Body composition by dual-energy X-ray absorptiometry in black compared with white women

Perceptual body image tasks require ethnically appropriate stimuli

Current body ideals and perceived weight status are often assessed with tests that include images which depict BMI dependent morphological changes in body shape. These images are almost exclusively based on White European (WE) bodies. However, East Asian (EA) and South Asian (SA) people have a different body composition and pattern of adipose deposition for a given BMI. As such, matching someone's body from an EA or SA background to a WE body may lead to errors in estimation, as there are no equivalent bodies to match against. Therefore, we 3D scanned EA, SA and WE female volunteers and constructed computer-generated imagery (CGI) bodies based on a statistical analysis of the size and shape variation specific to each ethnic identity. We then asked participants to make judgements between pairs of bodies of the same or different ethnic identity as themselves. When presented with ethnically different stimuli, EA and SA participants significantly over-estimate body size and WE participants significantly under-estimate. Additionally, ethnically mismatched stimuli lead to significantly greater uncertainty about body size judgements. For the first time, we show that ethnically appropriate stimuli need to be used to assess body judgements and should be developed as a matter of urgency.

Retaining Race in Chronic Kidney Disease Diagnosis and Treatment

The best overall measure of kidney function is glomerular filtration rate (GFR) as commonly estimated from serum creatinine concentrations (eGFRcr) using formulas that correct for the higher average creatinine concentrations in Blacks. After two decades of use, these formulas have come under scrutiny for estimating GFR differently in Blacks and non-Blacks. Discussions of whether to include race (Black vs. non-Black) in the calculation of eGFRcr fail to acknowledge that the original race-based eGFRcr provided the same CKD treatment recommendations for Blacks and non-Blacks based on directly (exogenously) measured GFR. Nevertheless, the National Kidney Foundation and the American Society of Nephrology Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease removed race in CKD treatment guidelines and pushed for the immediate adoption of a race-free eGFRcr formula by physicians and clinical laboratories. This formula is projected to negate CKD in 5.51 million White and other non-Black adults and reclassify CKD to less severe stages in another 4.59 million non-Blacks, in order to expand treatment eligibility to 434,000 Blacks not previously diagnosed and to 584,000 Blacks previously diagnosed with less severe CKD. This review examines: 1) the validity of the arguments for removing the original race correction, and 2) the performance of the proposed replacement formula. Excluding race in the derivation of eGFRcr changed the statistical bias from +3.7 to -3.6 ml/min/1.73m2 in Blacks and from +0.5 to +3.9 in non-Blacks, i.e., promoting CKD diagnosis in Blacks at the cost of restricting diagnosis in non-Blacks. By doing so, the revised eGFRcr greatly exaggerates the purported racial disparity in CKD burden. Claims that the revised formulas identify heretofore undiagnosed CKD in Blacks are not supported when studies that used kidney failure replacement therapy and mortality are interpreted as proxies for baseline CKD. Alternatively, a race-stratified eGFRcr (i.e., separate equations for Blacks and non-Blacks) would provide the least biased eGFRcr for both Blacks and non-Blacks and the best medical treatment for all patients.

Obesity and Race May Explain Differential Burden of White Matter Hyperintensity Load

OBJECTIVE

Compared to European Americans, research indicates that African Americans have higher white matter hyperintensity (WMH) load; however, the clinical and biological bases underlying this higher burden are poorly understood. We hypothesize that obesity may explain differences in WMH between African and European Americans.

METHODS

Participants enrolled in longitudinal brain aging studies (n=292; 61% Female; 92% European American; mean age=69.6±7.7) completed evaluations including medical exams, neuroimaging, and sociodemographic surveys. Overweight/obese status defined as body mass index ≥30 kg/m2, and WMH load, captured by FLAIR images, as sum of deep and periventricular volumes, scored using the Fazekas scale (0-6), WMH≥4 considered high.

RESULTS

Logistic regression analyses, adjusted for age, sex, hypertension, and smoking history, indicated that age and interaction between race and obesity were significant predictors of WMH, demonstrating that obesity significantly moderated the relationship between race and WMH. Age independently increased the odds of high WMH by 16% (OR=1.16, 95% CI=1.09-1.23, p<0.001). Stratified analysis indicates that older European Americans had increased WMH (OR=1.17, 95% CI=1.09-1.23, p<0.001), while obese African Americans had increased WMH (OR=27.65, 95% CI=1.47-519.13, p<0.05). In a case controlled subgroup matched by age, sex, and education (n=48), African Americans had significantly higher WMH load (27% vs 4%, Χ 2=5.3, p=0.02).

CONCLUSION

Results denote that age predicted WMH among European Americans, while obesity predicted WMH among African Americans. Matched sample analyses indicate that obesity increases the odds of WMH, though more pronounced in African Americans. These findings suggest that obesity may explain the differential burden of white matter hyperintensity load, signifying public health and clinical importance.

Does Education Close the Black-White Physical Activity and Obesity Gaps?

Objective: The purpose of the study was to investigate physical activity patterns and body mass index (BMI) among black and white women in college to determine if attending college acts as a catalyst for sustaining physical activity and for closing the black-white physical activity and obesity gaps. Participants/Methods: 111 undergraduate women (black N = 42; white N = 69) aged 18-25 volunteered to wear Fitbit Zip^TM activity trackers for 7 days. Height and weight measurements were used to compute BMI. Results: White women had higher levels of physical activity, lower weight status, and lower BMIs than black women. Conclusions: Racial disparities were evident; however, both groups had low to moderate levels of physical activity. Required physical education programing that targets women in college could lead to sustained physical activity.

Inflammation markers on benign breast biopsy are associated with risk of invasive breast cancer in African American women

PURPOSE

Markers of inflammation, including crown-like structures of the breast (CLS-B) and infiltrating lymphocytes (IL), have been identified in breast tissue and associated with increased risk of breast cancer (BrCa), however most of this work has been performed in primarily non-Hispanic white women. Here, we examined whether CLS-B and IL are associated with invasive BrCa in African American (AA) women.

METHODS

We assessed breast biopsies from three 5-year age-matched groups: BrCa-free AA women (50 Volunteer) from the Komen Normal Tissue Bank (KTB) and AA women with a clinically-indicated biopsy diagnosed with benign breast disease (BBD) from our Detroit cohort who developed BrCa (55 BBD-cancer) or did not develop BrCa (47 BBD only, year of biopsy matched to BBD-cancer). Mean adipocyte diameter and total adipose area were estimated from digital images using the Adiposoft plugin from ImageJ. Associations between CLS-B, IL, and BrCa among KTB and Detroit biopsies were assessed using multivariable multinomial and conditional logistic regression models.

