Black women have smaller abdominal girths than white women of the same relative weight

Visual Representation of Body Shape in African-American and European American Women: Clinical Considerations

BACKGROUND

Body mass index (BMI) has been used widely among clinicians to assess obesity in their patients due to its ease and availability. However, BMI has some diagnostic limitations and other measures related to health risks; in particular, body shape may be of greater relevance to health outcomes.

OBJECTIVE

The objective of this study was to illustrate the importance of body shape assessments above and beyond BMI and its relationship to health risk among a sample of African-American and European American women.

METHODS

African-American and European American women aged 19–78 years (n = 552) in Birmingham, Alabama, were recruited and stratified by menopausal status (ie, pre- or postmenopausal). Pictorial body shapes were derived from digital photographs, while body fat distribution defined by android–gynoid ratio (AGR) and body composition were obtained from dual-energy X-ray absorptiometry.

RESULTS

Images of BMI and age-matched women illustrate variability in fat distribution. Among both menopausal status groups, more than 50% of women had a pear body shape (AGR < 1). An apple body shape was associated with higher odds of having diabetes (unadjusted odds ratio [OR]: 4.1, 95% confidence interval [CI]: 1.9–9.3), hypertension (unadjusted OR: 3.1, 95% CI: 2.0–4.7), and high cholesterol (unadjusted OR: 3.0, 95% CI: 1.8–5.1).

CONCLUSION

Use of visual cues alongside traditional methods of weight status assessment may help to facilitate weight management conversations between physicians and female patients. However, next steps should include the validation of visual assessments of body shape in women for use by physicians.

A practical genome scan for population-specific strong selective sweeps that have reached fixation

Phenotypic divergences between modern human populations have developed as a result of genetic adaptation to local environments over the past 100,000 years. To identify genes involved in population-specific phenotypes, it is necessary to detect signatures of recent positive selection in the human genome. Although detection of elongated linkage disequilibrium (LD) has been a powerful tool in the field of evolutionary genetics, current LD-based approaches are not applicable to already fixed loci. Here, we report a method of scanning for population-specific strong selective sweeps that have reached fixation. In this method, genome-wide SNP data is used to analyze differences in the haplotype frequency, nucleotide diversity, and LD between populations, using the ratio of haplotype homozygosity between populations. To estimate the detection power of the statistics used in this study, we performed computer simulations and found that these tests are relatively robust against the density of typed SNPs and demographic parameters if the advantageous allele has reached fixation. Therefore, we could determine the threshold for maintaining high detection power, regardless of SNP density and demographic history. When this method was applied to the HapMap data, it was able to identify the candidates of population-specific strong selective sweeps more efficiently than the outlier approach that depends on the empirical distribution. This study, confirming strong positive selection on genes previously reported to be associated with specific phenotypes, also identifies other candidates that are likely to contribute to phenotypic differences between human populations.

Associations of abdominal fat with perceived racism and passive emotional responses to racism in African American women

OBJECTIVES

An excess in abdominal fat may predispose African American women to chronic health conditions such as diabetes and cardiovascular disease. Because stress may increase body fat in the center-body region, we used the waist-to-hip ratio (WHR) to examine associations between excess abdominal fat and perceived racism (a chronic stressor) and daily stress. Passive emotional responses to perceived racism, hypothesized to have particularly adverse effects, were also examined.

METHODS

We controlled for body mass index in multiple logistic regression models among 447 African American women who completed a telephone interview on perceived racism.

RESULTS

Passive emotional responses were not related to WHR (odds ratio [OR]=1.4; 95% confidence interval [CI]=0.8, 2.4). High perceived racism was associated with a low WHR in this population (OR=0.4; 95% CI=0.3, 0.8). However, high daily stress was related to a high WHR (OR=2.7; 95% CI=1.1, 6.7).

CONCLUSIONS

Findings support an association between daily stress and WHR but do not support our hypothesis that passive emotional responses to perceived racism increase abdominal fat. Further study of the stress physiology of perceived racism in African American women is warranted.

Comparison of abdominal adiposity and overall obesity in predicting risk of type 2 diabetes among men

BACKGROUND

Obesity is a strong risk factor for type 2 diabetes. However, few studies have compared the predictive power of overall obesity with that of central obesity. The cutoffs for waist circumference (WC) and waist-to-hip ratio (WHR) as measures of abdominal adiposity remain controversial.

OBJECTIVE

The objective was to compare body mass index (BMI), WC, and WHR in predicting type 2 diabetes.

DESIGN

A prospective cohort study (Health Professionals Follow-Up Study) of 27 270 men was conducted. WC, WHR, and BMI were assessed at baseline. Covariates and potential confounders were assessed repeatedly during the follow-up.

