Ultrasonic measurements of subcutaneous adipose tissue thickness in man

Subcutaneous adipose tissue thickness (SCATT) has for many years been measured using skinfold calipers, but calipers have several disadvantages, not least that they compress the skinfold. Measuring SCATT using ultrasound was validated by comparing thicknesses at 12 sites with soft-tissue radiographs in 24 adults and with depth gauge measurements on a cadaver. Correlation coefficients ranged from 0.87 to 0.99, and the regression statistics showed no significant difference between ultrasound and the other procedures. The standard errors of estimate of body density from SCATT measured by calipers and ultrasound in 63 young men was +/- 7.8 and 7.3 kg X m-3, respectively. Although problems in the identification of the adipose tissue-muscle interface can arise, ultrasound is a viable alternative to skinfold calipers and is to be preferred when measuring uncompressed SCATT.     

Measurement of subcutaneous adipose tissue using ultrasound images.

The objectives of this paper are to explore the potential of the ultrasound technique to quantify subcutaneous adipose tissue, and to explain the differences between skinfolds and ultrasound measurements across a large range of ages and levels of adiposity. The sample consisted of 115 men and 117 women aged 35 to 51 years, 132 girls and 145 boys aged 12 to 20 years. Subcutaneous fat thickness was measured at four sites using skinfolds calipers, and at seven sites using a real-time B-mode ultrasound scanner. Anthropometric measurements were obtained, and percent body fat was estimated using electric impedance. The agreement between skinfolds and ultrasound measurements was calculated for each age and sex group. The agreement between techniques, and the levels of correlation between body composition and fatness measurements were high in the sample of young men. However, the results were less consistent in the other groups. Site specific differences were also noted.     

Trends and developments in physical anthropology, 1978-1979

Members of the American Association of Physical Anthropologists were asked to supply information about their current programs and their own graduate training in order to compile a training directory and to analyze certain aspects of the discipline. The data indicate that the majority consider their graduate training to have been deficient, mainly in statistics, genetics, chemistry, physiology, and mathematics. The areas though most important for future research in physical anthropology include fields such a genetics, anatomy, ecology, physiology, and paleontology, although a great many individuals are engaged in teaching and research in other areas. A brief analysis of relative growth in the field over the last few decades indicates a serious imbalance between the number of new Ph.D.'s and available employment opportunities.     

Racial differences in subcutaneous fat patterns in children aged 7–15 years

In a stratified random sample of 278 children aged 7–15 years of an entire biracial community, skinfold measurements were taken on six standard body sites. We found that white children had generally thicker skinfolds than blacks for the same body weight, with a consistent exception: the subscapular skinfold was relatively thicker in blacks. It is suggested that this racial difference in distribution of fat may manifest a genetic adaptive trait developed under circumstances demanding both a caloric reserve and facilitation of convective heat loss in tropical climates.     

Interobserver reliability of skinfold measurements in infants and young children

Interobserver reliabilities were determined for the triceps, biceps, subscapular, suprailiac, and abdominal skinfolds in 77 children, 9-24 months of age. Technical errors of measurement (replicate variances) and coefficients of variation were compared to data on 12-17-year-olds from the U.S. Health Examination Survey (HES) to 2.5-7-year-old Guatamalan children. Of the five skinfolds, the between-observer variation was not significantly different from zero in four; in the case of the biceps fold, F-ratio was significant at p less than .01. Errors of measurement are less for these data than for the HES or Guatemalan studies. This difference is attributed to the larger means of the older children and youth, as well as to the greater error of measurement shown to exist for larger skinfolds.     

A multivariate analysis of fatness and relative fat patterning.

Skinfold measurements (triceps, subscapular, suprailiac and medial calf) in four samples (376 boys, 352 girs, 338 men and 380 women from rural Colombia) were subjected to principal components analysis to identify components of obesity and relative fat patterning. Three components emerged which were similar in the four samples: a first component of fatness explaining 70-80% of the variance and two fat pattern components each explaining 10-15% of the variance: trunk-extremity and upper-lower body. Fatness and the trunk-extremity pattern components changed with age in children (7-12 years), but none of the components changed with age in adults (25-60+). The fatter tended to be more patterned in both age groups. Canonical correlation analysis revealed that socioeconomic status was more related to fatness than to patterning. With the exception of brothers, all first degree relatives (sib, parent-off-spring) and spouses were correlated in fatness. Some of the correlations between relatives--usually sibs, but not spouses--were also significant for the pattern components, suggesting a genetic basis for the known stability of this characteristic (Garn, '55a). Principal components analysis is a useful multivariate alternative for quantitative studies of anthropometric patterning.     

