Anatomical patterning of visceral adipose tissue: race, sex, and age variation

Objective: We tested sex, race, and age differences in the patterning of visceral adipose tissue (VAT) and subcutaneous adipose tissue. Research Methods and Procedures: Contiguous 1‐cm‐thick magnetic resonance (MR) images of the abdomen were collected from 820 African‐American and white adults. Repeated‐measures ANOVA was used to examine the effects of image location, sex, race, and age (≥50 vs. <50 years) on adipose tissue areas. Maximum VAT area was identified for each subject from the raw data. Results: Compared to women, men had greater total VAT volume (p < 0.0001), and their maximum VAT area occurred higher in the abdomen (p < 0.0001). Among white men, maximim VAT area most frequently occurred 5 to 10 cm above L4‐L5, whereas in the other groups, maximim VAT area most frequently occurred 1 to 4 cm above L4‐L5 (p < 0.0001). African‐American men had greater total VAT volume than African‐American women (p < 0.01), but this sex difference was only significant using single images cranial to L4‐L5 + 2 cm. Age‐related increases in VAT tended to be greatest 5 to 10 cm above L4‐L5 in men and near L4‐L5 in women. Discussion: A single MR image 5 to 10 cm above L4‐L5 may allow more accurate conclusions than the L4‐L5 image regarding group differences in visceral adiposity.     

Visceral fat, waist circumference, and BMI: impact of race/ethnicity

Objective: BMI and waist circumference are used to define risk from excess body fat. Limited data in women suggest that there may be racial/ethnic differences in visceral adipose tissue (VAT) at a given BMI or waist circumference. This study tested the hypothesis that racial/ethnic differences exist in both men and women in the relationship of anthropometric measures of body composition and computed tomography (CT)‐determined VAT or subcutaneous adipose tissue (SAT). Methods and Procedures: Subjects included 66 African American, 72 Hispanic, and 47 white men and women, aged ≥ 45. Waist circumference and BMI were measured using standard methods. Total abdominal and L4L5 VAT and SAT were measured using CT. Results: Among both men and women, groups did not differ in waist circumference or BMI. White men had greater L4L5 VAT than African‐American men, and both white and Hispanic men had greater total VAT than African‐American men. Among women, Hispanics and whites had greater L4L5 VAT than African Americans, and Hispanics had greater total VAT than African Americans. The slope of the linear relationship between BMI or waist circumference and VAT was lower in African Americans than in Hispanics and/or whites. Discussion: Middle‐aged and older African‐American men and women had lower VAT despite similar BMI and waist circumference measurements. Altered relationships between anthropometric measures and VAT may have implications for defining metabolic risk in different populations. Different waist circumference or BMI cutoff points may be necessary to adequately reflect risk in different racial/ethnic groups.     

Impact of Race/Ethnicity on the Relationship Between Visceral Fat and Inflammatory Biomarkers

The purpose of this study was to determine whether racial/ethnic differences exist in the relationship between visceral adipose tissue (VAT) and selected inflammatory biomarkers. Subjects included 136 African‐American, 133 Hispanic, and 100 white men and women, aged ≥45. Waist circumference and BMI were measured using standard methods. Total VAT, and VAT and subcutaneous adipose tissue (SAT) at the L4L5 spinal level were measured using computed tomography. Interleukin‐6 (IL‐6), C‐reactive protein (CRP), and fibrinogen were measured from fasting blood samples. Results revealed that waist circumference and BMI were similar among groups but African Americans had significantly lower L4L5 VAT compared with Hispanics and whites. Despite lower VAT, African‐American men had similar concentrations of inflammatory biomarkers. On the other hand, African‐American women had higher CRP and IL‐6 than white women, and higher fibrinogen than both Hispanic and white women. After controlling for L4L5 VAT, L4L5 SAT, and age, African‐American women had higher concentrations of IL‐6 and fibrinogen. Stratified analyses for CRP indicated that L4L5 SAT was associated with CRP in African‐American and white women after controlling for L4L5 VAT and age, but that the reverse was not true. These data indicate that African Americans had lower VAT but similar or higher concentrations of inflammatory biomarkers. African‐American women consistently displayed greater inflammation compared with whites, even after controlling for VAT or SAT.     