RESULTS

Among all biopsies, Volunteer and BBD only biopsies did not harbor CLS-B or IL at significantly different rates after adjusting for logarithm of adipocyte area, adipocyte diameter, and BMI. Among clinically-indicated BBD biopsies, BBD-cancer biopsies were more likely to exhibit CLS-B (odds ratio (OR) = 3.36, 95% Confidence Interval (CI): 1.33-8.48) or IL (OR = 4.95, 95% CI 1.76-13.9) than BBD only biopsies after adjusting for total adipocyte area, adipocyte diameter, proliferative disease, and BMI.

CONCLUSIONS

CLS-B and IL may serve as histological markers of BrCa risk in benign breast biopsies from AA women.

Hypometabolizers: Characteristics of Obese Patients with Abnormally Low Resting Energy Expenditure

Weight gain or loss is determined by the difference between calorie intake and energy expenditure. The Mifflin metabolic equation most accurately predicts resting energy expenditure (REE) in morbidly obese patients. Hypometabolizers have a measured REE that is much less than predicted and pose the greatest challenge for weight loss induced by restriction of calorie intake. We studied 628 morbidly obese patients (467 female and 161 men, aged 52.5 ± 15.7 years, body mass index [BMI] of 42.6 ± 7.6 m/kg2 [mean ± SD]). REE was measured using the MedGem® device (REEm) and the percentage variance (δREE%) from the Mifflin-predicted expenditure (REEp) was calculated. Patients with δREE% more than 1 standard deviation from the mean were defined as hypometabolizers (REEm greater than 27% below REEp) and hypermetabolizers (REEm less than 13% above REEp), respectively. Hypometabolizers had greater REEp (1900 ± 301 vs 1719 ± 346 calories, P = 0.005) and lower REEm (1244 ± 278 vs 2161 ± 438 calories, P < 0.0001) than hypermetabolizers. Hypometabolizers, when compared with hypermetabolizers, were taller (167.2 ± 8.4 vs 164.0 ± 10.9 cm, P = 0.04), heavier (123.6 ± 22.2 vs 110.2 ± 23.1 kg, P = 0.006), and had increased BMI (44.1 ± 6.5 vs 40.8 ± 6.5 kg/m2, P = 0.04). Other measured anthropometrics were not different between hypo- and hypermetabolizers. Hypometabolizers were less likely to be diabetic (23 vs 43%, P = 0.03) and more likely to be black (25 vs 5%, P = 0.002) than hypermetabolizers. This study defines hypometabolizers as having variance in REEm more than 27 per cent below that predicted by the Mifflin equation. We could not identify any distinguishing phenotypic characteristics of hypometabolizers, suggesting an influence unrelated to body composition.

The Prediction of Body Composition in African Americans From Spine and Hip Dual-Energy Absorptiometry

Body composition, the makeup of the body's fat and lean tissue, is associated with important health outcomes and provides useful clinical information. Although body composition can be measured with total body dual-energy X-ray absorptiometry (DXA), this is rarely performed. As an alternative to total body DXA measurement, methods for estimation of body composition have been developed. These methods use soft tissue measures from spine and hip DXA to predict body composition and include prediction equations previously published by Leslie and proprietary equations within General Electric densitometry software. However, these estimates have not been tested in African Americans (AA), an ethnicity with a different distribution of fat than Caucasians (CA). Therefore, we examined the performance of the existing models in 99 CA and 162 AA subjects over the age of 40 who had total body, spine, and hip DXA measurements. We observed that existing models estimated body composition well in CA but underestimated fat mass and overestimated lean mass in AA. AA subjects were then randomly divided into 2 equal-sized subgroups-the first to develop new prediction equations and the second to independently validate them. We found that body composition can be more accurately estimated using either a new model that we derived in AA subjects using backward stepwise elimination or by adding a fixed offset for AA to the previously published model. Our results demonstrate that body composition estimates from spine and hip DXA require consideration of race/ethnicity.

Obesity, Diabetes, and the Risk of Invasive Group B Streptococcal Disease in Nonpregnant Adults in the United States

Background

Rates of invasive group B Streptococcus (GBS) disease, obesity, and diabetes have increased in US adults. We hypothesized that obesity would be independently associated with an increased risk of invasive GBS disease.

Methods

We identified adults with invasive GBS disease within Active Bacterial Core surveillance during 2010–2012 and used population estimates from the Behavioral Risk Factor Surveillance System to calculate invasive GBS incidence rates. We estimated relative risks (RRs) of invasive GBS using Poisson analysis with offset denominators, with obesity categorized as class I/II (body mass index [BMI] = 30–39.9 kg/m²) and class III (BMI ≥ 40.0 kg/m²).

Results

In multivariable analysis of 4281 cases, the adjusted RRs of invasive GBS disease were increased for obesity (class I/II: RR, 1.52; 95% confidence interval [CI], 1.14–2.02; and class III: RR, 4.87; 95% CI, 3.50–6.77; reference overweight) and diabetes (RR, 6.04; 95% CI, 4.77–7.65). The adjusted RR associated with class III obesity was 3-fold among persons with diabetes (95% CI, 1.38–6.61) and nearly 9-fold among persons without diabetes (95% CI, 6.41–12.46), compared with overweight. The adjusted RRs associated with diabetes varied by age and BMI, with the highest RR in young populations without obesity. Population attributable risks of invasive GBS disease were 27.2% for obesity and 40.1% for diabetes.

Conclusions

Obesity and diabetes were associated with substantially increased risk of infection from invasive GBS. Given the population attributable risks of obesity and diabetes, interventions that reduce the prevalence of these conditions would likely reduce the burden of invasive GBS infection.