Bias and limits of agreement between hydrodensitometry, bioelectrical impedance and skinfold calipers measures of percentage body fat

Previous research has often used correlations as a statistical method to show agreement; however, this is not a valid use of the statistic. The purpose of this study was to investigate the bias and limits of agreement for three methods of estimating percentage body fat for 117 male and 114 female university athletes: hydrodensitometry (HYD), bioelectrical impedance (BIA) and skinfold calipers (SKF). The mean (SD) percentage body fat for males as assessed by HYD, BIA and SKF methods, respectively, were 13.2 (3.3)%, 14.1 (3.3)% and 13.0 (3.2)%. Female body fat measurements were 22.5 (3.9)%, 23.7 (4.3)% and 23.8 (4.2)%, respectively. Pearson product moment correlations for male and female body fat percentages between the three methods were high, ranging from 0.81 to 0.86 (P < 0.05). However, compared to the criterion measure of body fat percentage (HYD), the magnitude of agreement BIA and SKF revealed a different pattern. The mean absolute difference between HYD and BIA measurements of body fat for males was −0.8 (2.0)% fat, and between HYD and SKF was it was 0.2 (1.7)% fat. The mean absolute difference for females between HYD and BIA was −1.2 (2.5)%; for HYD and SKF it was −1.4 (2.2)%. Compared to the HYD measures for males and females, the BIA and SKF measures were as much as a 3.8% underestimation and a 6.2% overestimation of body fat. This study provides evidence that the strength of a correlation does not indicate agreement between two methods. In future, reliability and validity studies should examine the absolute differences between two variables and calculate limits of agreement around which a practitioner can appreciate the precision of the methodologies. Accepted: 26 August 1997     

Comparison of body composition in middle-aged and elderly males using computed tomography

Computed tomography (CT) scans were taken of 21 middle-aged men (mean age 46.3 years) and 20 older men (mean age 69.4 years) to measure differences in body composition with age. Overall, the older men weighed 8.2 kg less than the middle-aged men, and this difference was primarily the result of their having less lean tissue. Although fat mass (by whole body potassium counting) was only slightly less in older men, there were distributional differences in fat between the age groups. Total abdomen adipose tissue area (from CT) was similar in both groups, although the subcutaneous portion of the abdomen adipose tissue was less in the older men, and they had correspondingly more adipose tissue within the abdominal cavity. Muscle areas of the leg and arm were significantly less in the older men, as were all lean tissues of the abdomen and chest. When these data were corrected for differences in body weight with age, the results were still significant, suggesting a centripetalization and internalization of fat with age. Causes of this apparent fat redistribution and decrease of lean tissue with age were not revealed by this study and are presently unknown.     

Body composition assessment of young tennis players by multi-frequency impedance measurements

Body composition was estimated in 169 young tennis players using the multi-frequency impedance method to predict their fatfree-mass, fat, extra-cellular water, and total body water. Bioelectrical impedances at 1, 5, 10, 50 and 100 kHz were determined. Ratios of impedance at low to high frequencies (Z1/Z100; Z5/Z100) were also used as indicators of body water distribution. This sample is characterized by a greater body mass — fat mass, above all-than other Italian sport participants. Sexual dimorphism in body composition is also evident in this sample. The parameters of body composition, predicted by impedance measurements were compared with parameters obtained through other methods (skinfolds and BMI) on the same subjects. Results varied considerably, in relation to the various equations or different techniques employed. Besides demonstrating the value of multifrequency impedance measurements in the assessment of body composition, our findings indicate the necessity of further methodological research to validate the method under controlled conditions.     

Estimation of body composition from bioelectrical impedance of body segments

This study provides values of anthropometric measurements and specific impedance, for a sample of 104 adults. The hypothesis that the body composition can be estimated more accurately from measurements of lengths and impedance values of the body segments than from the whole body was tested. The impedance of upper and lower extremities (arm and leg) and trunk were used to compute estimates of body composition parameters (FFM, FM, %F, TBW, ECW). The results were compared with those estimated by the impedance of the whole body. These comparisons demonstrated that significative differences resulted from body composition obtained by segmental impedance and by the whole body.     