Apolipoprotein A‐II Polymorphism and Visceral Adiposity in African‐American and White Women

To determine the association between the ?265 T to C substitution in the apolipoprotein A‐II (APOA‐II) gene and levels of visceral adipose tissue (VAT) in a group of premenopausal African‐American and white women, we genotyped 237 women (115 African‐American and 122 white) for this polymorphism. Body composition was assessed by DXA, and VAT was determined from a single computed tomography scan. In addition to VAT, we examined the association between the polymorphism and other phenotypes (total body fat, total abdominal adipose tissue, and subcutaneous abdominal adipose tissue). The mutant C allele in the APOA‐II gene was less frequent in African‐American compared with white women, 23% vs. 36%, respectively (p < 0.01). VAT was significantly higher in carriers of the C allele compared with noncarriers after adjustment for total body fat (p < 0.05). When separate analyses by ethnic group were conducted, the association between the polymorphism and VAT was observed in white (p < 0.05) but not African‐American (p = 0.57) women. There was no association between the polymorphism and the other phenotypes. These results indicate a significant association between the T265C APOA‐II polymorphism and levels of VAT in premenopausal women. This association is present in white but not African‐American women.     

Visceral Adipose Tissue in Women: Longitudinal Study of the Effects of Fat Gain,Time, and Race

Objective: To determine the effects of fat gain, time, and race on the accumulation of visceral adipose tissue (VAT) in a group of normal‐weight premenopausal women. Research Methods and Procedures: Sixty‐five women participated in the study (32 African American and 33 white). The mean age of subjects was 34 ± 6 years (range, 22 to 47 years). Eligible subjects were women who had body mass indices <25 kg/m² at baseline and who had completed evaluations at baseline and at follow‐up year 1, without intervention. A subset of subjects was reevaluated annually for up to 4 years. Body composition was assessed by DXA, and VAT was determined from a single computed tomography scan. A linear mixed model was used to examine changes in VAT over time, with total body fat as a covariate Results: Total fat mass was not significantly different between races at baseline and increased significantly in both groups over time (p < 0.001). Time‐related increases in total body fat were greater in African‐American women (p < 0.01). VAT was significantly higher in white women at baseline (p < 0.01) and increased significantly over time in both races (p < 0.01), but remained higher in white women (p < 0.001). Increases in VAT, relative to total body fat, were greater than the increases in total body fat over time, independent of age and race (p < 0.001). Discussion: Gaining total body‐fat mass results in a higher increase in VAT, relative to total body fat, regardless of race and age, although African‐American women maintain a lower VAT levels across time.     

Larger Amounts of Visceral Adipose Tissue in Asian Americans

Objective: Excess visceral adipose tissue (VAT) is recognized as an important risk factor for the development of coronary heart disease and type 2 diabetes. Several studies have reported less VAT in African Americans compared with whites. As little is known about the levels of VAT in Asians, we compared whole‐body VAT in Asian Americans with European Americans. Research Methods and Procedures: VAT was measured using whole‐body multislice magnetic resonance imaging in 54 women (18 Asian Americans, 36 European Americans) and 53 men (19 Asian Americans, 34 European Americans) with body mass index (measured in kilograms per square meter) < 30. Data were analyzed by multiple regression modeling. Results: Asian American women had higher log‐transformed VAT compared with European American women (p < 0.05), after adjusting for age and total body fat. There was a significant age by race interaction such that race differences in VAT were most evident over the age of 30 years. No differences in VAT could be detected between Asian American and European American men, even after adjusting for potential covariates, including total adiposity. %Discussion: These data are the first to demonstrate higher amounts of VAT in healthy Asian Americans, a finding that suggests normative VAT values or standards derived from whites may not be applicable to Asians.     

