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Childhood obesity has become a worldwide health problem. Recent studies have suggested that obese and overweight children have lower bone mass. We used dual-energy X-ray absorptiometry to examine the relation between bone mineral content (BMC) and body fatness (%Fat) in healthy children. Obese children (%Fat>30%) had higher BMC compared with age-, gender-, and ethnic-matched children with normal adiposity (%Fat<25%). When adjusted for height, these differences were less significant. We conclude obese children do not have lower whole-body BMC when compared with leaner children, even when adjusted for height, age, gender, and ethnicity.

Objective: To compare estimates of fat mass (FM), fat-free mass (FFM) and percentage body fat (%fat) by six different methods in prepubertal girls., Design: Cross-sectional study., Subjects: Normal-weight, multi-ethnic, prepubertal girls (age=8.5+/-0.4 y, n=101)., Measurements: Body composition was measured in each child by anthropometry (skinfold thickness using Slaughter equation), dual-energy X-ray absorptiometry (DXA), total body potassium (TBK), isotope dilution for total body water measurement (TBW), multifrequency bioelectrical impedance spectroscopy (BIS), and total body electrical conductivity (TOBEC)., Results: TOBEC and skinfold thickness yielded the lowest values of FM followed by DXA, TBK, TBW and BIS, with BIS giving the highest value of FM. All methods were significantly different for FFM, FM and %fat (P<0.001), except FFM by DXA and TBK. The Bland-Altman limits of agreement among the methods reveal that they are not directly interchangeable for FM, FFM, or %fat. The largest mean difference for FM was between TOBEC and BIS (-2.90 kg), whereas the smallest mean difference was between TOBEC and skinfold thickness (-0.14 kg). For FFM, the largest mean difference was also between TOBEC and BIS (2.83 kg), but the smallest mean difference for FFM was between DXA and TBK (-0.03 kg). For %fat, the mean differences were larger, -10.5% for TOBEC and BIS and+9.7% for skinfold thickness and BIS. The closest two techniques for %fat were TOBEC and skinfold thickness (mean difference of -0.62%) and DXA and TBK (-1.81%)., Conclusions: We found that estimates of body composition in prepubertal 8-y-old girls are highly method-dependent and that the six methods studied (DXA, TBK, TBW, TOBEC, BIS and anthropometry) are not directly interchangeable.

Background: Obesity has been increasing dramatically in recent years among children, particularly African-American girls. Total-body electrical conductivity (TOBEC) is a simple way to measure body fat with minimal risk., Objective: This study compared the agreement between the percentage of fat mass (%FM) predicted using two TOBEC equations with %FM measured by a four-component model in 73 Caucasian and 41 African-American girls., Design and Measurements: %FM predicted using the TOBEC equations was compared with %FM from the four-component model based on measurements of body density, body water and bone mineral content., Results: Analyses by linear regression analysis and by the Bland and Altman methods comparison procedure showed that the equation using the square root of the TOBEC zero-order Fourier coefficient and the subject's height yielded more accurate and more reproducible %FM, regardless of race, than the TOBEC linear equation, which was based on the zero-, first- and second-order Fourier coefficients. The Bland and Altman comparison further revealed that the accuracy and limits of agreement of the TOBEC linear equation were related to body fatness among the Caucasian girls. The relationship, however, disappeared when prepubescent girls and a girl with low %FM were excluded from the analysis., Conclusions: The TOBEC square root equation with adjustment for body geometry and length is recommended for use in adolescent girls, as it yielded better agreement with the criterion method. However, further validation of the TOBEC instrumentation for estimating body fat in prepubescent children and children with low body fat is warranted.