Predictive regression modeling of body segment parameters using individual-based anthropometric measurements

Body segment parameters such as segment mass, center of mass, and radius of gyration are used as inputs in static and dynamic ergonomic and biomechanical models used to predict joint and muscle forces, and to assess risks of musculoskeletal injury. Previous work has predicted body segment parameters (BSPs) in the general population using age and obesity levels as statistical predictors (Merrill et al., 2017). Estimated errors in the prediction of BSPs can be as large as 40%, depending on age, and the prediction method employed (Durkin and Dowling, 2003). Thus, more accurate and representative segment parameter inputs are required for attempting to predict modeling outputs such as joint contact forces, muscle forces, and injury risk in individuals. This study aims to provide statistical models for predicting torso, thigh, shank, upper arm, and forearm segment parameters in working adults using whole body dual energy x-ray absorptiometry (DXA) scan data along with a set of anthropometric measurements. The statistical models were developed on a training data set, and independently validated on a separate test data set. The predicted BSPs in validation data were, on average, within 5% of the actual in vivo DXA-based BSPs, while previously developed predictions (de Leva, 1996) had average errors of up to 60%, indicating that the new models greatly increase the accuracy in predicting segment parameters. These final developed models can be used for calculating representative BSPs in individuals for use in modeling applications dependent on these parameters.     

The Diabetes Alert study: growth, fatness, and fat patterning, adolescence through adulthood in Mexican Americans

Diabetes Alert is a multidisciplinary genetic and epidemiological study of Type II (non insulin-dependent) diabetes in Texas Mexican Americans. We report the anthropometry of 1,155 individuals 10 to 70 or more years with particular reference to overweight, fatness, and anatomical fat patterning in the sample. Children ages 10-18 of both sexes are growing at the 50th percentile of the reference data (U.S. Health and Nutrition Examination Survey-1) for height, Wt/Ht2, and triceps and subscapular skinfolds. Adults are well below median height but well above median Wt/Ht2 and skinfolds. Prevalence of obesity (Wt/Ht2 greater than or equal to 30) among adults is typically 30% or higher by age 30. Diabetics compared to age/sex-matched non diabetics have shorter sitting heights, have more upper body fat (subscapular skinfold), have less lower body fat (lateral calf skinfold), and were heavier at maximum weight and at age 18. The ratio of lower to upper body fat distribution decreases over the life cycle, being highest at adolescence and lowest at ages 40-50 in both sexes. Our results show a precipitous weight gain after maturity in the sample and an association of diabetes with differences in anatomical fat patterning. The age-related changes in fat patterning need to be explained in terms of their ecological and genetic influences.     

Food prices and body fatness among youths

We examine the effect of food prices on clinical measures of obesity, including body mass index (BMI) and percentage body fat (PBF) measures derived from bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA), among youths ages 12 through 18 in the National Health and Nutrition Examination Survey. This is the first study to consider clinically measured levels of body composition rather than BMI to investigate the effects of food prices on obesity outcomes among youths classified by gender and race/ethnicity. Our findings suggest that increases in the real price per calorie of food for home consumption and the real price of fast-food restaurant food lead to improvements in obesity outcomes among youths. We also find that a rise in the real price of fruits and vegetables leads to increased obesity. Finally, our results indicate that measures of PBF derived from BIA and DXA are no less sensitive and in some cases more sensitive to the prices just mentioned than BMI, and serve an important role in demonstrating that rising food prices (except fruit and vegetable prices) are indeed associated with reductions in obesity rather than with reductions in body size proportions alone.     

Relative reliability of circumferences and skinfolds as measures of body fat distribution

The question has arisen whether patterns of body fat distribution can be identified by body circumferences, a method which is said to be more reliable and simpler than skinfold thickness or like measures of subcutaneous fat (Ashwell et al., Int. J. Obes. 6: 143-152, 1982). Here we address the question of whether body circumferences are inherently more reliable than skinfold thicknesses in 77 intra- and 224 interexaminer replicates from the Health Examination Survey of 12 to 17-year-olds in the U.S.A. Reliability of six body circumferences (0.96) was significantly (P less than .01) higher than that of skinfold thicknesses at five sites (0.91), suggesting that circumferences are a more reliable method. However, the reliability of skinfolds is still high, and skinfolds may be used in studies which focus on preadults or other groups in which the validity of circumferences as measures of body fat distribution is unknown.     