Ethnic and sex differences in visceral,subcutaneous, and total body fat in children and adolescents

Objective: This study investigated ethnic and sex differences in the distribution of fat during childhood and adolescence. Design and Methods : A cross‐sectional sample (n = 382), aged 5–18 years, included African American males (n = 84), White males (n = 96), African American females (n = 118), and White females (n = 84). Measures for total body fat (TBF) mass and abdominal adipose tissue (total volume and L4‐L5 cross‐sectional area) for both subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots were assessed by dual‐energy X‐ray absorptiometry and magnetic resonance image, respectively. Analyses of covariance (ANCOVAs) were used to determine ethnic and sex differences in TBF (adjusted for age) and ethnic and sex differences in SAT and VAT (adjusted for both age and TBF). Results: Age‐adjusted TBF was greater in African Americans (P = 0.017) and females (P < 0.0001) compared with Whites and males, respectively. In age‐ and TBF‐adjusted ANCOVAs, no differences were found in the SAT. The VAT volume was, however, greater in Whites (P < 0.0001) and males (P < 0.0001) compared with African Americans and females, respectively. Similar patterns were observed in SAT and VAT area at L4‐L5. Conclusions: The demonstrated ethnic and sex differences are important confounders in the prevalence of obesity and in the assignment of disease risk in children and adolescents.     

Comparison of Regional Fat Distribution and Health Risk Factors in Middle‐Aged White and African American Women: The Healthy Transitions Study

Objective: Both ethnicity and menopause appear to influence intra‐abdominal fat distribution. This study evaluated intra‐abdominal fat distribution and obesity‐related health risks in perimenopausal white and African American women. Research Methods and Procedures: Baseline data from a longitudinal study of changes in body composition and energy balance during menopause are reported. Healthy women (55 African Americans and 103 whites) who were on no medication and had at least five menstrual cycles in the previous 6 months were recruited. Body composition was assessed by DXA, and visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were assessed by computed tomography scan. SAT was divided into deep and superficial layers demarcated by the fascia superficialis. Results: African American women were slightly younger (46.7 ± 0.2 vs. 47.7 ± 0.2 years, p = 0.002) and fatter (42.4% ± 1.0% vs. 39.4% ± 0.8% body fat, p = 0.02) than white women. In unadjusted data, African Americans had significantly more total abdominal fat and total, deep, and superficial SAT than whites. After adjustment for percent body fat and age, only total and superficial SAT remained significantly higher in African Americans. VAT although slightly less in African American women, did not differ significantly by race. In multiple regression analysis, VAT was the strongest predictor of serum lipids, glucose, and insulin in women of both races, although superficial SAT was significantly associated with fasting glucose in whites. Conclusions: Middle‐aged African American women have larger SAT depots, adjusted for total body fatness, but do not differ from white women with regard to VAT. The complexity of the relationship between abdominal fat and metabolic risk is increased by ethnic differences in such associations.     

Both Subcutaneous and Visceral Adipose Tissue Correlate Highly with Insulin Resistance in African Americans

Objective: The contribution of visceral adipose tissue (VAT) to insulin resistance is well‐established; however, the role of subcutaneous abdominal adipose tissue (SAT) in insulin resistance remains controversial. Sex may determine which of these two components of abdominal obesity is more strongly related to insulin resistance and its consequences. The aim of this study was to determine whether both VAT and SAT contribute to insulin resistance in African Americans and to examine the effects of sex on this relationship. Research Methods and Procedures: This was a cross‐sectional study of 78 nondiabetic African‐American volunteers (44 men, 35 women; age 33.8 ± 7.3 years; BMI 30.9 ± 7.4 kg/m²). VAT and SAT volumes were measured using serial computerized tomography slices from the dome of the diaphragm to the iliac crest. The insulin sensitivity index (S_I) was determined from the minimal model using data obtained from the frequently sampled intravenous glucose tolerance test. Results: In men, both VAT and SAT were negatively correlated with S_I (r for both correlations = ?0.57; p < 0.01). In women, the correlation coefficient between VAT and S_I was ?0.50 (p < 0.01) and between SAT and S_I was ?0.67 (p < 0.01). In women, the correlation coefficient for S_I with SAT was significantly greater than the correlation coefficient with VAT (p = 0.02). Discussion: Both SAT and VAT are strongly correlated with insulin resistance in African Americans. For African‐American women, SAT may have a greater effect than VAT on insulin resistance.     

Femoral-gluteal subcutaneous and intermuscular adipose tissues have independent and opposing relationships with CVD risk.