RESULTS

During 13 y of follow-up, we documented 884 incident type 2 diabetes cases. Age-adjusted relative risks (RRs) across quintiles of WC were 1.0, 2.0, 2.7, 5.0, and 12.0; those of WHR were 1.0, 2.1, 2.7, 3.6, and 6.9; and those of BMI were 1.0, 1.1, 1.8, 2.9, and 7.9 (P for trend < 0.0001 for all). Multivariate adjustment for diabetes risk factors only slightly attenuated these RRs. Adjustment for BMI substantially attenuated RRs for both WC and WHR. The receiver operator characteristic curve analysis indicated that WC and BMI were similar and were better than WHR in predicting type 2 diabetes. The cumulative proportions of type 2 diabetes cases identified according to medians of BMI (>/=24.8), WC (>/=94 cm), and WHR (>/=0.94) were 82.5%, 83.6%, and 74.1%, respectively. The corresponding proportions were 78.9%, 50.5%, and 65.7% according to the recommended cutoffs.

CONCLUSIONS

Both overall and abdominal adiposity strongly and independently predict risk of type 2 diabetes. WC is a better predictor than is WHR. The currently recommended cutoff for WC of 102 cm for men may need to be reevaluated; a lower cutoff may be more appropriate.

Ethnic-specific revisions of body mass index cutoffs to define overweight and obesity in Asians are not warranted

Studies showing that Asians with a body mass index (BMI) at the high end of the 'normal' range are at increased risk of disease do not justify a different definition of obesity for that ethnic group without comparable data from Caucasians showing no similar increase in risk. The current BMI cutpoints for obesity are somewhat arbitrary, but there is value in a simple, uniform definition across populations. It seems prudent to separate the scientific construct of obesity from the politically linked, nationally specific BMI cutpoint used to trigger public health or clinical action.

Sensitivity and specificity of anthropometrics for the prediction of diabetes in a biracial cohort

OBJECTIVE

To evaluate the ability of body mass index, waist circumference, waist-to-hip ratio, and combinations of these variables to discriminate individuals who will develop diabetes in adulthood.

RESEARCH METHODS AND PROCEDURES

Data were from 45- to 64-year-old men and women who were members of the Atherosclerosis Risk in Communities cohort. The analysis sample consisted of 12,814 African American and white participants who were free of diabetes at baseline. Body mass index, waist circumference, waist-to-hip ratio, and diabetes incidence (defined as one glucose measure > or =126 mg/dL after fasting for at least 8 hours, one nonfasting glucose measure > or =200 mg/dL, and self-report of diabetes or report of taking medication for diabetes).

RESULTS

1515 new cases of diabetes were identified over the 9-year follow-up. Areas under receiver operating characteristic curves ranged from 0.66 to 0.73 for single measures. The curves were smooth, with no indication of a threshold. Waist tended to have the highest receiver operating characteristic statistic in all groups, but differences were small.

DISCUSSION

The three anthropometric indices tested were approximately equivalent in their ability to predict diabetes. Sensitivity and specificities differed among ethnic and gender groups.

Abdominal adiposity values associated with established body mass indexes in white, black and hispanic Americans. A study from the Third National Health and Nutrition Examination Survey

PURPOSE

To determine whether white, black and hispanic young (17-39y) and middle-aged (40-59y) adults, and elderly (60-90y) Americans have the same values of abdominal adiposity (estimated from waist circumference (WC) at the established levels of overweight (body mass index, BMI 25-29.9 kg/m2) and obesity (BMI > or = 30 kg/m2).

METHODS

Data (n=16,120) from the US Third National Health and Nutrition Survey were utilized. Age-adjusted linear regression analyses were used to estimate gender- and ethnic-specific WC values corresponding to overweight and obesity. Receiver operating characteristic (ROC) curves were also employed to determine the choices of WC values corresponding to the established BMI cut-off points. With ROC, gender- and ethnic-specific cut-off points producing the best combination of sensitivity and specificity were selected as optimal thresholds for WC values corresponding to the established BMI cut-off points.

RESULTS

WC values associated with the established BMI were lower in blacks and hispanics compared with whites. In men, the WC values that corresponded to overweight ranged from 89 to 106 cm, from 84 to 95 cm, and from 87 to 97 cm in whites, blacks and hispanics, respectively. The corresponding values for obesity ranged from 99 to 110 cm, from 96 to 107 cm, and from 97 to 108 cm. The WC values that corresponded to overweight in women ranged from 82 to 91 cm, from 81 in to 90 cm, and from 83 to 92 cm in whites, blacks and hispanics, respectively. The analogous values for obesity ranged from 94 to 101 cm, from 93 to 100cm, and from 94 to 101 cm.

CONCLUSIONS

The lack of higher WC values in blacks (particularly women) and hispanics at the same levels of BMI for whites challenges previously held assumptions regarding the role of abdominal adiposity in cardiovascular disease experienced by non-whites. Defining the anthropometric variables that satisfactorily describe reasons for ethnic differences in cardiovascular disease is one of the challenges for future research.

Impact of age on associations between weight and mortality

The effect of age on the weight associated with the lowest mortality and the effect of age on the mortality risk associated with obesity are issues fraught with methodologic complexities. Current evidence supports the notion that the body mass index associated with the lowest mortality falls within the range of 18.5 to 24.9 in men and women between the ages of 30 and 74. The impact of age on the mortality risk associated with obesity changes with age, however, and the direction of the trend depends upon the measure used.