Long term trends and racial/ethnic disparities in the prevalence of obesity

Obesity is an epidemic associated with higher rates of hypertension, diabetes, and cardiovascular diseases. However, significant racial disparities in the prevalence of obesity have been reported. To evaluate racial disparities and trends in the prevalence of obesity and obesity-related diseases. A population-based retrospective cohort study utilized data from the 1985 to 2011 California Behavioral Risk Factor Survey. Trends in obesity prevalence were stratified by age, sex, race/ethnicity, and socioeconomic factors. Multivariate logistic regression models evaluated independent predictors of obesity. The prevalence of obesity in significantly increased from 1985 to 2011 (8.6 vs. 22.8%, p < 0.001). This increase was seen among men and women, and among all race/ethnic, age, and socioeconomic groups. Hypertension and diabetes also increased during this time period (hypertension 20.7-35.9%; diabetes 4.2-11.2%). Obesity prevalence was highest in blacks and Hispanics, and lowest in Asians (blacks 33.3%; Hispanics 28.8%; Asians 9.0%; p < 0.001). Obesity prevalence was associated with lower education level, lower income, and unemployment status. After adjustments for age, sex, co morbidities, and surrogates of socioeconomic status, the increased risk of obesity in blacks and Hispanics persisted (blacks OR 1.51; Hispanics OR 1.18), whereas Asians were less likely to be obese (OR 0.37). While the overall prevalence of obesity increased from 1985 to 2011, significant racial/ethnic disparities in obesity have developed, with the highest prevalence seen in blacks and Hispanics, and the lowest seen in Asians.

Diabetes Mellitus Increases Risk of Hepatocellular Carcinoma in Chronic Hepatitis C Virus Patients: A Systematic Review

BACKGROUND

Rising rates of obesity, diabetes mellitus (DM), and nonalcoholic fatty liver disease (NAFLD) among chronic hepatitis C (HCV) patients may contribute to higher hepatocellular carcinoma (HCC) risk.

AIM

To perform a systematic review evaluating the impact of DM, body mass index (BMI), or steatosis on HCC risk among chronic HCV patients.

METHODS

A structured keyword search of PubMed from January 1, 2001, to July 1, 2014, was performed to identify original articles evaluating the association of DM, BMI, or steatosis with HCC among adults with chronic HCV. Studies involving HCV patients co-infected with human immunodeficiency virus, hepatitis B virus, or other chronic liver diseases with the exception of NAFLD were excluded. Quality assessment utilized the Newcastle-Ottawa scale.

RESULTS

Nine studies (seven cohorts, two case-controls) met inclusion criteria for the final analysis. Five of seven studies analyzing DM demonstrated significantly increased HCC risk associated with concurrent DM with effect sizes ranging from HR 1.73 (95 % CI 1.30-2.30) to RR 3.52 (95 % CI 1.29-9.24). One of three studies analyzing BMI demonstrated a significant association with HCC risk (BMI ≥ 30.0 vs. BMI < 23: RR 4.13, 95 % CI 1.38-12.40). Two of the three studies analyzing steatosis demonstrated significantly higher risk of HCC associated with steatosis ranging from RR 2.81 (95 % CI 1.49-4.41) to OR 6.39 (95 % CI 1.04-39.35).

CONCLUSIONS

Concurrent DM is associated with increased HCC risk among chronic HCV patients. BMI and steatosis may also increase HCC risk, but the limitations of the current studies do not allow us to draw strong conclusions.

Non-alcoholic fatty liver disease among sasang constitutional types: a population-based study in Korea

Background

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and is highly prevalent in populations with metabolic conditions such as obesity and type II diabetes. Specific types of Sasang constitution can act as a risk factor for metabolic diseases, but there are no studies addressing the association between the Sasang constitutional types (SCTs) and NAFLD.

Methods

A total of 1184 individuals (508 males, 676 females) that enrolled in the Korean Genome and Epidemiology Study were included in the present study. Classification of SCTs was done with an integrated diagnostic model. NAFLD was diagnosed when the liver attenuation index (LAI) value was <5 Hounsfield units using computed tomography. Relationships between the SCTs and NAFLD were analyzed using multiple logistic regressions.

Results

The average LAI was 13.3 ± 6.0 in the So-eum (SE) type, 12.3 ± 7.0 in the So-yang (SY) type, and 6.5 ± 9.9 in the Tae-eum (TE) type. Prevalence of NAFLD was 4.7 % in the SE type, 14.0 % in the SY type, and 34 % in the TE type. Even after adjusting for possible confounders, the SY and TE types continued to show a 3.90-fold (95 % CI, 1.60-9.51; P = 0.0028) and 3.36-fold (95 % CI, 1.42-7.92; P = 0.0057) increase in chance of having NAFLD, respectively, compared with the SE type. In the additional analysis including only non-obese subjects, the odds ratio of NAFLD was 3.27 (95 % CI, 1.29-8.29; P = 0.0126) in the SY type and 3.53 (95 % CI, 1.30-9.58; P = 0.0134) in the TE type compared with SE type. In the multivariate analysis to determine which parameter had an independent association with NAFLD, higher body mass index, alanine aminotransferase (ALT), triglyceride (TG), and low high-density lipoprotein cholesterol were independently associated with developing NAFLD in the SY type. In contrast, male sex, alcohol consumption, higher ALT, TG, and fasting glucose were risk factors for NAFLD in the TE type.

Conclusions

These results indicated that the SY and TE types are independent risk factors for NAFLD.

Obesity and Pulmonary Function in African Americans

Background

Obesity prevalence in United States (US) adults exceeds 30% with highest prevalence being among blacks. Obesity is known to have significant effects on respiratory function and obese patients commonly report respiratory complaints requiring pulmonary function tests (PFTs). However, there is no large study showing the relationship between body mass index (BMI) and PFTs in healthy African Americans (AA).

Objective

To determine the effect of BMI on PFTs in AA patients who did not have evidence of underlying diseases of the respiratory system.

Methods

We reviewed PFTs of 339 individuals sent for lung function testing who had normal spirometry and lung diffusion capacity for carbon monoxide (DLCO) with wide range of BMI.

Results

Functional residual capacity (FRC) and expiratory reserve volume (ERV) decreased exponentially with increasing BMI, such that morbid obesity resulted in patients breathing near their residual volume (RV). However, the effects on the extremes of lung volumes, at total lung capacity (TLC) and residual volume (RV) were modest. There was a significant linear inverse relationship between BMI and DLCO, but the group means values remained within the normal ranges even for morbidly obese patients.

Conclusions

We showed that BMI has significant effects on lung function in AA adults and the greatest effects were on FRC and ERV, which occurred at BMI values < 30 kg/m2. These physiological effects of weight gain should be considered when interpreting PFTs and their effects on respiratory symptoms even in the absence of disease and may also exaggerate existing lung diseases.