Femoral-gluteal adipose tissue (AT) may be cardioprotective through fatty acids uptake. Femoral-gluteal AT has previously been defined as leg fat measured by dual energy x-ray absorptiometry (DXA); however, subcutaneous adipose tissue (SAT) and intermuscular adipose tissue (IMAT) are inseparable using DXA. This study investigated the independent relationships between femoral-gluteal SAT, femoral-gluteal IMAT, and cardiovascular disease (CVD) risk factors [fasting serum measures of glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDLC), triglycerides (TG) and insulin] and whether race differences exist in femoral-gluteal AT distribution. Adult Caucasians (56 men and 104 women), African-Americans (37 men and 76 women), and Asians (11 men and 35 women) had total AT (TAT) including femoral-gluteal AT (upper leg SAT and IMAT) and visceral AT (VAT) by magnetic resonance imaging (MRI). General linear models identified the independent effects of femoral-gluteal SAT and femoral-gluteal IMAT on each risk factor after covarying for TAT, VAT, age, race, sex, and two-way interactions. Femoral-gluteal IMAT and glucose (P < 0.05) were positively associated independent of VAT. There were also significant inverse associations between femoral-gluteal SAT and insulin (P < 0.01) and TG (P < 0.05), although the addition of VAT rendered these effects nonsignificant, possibly due to collinearity. Asian women had less femoral-gluteal SAT and greater VAT than Caucasians and African-Americans (P < 0.05) and Asian and African-American men had greater femoral-gluteal IMAT than Caucasians, adjusted for age and TAT (P < 0.05 for both). Femoral-gluteal SAT and femoral-gluteal IMAT distribution varies by sex and race, and these two components have independent and opposing relationships with CVD risk factors.     

Serum Leptin in Elderly People: Associations with Sex Hormones,Insulin, and Adipose Tissue Volumes

BAUMGARTNER, RICHARD N., ROBERT R. ROSS, DEBRA L. WATERS, WILLIAM M. BROOKS, JOHN E. MORLEY, GEORGE D. MONTOYA, AND PHILIP J. GARRY. Serum leptin in elderly people: associations with sex hormones, insulin, and adipose tissue volumes. Obes Res. Objective There are few data for associations of serum leptin with body fat, fat distribution, sex hormones, or fasting insulin in elderly adults. We hypothesized that the sex difference in serum leptin concentrations would disappear after adjustment for subcutaneous, but not visceral body fat. Serum leptin would not be associated with sex hormone concentrations or serum fasting insulin after adjusting for body fat and fat distribution. Research Methods and Procedures Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes were measured using magnetic resonance imaging in a cross-sectional sample of 56 nondiabetic, elderly men and women aged 64 years to 94 years. Serum leptin, sex hormones (testosterone and estrone), sex hormone-binding globulin, and fasting insulin were also measured. Nine women were taking hormone replacement, and five men were clinically hypogonadal. Results Leptin was significantly associated with both SAT and VAT in each sex. Adjustment for SAT reduced the sex difference in leptin by 56%, but adjustment for VAT increased the difference by 25%. Leptin was not associated with serum estrone or hormone replacement therapy in the women, but had a significant, negative association with testosterone in the men that was independent of SAT, but not VAT. Leptin was significantly associated with fasting insulin in both sexes independent of age, sex hormones, sex hormone-binding globulin, VAT and SAT. Discussion Sex difference in serum leptin is partly explained by different amounts of SAT. Studies including both men and women should adjust for SAT rather than total body fat that includes VAT. The sex difference in serum leptin is not due to estrogen, but may be partly explained by testosterone. Testosterone is negatively associated with leptin in men, but the association is confounded with VAT. Leptin is associated with fasting insulin in non-diabetic elderly men and women independent of body fat, fat distribution. or sex hormones.     

Ethnic Differences in Visceral Adipose Tissue and Type 2 Diabetes: Filipino,African‐American,and White Women