Background: Although skinfold-thickness equations are widely used to estimate body fat, their accuracy in a biracial population of female adolescents has not been established., Objective: We undertook this study to determine the agreement between 8 widely used skinfold-thickness equations and a 4-compartment criterion model in predicting the percentage body fat of 72 white and 40 African American girls aged 13.0 +/- 1.9 y., Design: The biceps, triceps, suprailiac, subscapular, thigh, calf, and abdominal skinfold thicknesses of the subjects were measured with skinfold calipers and the buttocks circumference with a metal tape. The percentage fat mass (%FM) predicted by using each skinfold-thickness equation was compared with the criterion value calculated by the 4-compartment model on the basis of measurements of body density, body water, and bone mineral content., Results: When the racial groups were analyzed separately, the Bland-Altman analysis indicated that the quadratic equations agreed most closely with the 4-compartment model's measurement of %FM. Agreement of the other equations varied with body fatness., Conclusions: The quadratic equation of Slaughter et al is recommended for population studies in female adolescents because of its accuracy and simplicity. However, an individual %FM can be over- or underestimated by approximately 10% when this skinfold-thickness equation is used.

The body mass index (BMI), defined as weight/height, is often used to monitor childhood obesity. BMI values for 979 children (438 White, 283 Black, and 258 Hispanic) aged 3-18 years living in the Houston, Texas, metropolitan area from 1994 to 1998 were compared with percentage of fat (%Fat) measurements obtained by using dual-energy x-ray absorptiometry. The associations between %Fat and BMI were statistically significant (r2 = 0.34-0.70, p < 0.0005) and were gender and ethnic dependent (p < 0.0005), indicating that BMI can provide a general description of the adiposity characteristics of a healthy pediatric population. However, BMI was a poor predictor for the individual child, with a standard error for %Fat of 4.7-7.3% of body weight. It is advantageous to identify accurately, as early as possible, those children who truly have excess adiposity, but this assessment should not be done at the risk of falsely mislabeling a significant number of healthy children as overweight or obese.

Total body levels of nitrogen were measured by prompt-gamma neutron activation analysis in 136 healthy adults in the general population (age 20 to 80 years), in 55 cancer patients, and in 20 obese subjects. In order to evaluate the TBN values for the patients, it was necessary to normalize the data for possible differences due to body habitus. This normalization was defined as the ratio of the measured nitrogen level to a predicted nitrogen level derived from the normal population. The parameters of sex, age, Ht, Wt, and fat were used to calculate expected "normal" values of nitrogen. For the cancer patients, an average TBN deficit of less than 10% was observed. Individual patients, however, showed deviations from the TBNp value as large as 28%. For obese patients, the TBN values were normal to slightly high. When adjusted for body size, the deficit of TBN in the cancer patients was approximately half that observed for TBK.

Objective: The increased prevalence of obesity in the United States has led to the increased use of dualenergy X-ray absorptiometry (DXA) for assessment of body fat mass (TBF) in pediatric populations. We examined DXA precision in order to determine suitable scanning intervals for the measurement of changes in TBF in children. Methods: Short-term precision was based on repeated measurements of 38 children (ages 4-19 y) using a Hologic Delphi A (vers. 12.1). We calculated the root mean square standard deviation (SDRMS), percent coefficient of variation (%CVRMS), then the least significant change (LSC) at the 95% confidence interval for both SDRMS and %CVRMS. Normal growth trends were based on a cross-sectional set of DXA scans of 1410 children (ages 2-20 y). Results: LSCSD for all children was 716 g and 1.4% for TBF and %Fat, respectively, while LSC%CV results were ∼6% for both TBF and %Fat. For TBF, LSCSD was higher for girls than for boys (890 g vs 575 g), while LSC%CV was higher for boys than for girls (7% vs 5%). Conclusions: Short-term precision results suggest that TBF changes of at least 890 g for girls and 575 g for boys are needed in order to detect a true change at the 95% confidence level. An average-sized child should eclipse the LSCSD for TBF during most any year, except at the very young or the oldest ages. A minimal scanning interval of 6 - 8 months may be sufficient when monitoring TBF during the pubertal growth spurt. DXA facilities should consider doing their own precision testing in order to derive accurate LSC thresholds for TBF and %Fat for children. Keywords: DXA, body composition, obesity. [ABSTRACT FROM AUTHOR]