study was a cross-sectional evaluation of 2744 men aged 60-79 y who were free of cardiovascular disease and cancer and were drawn from general practices in 24 British towns. Anthropometric and body-composition [including fat mass (FM), fat-free mass (FFM), and percentage body fat (%BF) evaluated with bioelectric impedance] measurements were made, and lung function was examined by using spirometry. RESULTS: Height-standardized forced expiratory volume in 1 s (FEV1) was diminished only in lean (BMI < 22.5) and obese (BMI > or = 30) men, but forced vital capacity (FVC) tended to decrease with increasing BMI (P < 0.01). All other measures of adiposity [ie, waist circumference (WC), waist-hip ratio (WHR), FM, and %BF] were significantly and inversely related to FEV1 and FVC after adjustment for confounders, including age and cigarette smoking (all: P < 0.05). This was seen both in nonobese (BMI < 30) and obese men. FFM was positively associated with FEV1 (P = 0.03) and to a lesser extent with FVC. Higher BMI and FFM were both associated with reduced odds of a low FEV1-FVC ratio (ie, <70%). CONCLUSION: Total body fat and central adiposity are inversely associated with lung function, but increased FFM reflecting increases in muscle mass is associated with increased lung function and lower odds of low FEV1:FVC in the elderly.     

Field methods for body composition assessment are valid in healthy chinese adults

There is little information on the accuracy of simple body composition methods in non-Western populations. We determined the percentage of body fat (%BF) by isotope dilution [oxygen-18 (H(2)(18)O) and deuterium oxide ((2)H(2)O)] and anthropometry in 71 healthy, urban Chinese adults aged 35-49 y [body mass index (BMI) 18-35 kg/m(2)]. The accuracy of several prediction equations for assessment of %BF from skinfold measurements was evaluated against %BF determined by H(2)(18)O dilution. We also assessed the relationship between BMI and %BF, and the fat-free mass (FFM) hydration coefficient for our population. All skinfold equations yielded means within approximately 2%BF of H(2)(18)O-derived %BF. However, on the basis of residual plot analysis and the 95% confidence interval (CI) for the mean difference between methods, the equations of Durnin and Womersley (for assessment of body density from skinfolds) coupled with that of Brozek et al. (for assessment of %BF from body density) provided the most valid assessment for individuals. In addition, the FFM hydration coefficient averaged 0.734 +/- 0.002 (SEM), indicating that the usually assumed value of 0.732 is appropriate for this population. Finally, although BMI had high specificity (90%) for classifying individuals as having body fat within the normal range (<24%BF for men, and <35%BF for women), it had poor sensitivity (66%) for identifying individuals as having high body fat. We conclude that compared with H(2)(18)O dilution, skinfold thickness can provide an accurate and reliable assessment of body composition in healthy Chinese adults. Furthermore, using the equation of Brozek et al. may be preferable to using Siri's equation to predict %BF from body density in populations in which individuals have >30%BF.     

Ethnic differences in the relationship between body mass index and percentage body fat among Asian children from different backgrounds

Overweight and obesity in Asian children are increasing at an alarming rate; therefore a better understanding of the relationship between BMI and percentage body fat (%BF) in this population is important. A total of 1039 children aged 8-10 years, encompassing a wide BMI range, were recruited from China, Lebanon, Malaysia, The Philippines and Thailand. Body composition was determined using the 2H dilution technique to quantify total body water and subsequently fat mass, fat-free mass and %BF. Ethnic differences in the BMI-%BF relationship were found; for example, %BF in Filipino boys was approximately 2 % lower than in their Thai and Malay counterparts. In contrast, Thai girls had approximately 2.0 % higher %BF values than in their Chinese, Lebanese, Filipino and Malay counterparts at a given BMI. However, the ethnic difference in the BMI-%BF relationship varied by BMI. Compared with Caucasian children of the same age, Asian children had 3-6 units lower BMI at a given %BF. Approximately one-third of the obese Asian children (%BF above 25 % for boys and above 30 % for girls) in the study were not identified using the WHO classification and more than half using the International Obesity Task Force classification. Use of the Chinese classification increased the sensitivity. Results confirmed the necessity to consider ethnic differences in body composition when developing BMI cut-points and other obesity criteria in Asian children.     