Objective: To compare ethnic differences in visceral adipose tissue (VAT), assessed by computed tomography, and type 2 diabetes risk among 55‐ to 80‐year‐old Filipino, African‐American, and white women without known cardiovascular disease. Research Methods and Procedures: Subjects were participants in the Rancho Bernardo Study (n = 196), the Filipino Women's Health Study (n = 181), and the Health Assessment Study of African‐American Women (n = 193). Glucose and anthropometric measurements were assessed between 1995 and 2002. Results: African‐American women had significantly higher age‐adjusted BMI (29.7 kg/m²) and waist girth (88.1 cm) compared with Filipino (BMI, 25.5 kg/m²; waist girth, 81.9 cm) or white (BMI: 26.0 kg/m²; waist girth: 80.7 cm) women. However, VAT was significantly higher among Filipino (69.1 cm³) compared with white (62.3 cm³; p = 0.037) or African‐American (57.5 cm³, p < 0.001) women. VAT correlated better with BMI (r = 0.69) and waist (r = 0.77) in whites, compared with Filipino (r = 0.42; r = 0.59) or African‐American (r = 0.50; r = 0.56) women. Age‐adjusted type 2 diabetes prevalence was significantly higher in Filipinas (32.1%) than in white (5.8%) or African‐American (12.1%) women. Filipinas had higher type 2 diabetes risk compared with African Americans [adjusted odds ratio, 2.30; 95% confidence interval (CI), 1.09 to 4.86] or whites (adjusted odds ratio, 7.51; 95% CI, 2.51 to 22.5) after adjusting for age, VAT, exercise, education, and alcohol intake. Discussion: VAT was highest among Filipinas despite similar BMI and waist circumference as whites. BMI and waist circumference were weaker estimates of VAT in Filipino and African‐American women than in whites. Type 2 diabetes prevalence was highest among Filipino women at every level of VAT, but VAT did not explain their elevated type 2 diabetes risk.     

Obesity and C-reactive protein levels among white, black, and hispanic US adults

Objective: Studies suggest that obesity's adverse impact on cardiovascular mortality may be reduced in African Americans relative to white Americans. We examined whether obesity's association with novel cardiovascular risk factors such as C‐reactive protein (CRP) also varies by race and ethnicity. Methods and Procedures: We analyzed data from 10,492 white, African‐American, and Hispanic‐American participants of the 1999–2004 National Health and Nutrition Examination Survey, who were aged 20 years and older, with a BMI ≥18.5 kg/m² and CRP ≤10 mg/l. We fit sex‐specific multivariable models of the association of BMI or waist circumference with log CRP levels and tested for interactions of BMI or waist circumference with race/ethnicity. Results: Higher BMI was significantly associated with higher CRP in all racial/ethnic groups for both men and women (P > 0.05 for BMI–race/ethnicity interaction) before and after adjustment for age, education, and health behaviors. Larger waist circumference was also associated with higher CRP levels in all racial/ethnic groups before and after adjustment; among women, the relationship was strongest for Mexican Hispanics (P < 0.01 for waist circumference–race/ethnicity interaction). Results were similar after additional adjustment for medications that might affect CRP levels. Discussion: The association between obesity and CRP is at least as strong in African Americans and Hispanic Americans as in white Americans. Racial differences in the relationship between obesity and cardiovascular mortality are unlikely to be due to racial differences in obesity's impact on CRP.     

The relationship of waist circumference and BMI to visceral, subcutaneous, and total body fat: sex and race differences

The purpose of this study was to examine sex and race differences in the relationship between anthropometric measurements and adiposity in white and African-American (AA) adults. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) areas were measured with computed tomography (CT). Fat mass (FM) was measured with dual-energy-X-ray absorptiometry (DXA). Correlation coefficients were used to assess the relationship of waist circumference (WC) and BMI to VAT, SAT, and FM within sex-by-race groups. General linear models were used to compare relationships between WC or BMI, and adiposity across sex and race, within age groups (18-39 and 40-64 years). The sample included 1,667 adults (men: 489 white; 120 AA; women: 666 white, 392 AA). WC and BMI correlations were highest for FM and SAT compared to VAT. Women had higher FM levels than men regardless of WC, but the sex difference in FM was attenuated in younger AA adults with a high BMI. For a given level of WC or BMI, women had higher levels of SAT than men; however, significant interactions indicated that the relationship was not consistent across all levels of BMI and WC. Sex and race differences in VAT varied significantly with WC and BMI. In general, white adults had higher levels of VAT than AA adults at higher levels of BMI and WC. Sex differences, and in some instances race differences, in the relationships between anthropometry and fat-specific depots demonstrate that these characteristics need to be considered when predicting adiposity from WC or BMI.     

