Revisiting the United States Army body composition standards: a receiver operating characteristic analysis.

BACKGROUND: The objective for percent body fat standards in the United States Army Body Composition Program (ABCP) is to ensure soldiers maintain optimal well-being and performance under all conditions. However, conducting large-scale experiments within the United States Army to evaluate the efficacy of the thresholds is challenging. METHODS: A receiver operating characteristic (ROC) analysis with corresponding area under the curve (AUC) was performed on body mass index (BMI) and waist circumference to determine optimal gender-specific age cohort thresholds that meet ABCP percent body fat standards in the National Health and Nutrition Examination Survey (NHANES) III. A second dataset consisting of a cohort of basic training recruits (N = 20,896 soldiers, 28% female) with BMI and waist circumference measured using a 3D body image scanner was applied to calculate what percent of basic training recruits meet the ABCP percent body fat standards. Regression models to determine the contribution of different circumference sites to the predictions of percent body fat were developed using a database compiled at the New York Obesity Research Center (N = 500). RESULTS: Optimal BMI thresholds ranged from 23.65 kg/m2 (17-21-year-old cohort) to 26.55 kg/m2 (40 and over age cohort) for males and 21.75 to 24.85 kg/m2 for females. The AUC values were between 0.86 and 0.92. The waist circumference thresholds ranged 81.35 to 97.55 cm for males and 77.05 to 89.35 cm for females with AUC values between 0.90 and 0.91. These BMI thresholds were exceeded by 65% of male and 74% of female basic training recruits and waist circumference thresholds were exceeded by 73% of male and 85% of female recruits. The single circumference that contributed most to prediction of body fat was waist circumference in males and mid-thigh circumference in females. CONCLUSIONS: The ABCP percent body fat thresholds yield BMI thresholds that are below the United States Army BMI standards, especially in females which suggests the ABCP percent body fat standards may be too restrictive. The United States Army percent body fat standards could instead be matched to existing national health guidelines.

Development and reproducibility of a computed tomography-based measurement of renal sinus fat.

BACKGROUND: Renal sinus fat may mediate obesity-related vascular disease, although this fat depot has not been assessed in a community-based sample. We sought to develop a protocol to quantify renal sinus fat accumulation using multi-detector computed tomography (MDCT). METHODS: Protocol development was performed in participants in the Framingham Offspring cohort who underwent MDCT. Volumetric renal sinus fat was measured separately within the right and left kidneys, and renal sinus fat area within a single MDCT scan slice was measured in the right kidney. Due to the high correlation of volumetric and single-slice renal sinus fat in the right kidney (Pearson correlation [r] = 0.85, p < 0.0001), we optimized a single-slice protocol to capture renal sinus fat in the right kidney alone. Pearson correlation coefficients were used to compare to assess the correlation of volumetric and single-slice renal sinus fat in the right kidney with other measures of adiposity. Inter- and intra-reader reproducibility was assessed using intra-class correlation coefficients. RESULTS: Single-slice measurements were obtained in 92 participants (mean age 60 years, 49% women, median renal sinus fat 0.43 cm2). Intra- and inter-reader intra-class correlation coefficients were 0.93 and 0.86, respectively. Single-slice renal sinus fat was correlated with body mass index (r = 0.35, p = 0.0006), waist circumference (r = 0.31, p = 0.003), and abdominal visceral fat (r = 0.48, p < 0.0001). Similar correlations were observed for volumetric renal sinus fat in the right kidney. CONCLUSIONS: Measuring renal sinus fat is feasible and reproducible using MDCT scans in a community-based sample.

Topography mapping of whole body adipose tissue using A fully automated and standardized procedure.

PURPOSE: To obtain quantitative measures of human body fat compartments from whole body MR datasets for the risk estimation in subjects prone to metabolic diseases without the need of any user interaction or expert knowledge. MATERIALS AND METHODS: Sets of axial T1-weighted spin-echo images of the whole body were acquired. The images were segmented using a modified fuzzy c-means algorithm. A separation of the body into anatomic regions along the body axis was performed to define regions with visceral adipose tissue present, and to standardize the results. In abdominal image slices, the adipose tissue compartments were divided into subcutaneous and visceral compartments using an extended snake algorithm. The slice-wise areas of different tissues were plotted along the slice position to obtain topographic fat tissue distributions. RESULTS: Results from automatic segmentation were compared with manual segmentation. Relatively low mean deviations were obtained for the class of total tissue (4.48%) and visceral adipose tissue (3.26%). The deviation of total adipose tissue was slightly higher (8.71%). CONCLUSION: The proposed algorithm enables the reliable and completely automatic creation of adipose tissue distribution profiles of the whole body from multislice MR datasets, reducing whole examination and analysis time to less than half an hour.