Body fat percentages measured by dual-energy X-ray absorptiometry corresponding to recently recommended body mass index cutoffs for overweight and obesity in children and adolescents aged 3-18 y

BACKGROUND: Body mass index (BMI; in kg/m2) cutoffs for use with children and adolescents aged 2-18 y that correspond to the well-accepted BMI cutoffs for overweight (> or = 25 but < 30) and obesity (> or = 30) in adults were published recently. OBJECTIVE: The objective was to estimate the percentage body fat (%BF) values typically associated with these BMI cutoffs in children and adolescents. DESIGN: The %BF was measured by dual-energy X-ray absorptiometry in 661 subjects (49% male) aged 3-18 y. Regression equations using BMI, age, and sex were developed to predict the %BF associated with BMI cutoffs for overweight (age-specific BMI equivalent to a BMI of 25 in an 18-y-old) and obesity (age-specific BMI equivalent to a BMI of 30 in an 18-y-old) over this age range. RESULTS: Measurements classified 17.1% of males and 19.8% of females as overweight and 5.5% of males and 7.5% of females as obese. The %BF associated with an obese BMI tended to be higher in peripubertal males (34-36%) than in younger (24-30%) or older (27-30%) males. Although the predicted %BF of young females was similar to that of young males, values rose steadily with age, such that an 18-y-old female with a BMI of 30 had an estimated %BF of 42%, whereas that in males of similar age was 27%. CONCLUSION: The %BF values associated with BMI classifications of overweight and obesity vary considerably with age in growing children, particularly in girls.     

Short-term repeatability of a food frequency questionnaire in New Zealand children aged 1-14 y

OBJECTIVE: To evaluate the repeatability of a children's food frequency questionnaire (FFQ) by gender, ethnicity, and age group. DESIGN: A 117-item FFQ asking about food intake patterns over the past 4 weeks was developed using food records from 428 children (204 boys and 224 girls) and the reproducibility on average 13 days apart was tested in 130 children (78 boys and 52 girls). Children were recruited using clustered probability sampling (n=103), and a convenience sample of 25 Maori children. SETTING: Children aged 1-14 y from Auckland, Feilding and Shannon, New Zealand. SUBJECTS: There were 71 Maori, 20 Pacific, and 39 Other children. RESULTS: Spearman correlations between the two FFQs ranged from 0.50 for bread to 0.82 for fruit, with a median of 0.76 for spreads and nonmilk drinks, and Cronbach's coefficient alpha's ranged from 0.59 for bread to 0.92 for nonmilk drinks, with a median of 0.85 for mixed meat dishes. There were no significant differences between the two administrations, apart from reporting higher intakes of vegetables and snacks & sweets in the first FFQ. Correlation coefficients tended to be slightly higher in boys than in girls, and in Other ethnic groups compared to Maori and Pacific children. Correlations were slightly higher for the 1-4 y age group, intermediate in the 10-14 y age group, and lowest in the 5-9 y-old age group. CONCLUSIONS: Overall, the FFQ described here shows similar or better repeatability in New Zealand children of all major ethnic groups compared to other child or adolescent FFQs.     

Comparison of fat-free mass and body fat in Swiss and American adults

OBJECTIVE: No current studies have compared North American with European body composition parameters, i.e., fat-free mass (FFM), body fat (BF), and percentage of BF (%BF) in large populations. This study compared FFM, BF, and %BF values derived from two bioelectrical impedance analysis (BIA) equations (Geneva and National Health and Nutrition Examination Survey [NHANES]) in Swiss subjects and compared FFM, BF, and %BF values of white Swiss with those of white North American adults with the same BIA equations. METHODS: Healthy adults (3714 men and 3199 women), ages 20 to 79 y, in Switzerland were measured by single-frequency BIA and compared with means and standard deviations for body mass index and body composition parameters obtained from the NHANES III study (United States; n = 2538 men, 2862 women). FFM was calculated with the Geneva and NHANES equations. RESULTS: Mean FFMGENEVA values did not differ from FFMNHANES values in men but was significantly lower (-1.5 kg) in women. FFM and BF values in American men, who weighed 4.2 to 12.0 kg more than the Swiss men, were significantly higher (+2.1 to +6.0 kg and +1.5 to +6.4 kg, respectively) than those in the Swiss men. FFM and BF values in American women, who weighed 2.3 to 12.1 kg more than the Swiss women, were significantly higher (+1.3 to +2.1 kg and +4.8 to +11.8 kg, respectively, except FFM in subjects ages 20 to 29 y and BF in those ages 70 to 79 y) than FFMGENEVA values in Swiss women. FFM in American women was significantly lower (+1.3 and +1.9 kg) and non-significantly higher than FFMNHANES in Swiss women. CONCLUSION: NHANES and Geneva BIA equations estimate body composition equally well in men, but further research is necessary to determine the discrepancies in FFM between BIA equations in women. The greater weight of the American subjects yielded higher values for FFM, BF, and %BF in American than in Swiss men and women.     