Differences in Resting Metabolic Rate between White and African‐American Young Adults

Objective: A reported lower resting metabolic rate (RMR) in African‐American women than in white women could explain the higher prevalence of obesity in the former group. Little information is available on RMR in African‐American men. Research Methods and Procedures: We assessed RMR by indirect calorimetry and body composition by DXA in 395 adults ages 28 to 40 years (100 African‐American men, 95 white men, 94 African‐American women, and 106 white women), recruited from participants in the Coronary Artery Risk Development in Young Adults (CARDIA), Birmingham, Alabama, and Oakland, California, field centers. Results: Using linear models, fat‐free mass, fat mass, visceral fat, and age were significantly related to RMR, but the usual level of physical activity was not. After adjustment for these variables, mean RMR was significantly higher in whites (1665.07 ± 10.78 kcal/d) than in African Americans (1585.05 ± 11.02 kcal/d) by 80 ± 16 kcal/d (p < 0.0001). The ethnic × gender interaction was not significant (p = 0.9512), indicating that the difference in RMR between African‐American and white subjects was similar for men and women. Discussion: RMR is ～5% higher in white than in African‐American participants in CARDIA. The difference was the same for men and women and for lean and obese individuals. The prevalence of obesity is not higher in African‐American men than in white men. Because of these reasons, we believe that RMR differences are unlikely to be a primary explanation for why African‐American women are more prone to obesity than white women.     

Associations of Fat Distribution and Obesity with Hypertension in a Bi‐ethnic Population: The ARIC Study

Objective: To examine associations of hypertension with obesity and fat distribution among African American and white men and women. Research Methods and Procedures: The analysis sample included 15,063 African American and white men and women between the ages of 45 and 64 years who were participants in the 1987 through 1989 examination of the Atherosclerosis Risk in Communities Study (ARIC). Odds ratios and adjusted prevalences of hypertension were calculated across sexspecific quintiles of body mass index (BMI), waist‐to‐hip ratio (WHR), waist circumference, and waist‐to‐height ratio (waist/height) and adjusted for age, research center, smoking, education, physical activity, alcohol consumption, hormone replacement therapy, and menopausal status. Results: The prevalence of hypertension was higher among African Americans than whites. In the lowest quintile of BMI, 41% of African American women and 43% of African American men had hypertension compared with 14% of white women and 19% of white men. Elevated BMI, WHR, waist circumference, and waist/height were associated with increased odds of hypertension in African American and white men and women. In women, but not in men, there were significant interactions between ethnicity and the anthropometric variables studied here. The direction of the interaction indicated larger odds ratios for hypertension with increasing levels of anthropometric indices in white compared with African American women. Discussion: Obesity and abdominal fat preponderance were associated with increased prevalence of hypertension in African American and white men and women. Associations were similar among African American and white men, but obesity and fat patterning were less strongly associated with hypertension in African American than in white women.     

Waist Circumference,BMI, and Visceral Adipose Tissue in White Women and Women of African Descent

Although waist circumference (WC) is a marker of visceral adipose tissue (VAT), WC cut‐points are based on BMI category. We compared WC‐BMI and WC‐VAT relationships in blacks and whites. Combining data from five studies, BMI and WC were measured in 1,409 premenopausal women (148 white South Africans, 607 African‐Americans, 186 black South Africans, 445 West Africans, 23 black Africans living in United States). In three of five studies, participants had VAT measured by computerized tomography (n = 456). Compared to whites, blacks had higher BMI (29.6 ± 7.6 (mean ± s.d.) vs. 27.6 ± 6.6 kg/m², P = 0.001), similar WC (92 ± 16 vs. 90 ± 15 cm, P = 0.27) and lower VAT (64 ± 42 vs. 101 ± 59 cm², P < 0.001). The WC‐BMI relationship did not differ by race (blacks: β (s.e.) WC = 0.42 (.01), whites: β (s.e.) WC = 0.40 (0.01), P = 0.73). The WC‐VAT relationship was different in blacks and whites (blacks: β (s.e.) WC = 1.38 (0.11), whites: β (s.e.) WC = 3.18 (0.21), P < 0.001). Whites had a greater increase in VAT per unit increase in WC. WC‐BMI and WC‐VAT relationships did not differ among black populations. As WC‐BMI relationship did not differ by race, the same BMI‐based WC guidelines may be appropriate for black and white women. However, if WC is defined by VAT, race‐specific WC thresholds are required.     