Body fat reference curves for healthy Turkish children and adolescents.

UNLABELLED: Childhood obesity is a major worldwide health problem. In addition to body mass index (BMI), body fat percentiles may be used to predict future cardiovascular and metabolic health risks. The aim of this study is to define new age- and gender-specific body fat centiles for Turkish children and adolescents. A total of 4,076 (2,276 girls, 1,800 boys) children and adolescents aged 6-18 years were recruited for this study. Total body fat was measured by a bioelectrical impedance noninvasive method. Body fat percentiles were produced by the LMS method. The body fat percentile curves of boys appear to rise from age 6 to 12 years and then slope downwards to age 15 years and then flatten off. The body fat % percentiles of girls increased until 14 years of age through 75th to 97th percentiles and then slope downwards, but through the third to 50th percentiles, they showed a downward slope after 14 years old. CONCLUSIONS: Since BMI may not always reflect body fat content, direct assessment of adiposity by a practical method would be significantly useful for clinical decisions. Therefore, this study provides normative data for body fat percentage in healthy Turkish children and adolescents. To this goal we used a practical and clinically applicable method. These references can be useful for evaluation of overweight and obesity.

Measurement of mean subcutaneous fat thickness: eight standardised ultrasound sites compared to 216 randomly selected sites.

Ultrasound (US) provides the most accurate technique for thickness measurements of subcutaneous adipose tissue (SAT) layers. This US method was recently standardised using eight sites to capture SAT patterning and allows distinguishing between fat and embedded fibrous structures. These eight sites chosen for fat patterning studies do not represent the mean SAT thickness measured all over the body that is necessary for determining subcutaneous fat mass. This was obtained by SAT measurements at 216 sites distributed randomly all over the body. Ten participants with BMI below 28.5kgm-2 and SAT means (from eight sites) ranging from 3 mm to 10 mm were selected. The means from eight sites overestimated the means obtained from 216 sites (i.e. 2160 US measurements in the ten participants); the calibration factor of 0.65 corrects this; standard deviation (SD) was 0.05, i.e. 8%. The SD of the calibration factor transforms linearly when estimating the error range of the whole body's SAT volume (body surface area times the calibrated mean SAT thickness). The SAT masses ranged from 3.2 to 12.4 kg in this group. The standard deviations resulting from solely the calibration factor uncertainty were ±0.3 and ±1.0 kg, respectively. For these examples, the SAT percentages were 4.9(±0.4)% and 13.3(±1.0)%.

Index of central obesity - A novel parameter.

Waist circumference (WC) is globally used as a parameter to quantify central obesity, the key culprit in insulin resistance and related disorders. Hitherto globally in various definitions of metabolic syndrome and risk scores, WC is used to quantify central obesity. For defining central obesity, which is a single entity numerous WC cutoffs have been suggested, separately for males and females and various races. We believe that this difference is amenable to differences in their average heights. To quantify proportion of visceral fat in the total body fat, WC alone is not sufficient. We hereby hypothesize that Index of central obesity (ICO) defined by us, as a ratio of WC and height is a better parameter of central obesity. If ICO is used in place of WC we may do away with various WC cutoffs and may have a single cutoff applicable to all races and both genders. Using average heights of various countries and their respective WC cutoffs suggested by IDF consensus definition for defining metabolic syndrome (MS) we derived their ICO cutoffs mathematically. The ICO cutoffs obtained ranged from 0.51 to 0.58 among males and 0.47 to 0.54 among females. The range has narrowed down compared to wide range of cutoffs for WC i.e. 90-102 cm for males and 80-88 cm for females. To test superiority of ICO over WC even among people of same race and same gender we conducted a pilot study in which, we compared two subjects with same WC and body mass index (BMI), though they differed in their stature. Body fat distribution was compared on DEXA and oral glucose tolerance was tested. Percentage of total body fat contributed by truncal fat was 36.11% in taller subject (Dr. P) and 46.31% in the shorter one (Mr. P). On investigation Dr P had normal glucose tolerance while Mr. P was diagnosed to be diabetic. These differences unexplained by identical WC and BMI could be explained by difference in their ICO (0.557 vs 0.645). ICO has a potential to be a better parameter of central obesity. It may obviate the need for numerous WC cutoffs and may even be applicable to children where existing parameters are not useful.