Ethnic-Specific Criteria for Classification of Body Mass Index: A Perspective for Asian Indians and American Diabetes Association Position Statement

Definitions for overweight and obesity are universally applied using body mass index (BMI), based on morbidity and mortality data derived from white populations. However, several studies have shown higher body fat, excess metabolic perturbations, and cardiovascular risk factors at lower value of BMI in Asian versus white populations. Definitive guidelines have been published to classify a BMI of ≥23 kg/m(2) and ≥25 kg/m(2) as overweight and obese, respectively, by the Indian Consensus Group (for Asian Indians residing in India) and a BMI of ≥23 kg/m(2) for screening for diabetes by the National Institute of Health and Care Excellence of the United Kingdom (for migrant south Asians) and, in an encouraging initiative recently (2015), by the American Diabetes Association (for all Asian ethnic groups in the United States). Overall, multiple studies, and now several guidelines, emphasize early intervention with diet and physical activity in Asian ethnic groups for prevention and management of obesity-related noncommunicable diseases. By application of these guidelines, an additional 10-15% of the population in India would be labeled as overweight/obese, and more South Asians/Asians will be diagnosed with diabetes in the United Kingdom and the United States. Additional health resources need to be allocated to deal with increasing numbers of Asians with obesity-related noncommunicable diseases, and research is needed to evolve cost-effective interventions. Finally, consensus based on data is needed so that the World Health Organization and other international agencies could take definitive steps for revision of classification of BMI for Asian populations globally.

Ethnic disparities in the association of body mass index with the risk of hypertension and diabetes

Despite having lower body mass index (BMI) compared to other ethnic groups, Asians continue to develop significant metabolic diseases such as hypertension and diabetes. To evaluate the disparate association of BMI and risk of hypertension and diabetes in Asians. We retrospectively studied 150,753 adults from the 1985-2011 California Behavioral Risk Factor Survey. Trends in prevalence of obesity, hypertension, and diabetes were stratified by ethnicity. Multivariate logistic regression models evaluated the incremental effect of one unit BMI increase on risk of hypertension and diabetes and the disparate risks of hypertension and diabetes at different BMI thresholds. Asians had the lowest BMI among all groups. However, the impact of increasing BMI on risk of hypertension and diabetes was significantly greater in Asians. For each one unit increase in BMI, Asians were significantly more likely to have hypertension (OR 1.15; 95% CI 1.13-1.18) compared to non-Hispanic whites, blacks, and Hispanics. Similar trends were seen for diabetes (Asians: OR 1.15; 95% CI 1.13-1.18). The risk of hypertension in Asians with BMI ≥ 22 was similar to non-Hispanic whites with BMI ≥ 27 and blacks with BMI ≥ 28. The risk of diabetes in Asians with BMI ≥ 28 was similar to non-Hispanic whites with BMI ≥ 30. Despite lower overall BMI compared to other groups, weight gain in Asians is associated with significantly higher risks of hypertension and diabetes. Compared to other ethnic groups, similar risks of hypertension and diabetes are seen in Asians at much lower BMI.

Lifecourse socioeconomic position and 16 year body mass index trajectories: differences by race and sex

OBJECTIVE

The aim of this study is to evaluate the association between lifecourse socioeconomic position (SEP) and changes in body mass index (BMI), and assess disparities in these associations across racial/ethnic groups.

METHODS

With longitudinal data from 4 waves of the Americans' Changing Lives Study (1986-2002), we employed mixed-effects modeling to estimate BMI trajectories for 1174 Blacks and 2323 White adults. We also estimated associations between these trajectories and lifecourse SEP variables, including father's education, perceived childhood SEP, own education, income, wealth, and financial security.

RESULTS

Blacks had higher baseline BMIs, and steeper increases in BMI, compared to Whites. Childhood SEP, as measured by high father's education, was associated with lower baseline BMI among Whites. High education was associated with a lower baseline BMI within both race and sex categories. Income had contrasting effects among men and women. Higher income was associated with higher BMI only among males. Associations between indicators of SEP and BMI trajectories were only found for Whites.

CONCLUSIONS

Our study demonstrates that lifecourse SEP may influence adult BMI differently within different racial and sex groups.

Transition to sarcopenia and determinants of transitions in older adults: a population-based study

BACKGROUND

Diagnostic criteria for sarcopenia from appendicular lean mass (ALM), strength, and performance have been proposed, but little is known regarding the progression of sarcopenia. We examined the time course of sarcopenia and determinants of transitioning toward and away from sarcopenia.

METHODS

ALM, gait speed, and grip strength were assessed seven times over 9 years in 2,928 initially well-functioning adults aged 70-79. Low ALM was defined as less than 7.95 kg/m(2) (men) or less than 6.24 kg/m(2) (women), low performance as gait speed less than 1.0 m/s, low strength as grip strength less than 30 kg (men) or less than 20 kg (women). Presarcopenia was defined as low ALM and sarcopenia as low ALM with low performance or low strength. Hidden Markov modeling was used to characterize states of ALM, strength, and performance and model transitions leading to sarcopenia and death. Determinants of transitioning toward and away from sarcopenia were examined with logistic regression.

RESULTS

Initially, 54% of participants had normal ALM, strength, and performance; 21% had presarcopenia; 5% had sarcopenia; and 20% had intermediate characteristics. Of participants with normal ALM, strength, and performance, 1% transitioned to presarcopenia and none transitioned to sarcopenia. The greatest transition to sarcopenia (7%) was in presarcopenic individuals. Low-functioning and sarcopenia states were more likely to lead to death (12% and 13%). Higher body mass index (p < .001) and pain (p = .05) predicted transition toward sarcopenia, whereas moderate activity predicted transition from presarcopenia to more normal states (p = .02).

CONCLUSIONS

Pain, physical activity, and body mass index, potentially modifiable factors, are determinants of transitions. Promotion of health approaching old age is important as few individuals transition away from their initial state.

Increasing trends in central obesity among Chinese adults with normal body mass index, 1993-2009

Background

Central obesity is thought to be more pathogenic than overall obesity and studies have shown that the association between waist circumference (WC) and mortality was strongest in those with a normal body mass index (BMI). The objective of our study was to determine secular trends in the prevalence of central obesity (WC ≥ 90 cm for men and ≥ 80 cm for women) among Chinese adults with normal BMI from 1993 to 2009 and to examine the impact of performance of combined BMI and WC on the prevalence of obesity in Chinese adults.