Racial Differences in Insulin Secretion and Sensitivity in Prepubertal Children: Role of Physical Fitness and Physical Activity

Objective: To investigate in prepubertal children whether physical fitness and/or physical activity are: 1) associated with insulin secretion and sensitivity and 2) account for racial differences in insulin secretion and sensitivity. Research Methods and Procedures: Subjects included 34 African American and 34 white nondiabetic children aged 5 to 11 years. Data were divided into two sets according to the availability of VO_2max and physical activity data. Body composition was measured by dual‐energy X‐ray absorptiometry. Subcutaneous abdominal adipose tissue and intra‐abdominal adipose tissue were examined by computed tomography. Insulin sensitivity (S_I) and acute insulin response (AIR) were determined by a frequently sampled intravenous glucose tolerance test. An all‐out, progressive treadmill exercise test was used for measuring VO_2max. Physical activity data were collected by questionnaire. Results: African American children had lower S_I and higher AIR than white children, after adjusting for total body fat mass. African Americans reported higher levels of physical activity (hours/wk) than whites, but had a lower VO_2max. In multiple linear regression analysis, hours/wk of activity and hours/wk of vigorous activity, but not moderate activity, were independently related to S_I and AIR after adjusting for race, total body fat mass or fat distribution, and total lean tissue mass. VO_2max was not related to AIR, and was inversely related to S_I, after adjusting for body composition. Race remained significantly associated with both S_I and AIR, even after adjusting for body composition, fat distribution, and hours/wk of activity or hours/wk of vigorous activity. Discussion: In summary, overall physical activity and, especially, vigorous activity were associated with insulin secretion and sensitivity. However, neither physical activity nor VO_2max explained the racial difference in insulin secretion (higher in African Americans) and sensitivity (lower in African Americans). Thus, racial (African American to white) differences in aspects of insulin action seem to be due to factors other than body composition, fat distribution, cardiovascular fitness, and amount of physical activity.     

Racial Differences in Insulin Resistance and Mid‐Thigh Fat Deposition in Postmenopausal Women

Objective: To determine whether racial differences in insulin resistance between African American (AA) and white women exist in postmenopausal women and whether they are related to physical fitness and/or obesity. Research Methods and Procedures: We studied 35 obese AA (n = 9) and white (n = 26) women of comparable maximal oxygen consumption, obesity, and age. Total body fat was measured by DXA. Abdominal and mid‐thigh low‐density lean tissue (a marker of intramuscular fat) were determined with computed tomography. Glucose utilization (M) was measured during the last 30 minutes of a 3‐hour hyperinsulinemic‐euglycemic clamp. Insulin sensitivity was estimated from the relationship of M to the concentration of insulin during the last 30 minutes of the clamp. Results: The percentage of fat and total body fat mass were similar between AA and white women, whereas fat‐free mass was higher in African American women. Visceral adipose tissue was not different between groups, but subcutaneous abdominal fat was 17% higher in the AA than in the white women. AA women had an 18% greater mid‐thigh muscle area (p < 0.01) and a 34% greater mid‐thigh low‐density lean tissue area than the white women. Fasting glucose concentrations were not different, but fasting insulin concentrations were 29% higher in AA women. Glucose utilization was 60% lower in the AA women because of a lower non‐oxidative glucose disposal. Insulin sensitivity was 46% lower in the AA women. Discussion: AA postmenopausal women have more mid‐thigh intramuscular fat, lower glucose utilization, and are less insulin sensitive than white women despite comparable fitness and relative body fat levels.     

Racial and ethnic differences in perceptions of discrimination among Muslim Americans

I use data from the 2011 Pew Survey (N?=?1,033) to examine the prevalence and correlates of perceived discrimination across Muslim American racial/ethnic groups. Asian Muslims report the lowest frequency of perceived discrimination than other Muslim racial/ethnic groups. Nearly, all Muslim racial/ethnic groups have a few times higher odds of reporting one or more types of perceived discrimination than white Muslims. After controlling for socio-demographic characteristics, the observed relationships persist for Hispanic Muslims but disappear for black and other/mixed race Muslims. Women are less likely than men to report several forms of discrimination. Older Muslims report lower rates of perceived discrimination than younger Muslims. White Muslim men are more likely to report experiencing discrimination than white, black and Asian Muslim women. The findings highlight varying degrees of perceived discrimination among Muslim American racial/ethnic groups and suggest examining negative implications for Muslims who are at the greatest risk of mistreatment.