Dyslipidemia and abdominal obesity: an assessment in three general populations

Several studies show a relationship between abdominal obesity and cardiovascular diseases, partially mediated through an altered metabolism of dyslipidemia. The present study was aimed at testing the robustness of this association across three contrasted populations and at assessing the performances of abdominal obesity as a screening tool for dyslipidemia. Data were drawn from three population health surveys recently conducted in two regions of a developed country (Switzerland, mostly of Caucasian origin, n = 2650) and in a less developed country (Seychelles, Indian Ocean, mostly of black descent, n = 806). Dyslipidemia was defined as a ratio of total cholesterol to high-density lipoprotein cholesterol (TC-HDL) greater than 5. Two anthropometric circumference measurements, waist-to-hip ratio (WHR) and waist circumference (WC), were used to define abdominal obesity either as WHR >/= 0.9 in men and WHR >/= 0.8 in women or as WC >/= 94 cm and WC >/= 80 cm, respectively. A consistent direct association between abdominal obesity and dyslipidemia (odds ratios varying from 1.85 to 4.56) was found in the three populations, independently of gender, age, body mass index, blood pressure, and smoking. This consistency across ethnicities and environments strengthens the hypothesis of a common etiopathological mechanism. The sensitivity for detecting dyslipidemia was generally higher for abdominal obesity, based on either WHR or WC, than for criteria based on the other risk factors under study. In addition, the sensitivity was higher in the study populations with a low prevalence of dyslipidemia (Swiss women and Seychellois of both sexes) than in the others. These findings support that WHR and WC may be useful as simple and inexpensive screening tools to select individuals eligible for more sophisticated and costly serum lipid determinations, especially in developing countries.

The body mass index-mortality relationship in white and African American women

OBJECTIVE

To examine the association of body mass index to all-cause and cardiovascular disease (CVD) mortality in white and African American women.

RESEARCH METHODS AND PROCEDURES

Women who were members of the American Cancer Society Prevention Study I were examined in 1959 to 1960 and then followed 12 years for vital status. Data for this analysis were from 8,142 black and 100,000 white women. Body mass index (BMI) was calculated from reported height and weight. Associations were examined using Cox proportional hazards modeling with some analyses stratified by smoking (current or never) and educational status (less than complete high school or high school graduate).

RESULTS

There was a significant interaction between ethnicity and BMI for both all-cause (p<0.05) and CVD mortality (p<0.001). BMI (as a continuous variable) was associated with all-cause mortality in white women in all four groups defined by smoking and education. In black women with less than a high school education, there were no significant associations between BMI mortality. For high school-educated black women, there was a significant association between BMI and all-cause mortality. Among never smoking women with at least a high school education, models using the lowest BMI as the reference indicated a 40% higher risk of all-cause mortality at a BMI of 35.9 in black women vs. 27.3 in white women.

DISCUSSION

The impact of BMI on mortality was modified by educational level in black women; however, BMI was a less potent risk factor in black women than in white women in the same category of educational status.

Education, health behaviors, and the black-white difference in waist-to-hip ratio

Few epidemiologic studies have investigated the impact of body mass index, low educational attainment, cigarette smoking, and physical activity on the considerable black-white difference in waist-to-hip ratio. These relationships were assessed with multivariable linear regression among 3,094 adults (24% black) who were examined in 1987 in South Carolina. The unadjusted mean waist-to-hip ratio was lower for black men than for white men (-0.03 units) and higher for black women than for white women (+0.03 units). After adjustment for age, body mass index, education, smoking, and physical activity, the black-white difference in mean waist-to-hip ratio was -0.02 units (p < 0.001) among men and +0.01 units (p < 0.01) among women. Although differing distributions of age, body mass index, and educational attainment accounted for a 59% reduction in the black-white difference among women, these factors did not explain the difference among men. Thus, these results suggest that other environmental or biologic factors may also play an important role in the marked variation in body fat distribution between the two ethnic groups. The results also support the importance of the prevention of cigarette smoking and overweight in potentially preventing abdominal obesity in both black adults and white adults.

Obesity, fat patterning and cardiovascular risk

Investigators have refined the study of the relationship of adiposity to disease by differentiating body shapes on the basis of the physical location of adipose tissue on the body. Different combinations of anthropometric measurements have been investigated as indicators of fat distribution. Recently combinations of easily obtained anthropometric measurements have been studied as correlates of visceral fat as measured by more complex measures such as computed tomography and magnetic resonance imaging. Despite difficulties in the measurement of the regional distribution of adipose tissue, several studies have shown that an upper body, centralized or abdominal fat pattern is correlated with increased CVD risk factors and CVD risk. The majority of studies have been cross-sectional, although several prospective cohort studies have examined relationships between fat distribution and mortality or incidence of morbidity over rather long time intervals. Results from the Charleston Heart Study indicate these relationships may differ by race and gender. More research is needed to define the role of fat patterning and changes in fat patterning on disease. Also, the relationship between total fatness and fat distribution to morbidity and mortality in specific populations and ethnic groups needs further exploration.