Methods

We used data from the China Health and Nutrition Survey (CHNS) conducted from 1993 to 2009. From which we included a total of 52023 participants aged ≥ 18 years.

Results

The age-standardized prevalence of central obesity among Chinese adults with BMI < 25 kg/m² increased from 11.9% in 1993 to 21.1% in 2009 (P for linear trend <0.001). The upward trends were noted in both genders, all ages, rural/urban settings, and education groups (all P for linear trend <0.001), with greater increments in men, participants aged 18–64 years, and rural residents (P for interaction terms survey × sex, survey × age, and survey × rural/urban settings were 0.042, 0.003, and < 0.001, respectively). Trends in the prevalence of central obesity were similar when a more stringent BMI < 23 kg/m² cut point (Asian cut point) was applied. Central obesity is associated with a higher risk of incident hypertension within normal BMI category. More than 65% individuals with obesity would be missed if solely BMI was measured.

Conclusions

We observed an upward trend in the prevalence of central obesity among participants with normal BMI irrespective of sex, age, rural/urban settings, and education level. Central obesity is associated with a higher risk of incident hypertension within normal BMI category. Approximately two thirds of the individuals with obesity would be missed if WC was not measured. It is, therefore, urgent to emphasize the importance of WC as a measure to monitor the prevalence of obesity.

Gestational weight gain as a predictor of longitudinal body mass index transitions among socioeconomically disadvantaged women

BACKGROUND

Socioeconomically disadvantaged women are at greater risk for gestational weight gain and postpartum weight retention compared to socioeconomically advantaged women. This study examines the effect of gestational weight gain on body mass index (BMI) transitions 5 years after pregnancy in socioeconomically disadvantaged women.

METHODS

Gestational weight gain was assessed in 2136 postpartum women participating in the Fragile Families and Child Well-being study who experienced full-term, singleton gestations. Longitudinal BMI transitions were defined as a change or stability in BMI category between two time points: BMI before the index pregnancy and BMI 5 years after the index pregnancy. Logistic regression models estimated the association between gestational weight gain and longitudinal BMI transitions, controlling for health before the index pregnancy, pregnancy history, and sociodemographic characteristics.

RESULTS

Excessive gestational weight gain was related to transitioning to a higher BMI category 5 years after the index pregnancy. Compared to white women, black and Hispanic women were more likely to transition or maintain a higher BMI category. Pregnancy history (i.e., parity at index pregnancy, interim pregnancy) and public assistance participation were associated with transitioning to a higher BMI category.

CONCLUSIONS

Among socioeconomically disadvantaged women, excessive gestational weight gain is related to transitioning to, but not maintaining, a higher weight category 5 years after the index pregnancy. Black and Hispanic women who are also socioeconomically disadvantaged and overweight or obese before conception may benefit from preconception or postpartum counseling about the long-term effect of gaining excessive weight during pregnancy and in the years immediately after childbirth.

Body fat distribution is associated with lumbar spine bone density independently of body weight in postmenopausal women

OBJECTIVE

To assess the association between the body fat distribution and axial bone mineral density (BMD) in postmenopausal women with or without hormone replacement therapy (HRT).

DESIGN

Cross-sectional population-based study.

SETTING

University of Eastern Finland, Bone and Cartilage Research Unit, Kuopio, Finland.

POPULATION

198 postmenopausal women, mean age 67.5 (1.9 SD), mean BMI 27.1 (3.9 SD).

METHODS

Regional body composition and BMD assessed by dual X-ray absorptiometry (DXA, Prodigy).

MAIN OUTCOME MEASURES

Spinal and Femoral BMD.

RESULTS

Out of the body composition parameters, FM was the main determinant of postmenopausal bone mass. Only the lumbar spine (L2-L4) BMD, not the femoral neck BMD, was positively associated with the trunk FM. Positive trends for association were revealed between the spinal BMD and the trunk FM regardless of the use of HRT. Adjustments did not change the results.

CONCLUSIONS

Higher trunk fat mass was associated with the spinal BMD, but not with the hip BMD in postmenopausal women, irrespective of the HRT use. In addition to biological factors, uncertainties related to DXA measurements in patients with varying body mass may contribute to this phenomenon.

Is the 1975 Reference Man still a suitable reference?

BACKGROUND/OBJECTIVE

In 1975, a Reference Man for the estimation of radiation doses without adverse health effects was created. However, during the past few decades, considerable changes in body weight and body composition were observed, as a result of which, new in vivo technologies of body composition analysis are now available. Thus, the Reference Man might be outdated as adequate standard to assess medication and radiation doses. The objective of this study was to compare body composition of an adult population with 1975 Reference Man data, thereby questioning its value as a suitable reference.

METHODS

Body composition was assessed in 208 healthy, Caucasian subjects (105 males, 103 females) aged 18-78 years with a body mass index range of 16.8-35.0 kg/m(2). Fat mass (FM) and muscle mass (MM) were assessed by dual-energy X-ray absorptiometry, organ masses (OMs) were measured by magnetic resonance imaging.

RESULTS

There was a considerable variance in body weight and body composition. When compared with Reference Man, great differences in body composition were found. Men and women of the study population were heavier, taller and had more FM, MM and higher masses of brain, heart and spleen. These differences did not depend on age. Relationships between body weight and body composition were investigated by general linear regression models, whereby deviations in FM, MM and heart mass disappeared, whereas differences in brain and spleen mass persisted.

CONCLUSIONS

Our data indicate the need of a modern Reference Man and thus a recalculation of medical radiation doses and medication.

Anthropometric measures and glucose levels in a large multi-ethnic cohort of individuals at risk of developing type 2 diabetes

AIMS/HYPOTHESES

We determined: (1) which of BMI, waist circumference, hip circumference and WHR has the strongest association and explanatory power for newly diagnosed type 2 diabetes and glucose status; and (2) the impact of considering two measures simultaneously. We also explored variation in anthropometric associations by sex and ethnicity.

METHODS

We performed cross-sectional analysis of 22,293 men and women who were from five ethnic groups and 21 countries, and at risk of developing type 2 diabetes. Standardised anthropometric associations with type 2 diabetes and AUC of glucose status from OGTT (AUC(OGTT)) were determined using multiple regression. Explanatory power was assessed using the c-statistic and adjusted r (2).