Relationship of the body mass index with skinfolds,girths, and bone breadths in canadian men and women aged 20–70 years

The relationships of Quetelet index (w/h²), or body mass index (BMI), with the sum of skinfolds at five sites, two skinfold-corrected limb girths, and two bone breadths were studied in a cross-sectional sample of 12,282 men and 6,593 women aged 20–70 years. The correlations of the BMI with skinfolds (0.50), bone breadths (0.51), and girths (0.58) were too low for individual prediction. Contingency tables of the BMI and sum of skinfold categories further indict its use for the purpose of assessing adiposity status or monitoring change in individuals.     

Estimation of total water and fatness from weight and height: inaccurate for lean women

Mellits and Cheek have provided a regression equation which predicts total water, and by extension, fat, from weight and height of women. The equation has been used by many researchers as a convenient means to estimate fat when more complicated body composition estimation techniques are not possible. It is an essential component of evidence provide by Frisch for the critical fat hypothesis. The equation has not been validated on another sample, however, and has a large standard error. I test the Mellits and Cheek equation on five samples of young women, two of which show a normal range of heights and weights. The other three are athletic samples composed of lean women. In the normal samples mean fat percent determined by density (from underwater weighing) is closely approximated by the weight and height equation but not in the lean samples. When measured fat is regressed on estimated fat, correlations are low, and standard errors are high, suggesting that the Mellits and Cheek equation predicts poorly the body fat percentage of individual females. In summary, the Mellits and Cheek equation is moderately useful for the prediction of group means for body composition on samples with normal ranges of height and weight. It does not produce acceptable results on groups selected for extreme leanness or obesity. It is not recommended for fat prediction of individuals.     

Bioelectrical impedance underestimates total and truncal fatness in abdominally obese women

Objective: To compare estimates of total and truncal fatness from eight‐electrode bioelectrical impedance analysis equipment (BIA₈) with those from DXA in centrally obese women. The secondary aim was to examine BMI and waist circumference (WC) as proxy measures for percentage total body fat (%TBF) and truncal body fat percentage (tr%BF). Research Methods and Procedures: This was a cross‐sectional study of 136 women (age, 48.1 ± 7.7 years; BMI, 30.4 ± 2.9 kg/m²; %TBF_DXA, 46.0 ± 3.7%; WC, 104 ± 8 cm). Fatness was measured by DXA and Tanita BC‐418 equipment (Tanita Corp., Tokyo, Japan). Agreement among methods was assessed by Bland‐Altman plots, and regression analysis was used to evaluate anthropometric measures as proxies for total and abdominal fatness. Results: The percentage of overweight subjects was 41.9%, whereas 55.9% of the subjects were obese, as defined by BMI, and all subjects had a WC exceeding the World Health Organization cut‐off point for abdominal obesity. Compared with DXA, the BIA₈ equipment significantly underestimated total %BF (?5.0; ?3.6 to ?8.5 [mean; 95% confidence interval]), fat mass (?3.6; ?3.9 to ?3.2), and tr%BF (?8.5; ?9.1 to ?7.9). The discrepancies between the methods increased with increasing adiposity for both %TBF and tr%BF (both p < 0.001). Variation in BMI explained 28% of the variation in %TBF_DXA and 51% of %TBF_BIA8. Using WC as a proxy for truncal adiposity, it explained only 18% of tr%BF_DXA variance and 27% of tr%BF_BIA8 variance. The corresponding figures for truncal fat mass were 49% and 35%, respectively. No significant age effects were observed in any of the regressions. Discussion: BIA₈ underestimated both total and truncal fatness, compared with DXA, with higher dispersion for tr%BF than %TBF. The discrepancies increased with degree of adiposity, suggesting that the accuracy of BIA is negatively affected by obesity.     

Age variations in the relation of body mass indices to estimates of body fat and muscle mass

In some chronic disease studies, distinctions have been made regarding the importance of body mass index (BMI) as a risk factor in younger versus older men and women. In order to determine the significance of these differences in BMI-disease associations, we determined the extent of age-dependent variations in the relation of BMIs to body composition in large probability samples of U.S. men and women from the First and Second U.S. National Health and Nutrition Examination Surveys (NHANES I and II). BMIs are more highly correlated with estimates of body fat in younger than in older men and women, and with muscle mass in older than in younger adults. Caution should be exercised in interpreting the significance of BMI as a risk factor for chronic disease, particularly in comparison of age groups.