Ethnic-specific body mass index cut-off points for overweight and obesity in girls.

AIM: To develop ethnic-specific body mass index (BMI) cut-off points for overweight and obesity in girls from New Zealand's five major ethnic groups. METHODS: A total of 1676 girls (41% European, 21% Pacific Island, 15% East Asian, 13% Maori, and 11% South Asian) aged 5-16 years participated in this study. BMI was determined from height and weight, and body fat percentage (%BF) was obtained from hand-to-foot bioelectrical impedance measurements. Using stepwise multiple regression, a series of ethnic-specific BMI cut-off points were developed that corresponded to the equivalent %BF of European girls at the BMI reference values provided by the International Obesity TaskForce (IOTF). RESULTS: The adjusted cut-off points for overweight and obesity ranged from an average of 3.3 and 3.8 kg.m(-2) (respectively) lower than the IOTF standards in South Asian girls to 1.5 and 1.9 kg.m(-2) higher in Pacific Island girls. CONCLUSION: We conclude that the ethnic-specific BMI cut-off points developed in this study are more appropriate than universal definitions of overweight and obesity for predicting excess adiposity in New Zealand girls.

Similarity in percent body fat between white and Vietnamese women: implication for a universal definition of obesity.

It has been widely assumed that for a given BMI, Asians have higher percent body fat (PBF) than whites, and that the BMI threshold for defining obesity in Asians should be lower than the threshold for whites. This study sought to test this assumption by comparing the PBF between US white and Vietnamese women. The study was designed as a comparative cross-sectional investigation. In the first study, 210 Vietnamese women ages between 50 and 85 were randomly selected from various districts in Ho Chi Minh City (Vietnam). In the second study, 419 women of the same age range were randomly selected from the Rancho Bernardo Study (San Diego, CA). In both studies, lean mass (LM) and fat mass (FM) were measured by dual-energy X-ray absorptiometry (DXA) (QDR 4500; Hologic). PBF was derived as FM over body weight. Compared with Vietnamese women, white women had much more FM (24.8 +/- 8.1 kg vs. 18.8 +/- 4.9 kg; P < 0.0001) and greater PBF (36.4 +/- 6.5% vs. 35.0 +/- 6.2%; P = 0.012). However, there was no significant difference in PBF between the two groups after matching for BMI (35.1 +/- 6.2% vs. 35.0 +/- 5.7%; P = 0.87) or for age and BMI (35.6 +/- 5.1% vs. 35.8 +/- 5.9%; P = 0.79). Using the criteria of BMI >or=30, 19% of US white women and 5% of Vietnamese women were classified as obese. Approximately 54% of US white women and 53% of Vietnamese women had their PBF >35% (P = 0.80). Although white women had greater BMI, body weight, and FM than Vietnamese women, their PBF was virtually identical. Further research is required to derive a more appropriate BMI threshold for defining obesity for Asian women.

Body fat distribution reference standards in Spanish adolescents: the AVENA Study.

OBJECTIVE: To present body fat patterning reference standards to identify children with a predominant distribution of body fat in the abdominal or truncal region of the body. DESIGN: Cross-sectional study in a representative sample of Spanish adolescents aged 13-18 years. SUBJECTS: A total of 2160 adolescents with a complete set of anthropometric measurements (1109 males and 1051 females). MEASUREMENTS: Weight, height, body mass index, skinfold thickness (biceps, triceps, subscapular, suprailiac, thigh, calf) and waist and hip circumferences. RESULTS: In the majority of the age groups, subscapular/triceps skinfolds ratio, trunk-to-total skinfolds percent (TTS%)and waist circumference values were significantly higher in males than in females; hip circumference was higher in females than in males, except at 15.5 years. In males, age showed a significant effect for all the body fat distribution indices; however, in females, the effect was only significant for triceps skinfold, waist and hip circumferences and waist-to-hip ratio. Smoothed age- and sex-specific triceps skinfold, subscapular skinfold, subscapular/triceps skinfolds ratio, TTS%, waist circumference and hip circumference, waist-to-hip and waist-to-height ratio percentile values for male and female adolescents have been established. CONCLUSION: These reference data for waist circumference and the other fat patterning indices, together with data from other countries, will help to establish international central obesity criteria for adolescents. The presented percentile values will give the possibility to estimate the proportion of adolescents with high or low regional adiposity amounts.