RESULTS

An increase in BMI, waist circumference or WHR had similar positive associations with type 2 diabetes, AUC(OGTT) and explanatory power after adjustment for age, sex, smoking and ethnicity (p < 0.01). However, using BMI and WHR together resulted in greater explanatory power than with other models (p < 0.01). Associations were strongest when waist circumference and hip circumference were used together, a combination that had greater explanatory power than other models except for BMI and WHR together (p < 0.01). Results were directionally similar according to sex and ethnicity; however, significant variations in associations were observed among these subgroups.

CONCLUSIONS/INTERPRETATION

The combination of BMI and WHR, or of waist circumference and hip circumference has the best explanatory power for type 2 diabetes and glucose status compared with a single anthropometric measure. Measurement of waist circumference and hip circumference is required to optimally identify people at risk of type 2 diabetes and people with elevated glucose levels.

Estimation of total-body and regional soft tissue composition from DXA bone densitometry of the lumbar spine and hip

The percent fat in soft tissues adjacent to the lumbar spine and proximal femur, which are required parameters in the calculation of bone mineral by conventional dual-energy X-ray absorptiometry (DXA) of the spine and hip, were analyzed for their relationship with the total-body soft tissue-scanning derivatives. The cohort (N=149), consisting of stable actively treated male human immunodeficiency virus HIV-positive patients, was split in half to obtain prediction equations with one half to be validated by the other half. Prediction equations for the dependent variables total-body fat, total-body lean mass, trunk fat, total arm + leg fat, and leg fat were derived by step-down multiple regression. A Bland-Altman comparison of the predicted and observed values showed that the limits of agreement were too large to be clinically helpful. The correlations of the ratio of adjacent spine/hip fat with ratios of trunk/arm + leg fat and trunk/leg fat, markers of peripheral lipoatrophy in HIV, were 0.725 and 0.780, respectively. The 3 ratios were compared with the clinical diagnosis of the presence or absence of peripheral lipoatrophy by receiver operating characteristic analysis. The area under the curve was 0.720 for adjacent spine/hip fat ratio and 0.655 and 0.699 for trunk/arm + leg fat and trunk/leg fat, respectively; they were not significantly different. In conclusion, for male HIV-positive patients, the difference between predicted values and actual values rendered limits of agreement that were too wide to be clinically acceptable. The ratio of percent fat in the lumbar spine region to percent fat in the proximal femur region reflected the presence of peripheral lipoatrophy as effectively as the trunk/peripheral fat ratio that was derived from the total-body scan.

Accuracy of current body mass index obesity classification for white, black, and Hispanic reproductive-age women

OBJECTIVE

To compare the National Institutes of Health's (NIH) body mass index (BMI)-based classification to identify obesity in comparison with the World Health Organization (WHO), which uses percent body fat, among white, black, and Hispanic reproductive-aged women.

METHODS

Body weight, height, BMI, and percent body fat (dual-energy X-ray absorptiometry generated) were determined for 555 healthy adult women aged 20-33 years (mean+/-standard deviation 26.5+/-4.0 years). Diagnostic accuracy of the NIH-based obesity definition (BMI of 30 kg/m or higher) was determined using the WHO criterion standard (percent body fat greater than 35%).

RESULTS

Obesity as defined by the NIH (BMI 30 kg/m or higher) and by WHO (percent body fat greater than 35%) classified 205 (36.9%) and 350 (63.1%) of the women as obese, respectively. The NIH-defined obesity cutoff values had 47.8%, 75.0%, and 53.9% sensitivity in white, black and Hispanic, women, respectively. White and Hispanic women had 2.9% greater percent body fat than black women for a given BMI. Receiver operating characteristics curves analyses showed that the respective sensitivities improved to 85.6%, 81.3%, and 83.2%, and that 311 women (56.0%) were classified as obese as a whole when race or ethnic-specific BMI cutoff values driven by our data (BMI at or above 25.5, 28.7, and 26.2 kg/m for white, black, and Hispanic women, respectively) were used to detect percent body fat-defined obesity.

CONCLUSION

Current BMI cutoff values recommended by the NIH failed to identify nearly half of reproductive-aged women who met the criteria for obesity by percent body fat. Using race or ethnic-specific BMI cutoff values would more accurately identify obesity in this population than the existing classification system.

Racial differences in body fat distribution among reproductive-aged women

We examined the influence of race/ethnicity on body fat distribution for a given body mass index (BMI) among reproductive-aged women. Body weight, height, and body fat distribution were measured with a digital scale, wall-mounted stadiometer, and dual-energy x-ray absorptiometry, respectively, on 708 healthy black, white, and Hispanic women 16 to 33 years of age. Multiple linear regression was used to model the relationship between race/ethnicity and different body fat distribution variables after adjusting for BMI, age at menarche, and demographic and lifestyle variables. For a given BMI, white women had the highest total fat mass (FM(total)), trunk fat mass (FM(trunk)), and leg fat mass (FM(leg)), whereas Hispanic women had the highest percentage of FM(trunk) (%FM(trunk)) and trunk-to-limb fat mass ratio (FMR(trunk-to-limb)). Conversely, black women had the lowest FM(total), FM(trunk), percentage body fat mass (%FM), %FM(trunk), and FMR(trunk-to-limb), and the highest percentage of FM(leg). The %FM was similar in whites and Hispanics and lower in blacks. The race x BMI interactions were significant for almost all of the body fat distribution variables. Increasing in differences with increasing BMI were apparent between blacks and whites in FM(trunk), %FM(trunk), FMR(trunk-to-limb), %FM(leg), and %FM, and between blacks and Hispanics in FM(trunk), %FM(trunk), FMR(trunk-to-limb), and FM(leg). In summary, the distribution of body fat for a given BMI differs by race among reproductive-aged women. These findings raise questions regarding universally applied BMI-based guidelines for obesity and have implications for patient education regarding individual risk factors for cardiovascular disease and metabolic complications.

Comparisons of percentage body fat, body mass index, waist circumference, and waist-stature ratio in adults

BACKGROUND

Body mass index (BMI), waist circumference (WC), and the waist-stature ratio (WSR) are considered to be possible proxies for adiposity.

OBJECTIVE

The objective was to investigate the relations between BMI, WC, WSR, and percentage body fat (measured by dual-energy X-ray absorptiometry) in adults in a large nationally representative US population sample from the National Health and Nutrition Examination Survey (NHANES).