Dual-energy X-ray absorptiometry for body composition estimation in Chinese women

OBJECTIVE: To determine whether dual-energy X-ray absorptiometry (DXA) is a valid method for body composition assessment of obese and non-obese subjects. DESIGN: Cross-sectional study. SUBJECTS: Chinese women living in Hong Kong; 66 of 91 subjects had body mass index (BMI) of >25 kg/m2. MEASUREMENTS: Anthropometrics, including body weight, body height, waist and hip girth. Percentage body fat (%BF) and fat-free mass (FFM) from DXA (Hologic 2000 plus, Enhanced Array Whole Body Version 5.63) were compared with that based on a tracer dose of deuterium oxide for the determination of total body water (TBW). RESULTS: In both obese and non-obese subjects, FFMDXA was similar to FFMTBW. The Bland and Altman-type analysis indicated that comparable between-methods differences (mean bias) and limits of agreement were obtained in obese and non-obese subjects for FFM (0.4, between -4.4 and 5.2 kg vs 0.5, between -3.1 and 4.1 kg) and %BF (-0.6, between -7.6 and 6.4% vs -1.2, between -8.6 and 6.2%). The %BF bias was independent of age, BMI, hip circumference, and waist-to-hip ratio, but correlated with waist girth (r=0.24, P=0. 021). CONCLUSION: The sources of bias are methodological and anthropometric in nature. The between-methods differences, however, are small and clinically insignificant. DXA is a valid method for assessing the body composition of obese patients. SPONSORSHIP: This study was supported by a HKU-CRCG grant.     

Influence of methods used in body composition analysis on the prediction of resting energy expenditure

OBJECTIVE: There are considerable differences in published prediction algorithms for resting energy expenditure (REE) based on fat-free mass (FFM). The aim of the study was to investigate the influence of the methodology of body composition analysis on the prediction of REE from FFM. DESIGN: In a cross-sectional design measurements of REE and body composition were performed. SUBJECTS: The study population consisted of 50 men (age 37.1+/-15.1 years, body mass index (BMI) 25.9+/-4.1 kg/m2) and 54 women (age 35.3+/-15.4 years, BMI 25.5+/-4.4 kg/m2). INTERVENTIONS: REE was measured by indirect calorimetry and predicted by either FFM or body weight. Measurement of FFM was performed by methods based on a 2-compartment (2C)-model: skinfold (SF)-measurement, bioelectrical impedance analysis (BIA), Dual X-ray absorptiometry (DXA), air displacement plethysmography (ADP) and deuterium oxide dilution (D2O). A 4-compartment (4C)-model was used as a reference. RESULTS: When compared with the 4C-model, REE prediction from FFM obtained from the 2C methods were not significantly different. Intercepts of the regression equations of REE prediction by FFM differed from 1231 (FFM(ADP)) to 1645 kJ/24 h (FFM(SF)) and the slopes ranged between 100.3 kJ (FFM(SF)) and 108.1 kJ/FFM (kg) (FFM(ADP)). In a normal range of FFM, REE predicted from FFM by different methods showed only small differences. The variance in REE explained by FFM varied from 69% (FFM(BIA)) to 75% (FFM(DXA)) and was only 46% for body weight. CONCLUSION: Differences in slopes and intercepts of the regression lines between REE and FFM depended on the methods used for body composition analysis. However, the differences in prediction of REE are small and do not explain the large differences in the results obtained from published FFM-based REE prediction equations and therefore imply a population- and/or investigator specificity of algorithms for REE prediction.     

A longitudinal comparison of body composition by total body water and bioelectrical impedance in adolescent girls

Previous studies have assessed the ability of bioelectrical impedance analysis (BIA) to estimate body composition cross-sectionally, but less is known about the ability of BIA to detect changes in body composition longitudinally over the adolescent growth period. Body composition was assessed by isotopic dilution of H(2)(18)O and BIA in 196 initially nonobese girls enrolled in a longitudinal study. Two prediction equations for use in our population of girls were developed, one for use premenarcheally and one for use postmenarcheally. We compared estimates from our equation with those derived from several published equations. Using longitudinal data analysis techniques, we estimated changes in fat-free mass (FFM) and percentage body fat (%BF) over time from BIA, compared with changes in FFM and % BF estimated by H(2)(18)O. A total of 422 measurements from 196 girls were available for analysis. Of the participants, 26% had one measurement of body composition, 43% had two measurements of body composition and 31% had three or more measurements of body composition. By either H(2)(18)O or BIA, the mean %BF at study entry was 23% (n = 196) and the mean %BF at 4 y postmenarche was 27% (n = 133). In our cohort, the best predictive equations to estimate FFM by BIA were: PREMENARCHE: FFM = -5.508 + (0.420 x height(2)/resistance) + (0.209 x weight) + (0.08593 x height) + (0.515 x black race) - (0.02273 x other race). POSTMENARCHE: FFM = -11.937 + (0.389 x height(2)/resistance) + (0.285 x weight) + (0.124 x height) + (0.543 x black race) + (0.393 x other race). Overall, we found that BIA provided accurate estimates of the change in both FFM and %BF over time.