DESIGN

BMI, WC, and WSR were compared with percentage body fat in a sample of 12,901 adults.

RESULTS

WC, WSR, and BMI were significantly more correlated with each other than with percentage body fat (P < 0.0001 for all sex-age groups). Percentage body fat tended to be significantly more correlated with WC than with BMI in men but significantly more correlated with BMI than with WC in women (P < 0.0001 except in the oldest age group). WSR tended to be slightly more correlated with percentage body fat than was WC. Percentile values of BMI, WC, and WSR are shown that correspond to percentiles of percentage body fat increments of 5 percentage points. More than 90% of the sample could be categorized to within one category of percentage body fat by each measure.

CONCLUSIONS

BMI, WC, and WSR perform similarly as indicators of body fatness and are more closely related to each other than with percentage body fat. These variables may be an inaccurate measure of percentage body fat for an individual, but they correspond fairly well overall with percentage body fat within sex-age groups and distinguish categories of percentage body fat.

Human organ/tissue growth algorithms that include obese individuals and black/white population organ weight similarities from autopsy data

Physiologically based pharmacokinetic (PBPK) models need the correct organ/tissue weights to match various total body weights in order to be applied to children and the obese individual. Baseline data from Reference Man for the growth of human organs (adrenals, brain, heart, kidneys, liver, lungs, pancreas, spleen, thymus, and thyroid) were augmented with autopsy data to extend the describing polynomials to include the morbidly obese individual (up to 250 kg). Additional literature data similarly extends the growth curves for blood volume, muscle, skin, and adipose tissue. Collectively these polynomials were used to calculate blood/organ/tissue weights for males and females from birth to 250 kg, which can be directly used to help parameterize PBPK models. In contrast to other black/white anthropomorphic measurements, the data demonstrated no observable or statistical difference in weights for any organ/tissue between individuals identified as black or white in the autopsy reports.

Ethnic differences in adiposity and body composition: the First Nations bone health study

The purpose of this study was to compare patterns of adiposity and soft tissue composition in First Nations and white Canadian women. A population-based cross-sectional study was performed. A random age-stratified sample of 206 urban First Nations women and 177 white women was recruited. Soft tissue composition was analyzed with dual-energy X-ray absorptiometry. Analysis of covariance (ANCOVA) models were used to assess ethnicity in models that adjusted for body mass, body mass index (BMI), and socio-demographic factors. Obesity (BMI>or=30.0 kg/m2) was more common in First Nations women (48.1%) than in white women (36.2%, Fisher's exact test p=0.012). Mean trunk fat tissue mass fraction and total body fat mass fraction (as a percent of soft tissue) were greater in First Nations women than in white women (p<0.0001). Trunk lean tissue was also greater in First Nations women (p=0.027), but total body lean tissue was similar. The mean trunk adiposity index was strongly related to ethnicity (First Nations +0.5%+/-2.5% versus white -1.7%+/-2.6%, p<0.0001). Preferential fat accumulation in the trunk of First Nations women persisted after adjustment for body mass, BMI, and other socio-demographic variables (p<0.0001). First Nations women differ from white women in terms of fat and lean tissue mass and distribution. First Nations women had a preferential increase in trunk fat and this may contribute to high reported rates of diabetes, metabolic syndrome, and cardiovascular events.

Genetic markers for ancestry are correlated with body composition traits in older African Americans

Individual-specific percent European ancestry was assessed in 1,277 African Americans. We found significant correlations between proportion of European ancestry and several musculoskeletal traits, indicating that admixture mapping may be a useful strategy for locating genes affecting these traits.

INTRODUCTION

Genotype data for admixed populations can be used to detect chromosomal regions influencing disease risk if allele frequencies at disease-related loci differ between parental populations. We assessed evidence for differentially distributed alleles affecting bone and body composition traits in African Americans.

METHODS

Bone mineral density (BMD) and body composition data were collected for 1,277 African and 1,790 European Americans (aged 70-79). Maximum likelihood methods were used to estimate individual-specific percent European ancestry for African Americans genotyped at 37 ancestry-informative genetic markers. Partial correlations between body composition traits and percent European ancestry were calculated while simultaneously adjusting for the effects of covariates.

RESULTS

Percent European ancestry (median = 18.7%) in African Americans was correlated with femoral neck BMD in women (r = -0.18, p < 10(-5)) and trabecular spine BMD in both sexes (r = -0.18, p < 10(-5)) independently of body size, fat, lean mass, and other covariates. Significant associations of European ancestry with appendicular lean mass (r = -0.19, p < 10(-10)), total lean mass (r = -0.12, p < 10(-4)), and total body fat (r = 0.09, p < 0.002) were also observed for both sexes.

CONCLUSIONS

These results indicate that some population differences in body composition may be due to population-specific allele frequencies, suggesting the utility of admixture mapping for identifying susceptibility genes for osteoporosis, sarcopenia, and obesity.

Is the current BMI obesity classification appropriate for black and white postmenopausal women?

OBJECTIVE

To evaluate the relation between body fatness (%Fat) and body mass index (BMI) and to evaluate the validity of the BMI standards for obesity established by the NIH in older black and white postmenopausal women.

RESEARCH METHODS

Height, weight, BMI, and %Fat, assessed by DXA, were determined for 296 healthy, independently living women ranging in age from 50 to 80 years (M+/-s.d.; 64.4+/-7.8 years).

RESULTS

Per NIH guidelines, 32% were classified as obese (> or = 30 kg/m2, mean BMI = 28.1+/-5.5 kg/m2). In contrast, using the %Fat criterion of 38% advocated by Lohman to define obesity, 47% of our sample was obese (mean %Fat=37.3+/-6.2%). A moderately high curvilinear relation existed between BMI and %Fat (R = 0.82, SEE = 3.57 %Fat, P<0.05). Race added meaningfully to the prediction of %Fat (P<0.05) such that for the same BMI, black women will have 1% lower body fatness than white women. Based on a %Fat > or = 38 as the criterion for obesity, receiver operating characteristic (ROC) analysis, performed separately by race, indicated that the currently accepted BMI cutpoint for obesity produced low sensitivity (69% and 61% for black and white women, respectively). Alternatively, BMI values > or = 28.4 kg/m2 for black women and > or = 26.9 kg/m2 for white women to define obesity maximized classification accuracy.

CONCLUSION

We conclude that current BMI categories may not be appropriate for identifying obesity among postmenopausal women. Furthermore, the relation between BMI and %Fat is different in black compared to white women but remains constant from the sixth through the eighth decade of life.

Ultrasound of the calcaneus and bone mineral density differs in older black and white women but is not impacted by current physical activity

Black women have lower fracture rates, primarily due to bone-dependent factors; however, the racial differences in quantitative ultrasound (QUS) for older black and white women are poorly characterized, especially in regard to the mediating effects of physical activity. The primary aim of this study was to determine if QUS measures differ in age- and body-size-matched older black and white women and to explore if the racial differences were mediated by differences in current habitual physical activity. We performed dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) measures and QUS measures [broadband ultrasound attenuation (BUA), speed of sound (SOS), quantitative ultrasound index (QUI)] of the calcaneus in 30 black and 30 white women matched in age (68.3 years) and body mass index (30.0 kg/m2). Black women had greater QUS measures of SOS (1,563.6+/-31.7 vs 1,541.2+/-23.4, p=0.003) and QUI (102.6+/-18.5 vs 90.4+/-15.4, p=0.008), with a strong trend for greater BUA (79.2+/-15.1 vs 71.9+/-15.1 m/sec, p=0.066) compared with white women. As expected, black women had greater BMD measures at all sites; whole body (6.8%, p<0.010), lumbar spine (10.4%, p=0.008), proximal femur (14.2%; p<0.001) and femoral neck (20.3%; p<0.001), compared with white women. Although white women reported expending 45% more energy (p=0.03) in moderate intensity physical activity than black women on a weekly basis, current physical activity did not attenuate the difference in QUS measures between the races. The relations between QUS and BMD measures were similar in black compared with white women. After controlling for BMD, the racial differences in QUS measures were not apparent, precluding the conclusion that bone quality independently contributes to the reduction in fracture risk in older black women. The impact of current physical activity on QUS measures in older black and white women is negligible.

Comparison between 60 matched pairs of postmenopausal black and white women: Analysis of risk factors related to bone mineral density

PURPOSE

Osteoporosis is a systemic disease in which bone density is reduced, leading to weakness of the skeleton and increased vulnerability to fractures. The purpose of this study was to compare known or suspected risk factors (medical, gynecological, and lifestyle characteristics) related to bone loss between 60 matched pairs of black and white postmenopausal women.

METHODS

The two racial groups were matched one for one on selective anthropometric variables [age (years), standing height (cm), and body weight (kg)] in order to equate age and body size between groups. Information on risk factors was obtained from an orally administered questionnaire and body composition variables (in addition to those used for matching) assessed by anthropometry and total body dual energy X-ray absorptiometry (DXA). Four skinfold sites (chest, triceps, mid-axillary, and abdomen) were measured with Harpendon calipers and four body circumferences (chest, forearm contracted, waist, and gluteal) were assessed with a Gulick tape. DXA radius, spine, femur, and whole body measurements were obtained on a Hologic QDR-2000 with software version 7.20.

RESULTS

White women reported significantly higher proportions of alcohol use, family history of broken bones, and a greater utilization of hormones, calcium and vitamins than did black women. Black women reported a greater numbers who had other diseases (i.e., overactive thyroid, diabetes, rheumatoid arthritis, or kidney stones). Although age and body weight were similar in both groups, black women had greater lean tissue and less body fat than white women. Blacks had significantly higher bone mineral density across all body sites with the exception of the mid- and ultra-distal radius.

CONCLUSION

On the basis of these data, it was concluded that part of the difference often observed in bone density between black and white postmenopausal women might be due to lifestyle factors.

Breast cancer and obesity: an update

Obesity has a complicated relationship to both breast cancer risk and the clinical behavior of the established disease. In postmenopausal women, particularly the elderly, various measures of obesity have been positively associated with risk. However, before menopause increased body weight is inversely related to breast cancer risk. In both premenopausal and postmenopausal breast cancer, the mechanisms by which body weight and obesity affect risk have been related to estrogenic activity. Obesity has also been related to advanced disease at diagnosis and with a poor prognosis in both premenopausal and postmenopausal breast cancer. Breast cancer in African-American women, considering its relationship to obesity, exhibits some important differences from those described in white women, although the high prevalence of obesity in African-American women may contribute to the relatively poor prognosis compared with white American women. Despite the emphasis on estrogens to explain the effects of obesity on breast cancer, other factors may prove to be equally or more important, particularly as they relate to expression of an aggressive tumor phenotype. Among these, this review serves to stress insulin, insulin-like growth factor-I, and leptin, and their relationship to angiogenesis, and transcriptional factors.

Total body protein: a new cellular level mass and distribution prediction model

BACKGROUND

Protein is an important body component, and the presently accepted criterion method for estimating total body protein (TBPro) mass--in vivo neutron activation (IVNA) analysis--is unavailable to most investigators and is associated with moderate radiation exposure.

OBJECTIVE

The objective was to derive a theoretical cellular level TBPro mass and distribution model formulated on measured total body potassium, total body water, and bone mineral and to evaluate the new model with the IVNA method as the criterion.

DESIGN

The new model was developed on the basis of a combination of theoretical equations and empirically derived coefficients. TBPro mass estimates with the new model were evaluated in healthy women (n = 183) and men (n = 24) and in men with AIDS (n = 84). Total body nitrogen was measured by IVNA, total body potassium by whole-body (40)K counting, total body water by tritium dilution, and bone mineral by dual-energy X-ray absorptiometry.

RESULTS

The group mean (+/- SD) TBPro mass estimates in healthy women and men and men with AIDS (8.2 +/- 0.9, 11.0 +/- 1.8, and 10.5 +/- 1.1 kg, respectively) with the new model were similar to IVNA criterion estimates (8.9 +/- 0.9, 11.1 +/- 1.6, and 10.9 +/- 1.2 kg, respectively). TBPro mass estimates with the new model correlated highly with the IVNA estimates in all subjects combined (r = 0.92, P < 0.001). The new model suggests that the composite TBPro mass within each group consists mainly of cellular protein (75-79%) and, to a lesser extent, protein in extracellular solids (19-23%) and extracellular fluid (approximately 2%).

CONCLUSION

The new model provides a non-IVNA approach for estimating protein mass and distribution in vivo.

Influence of distribution of lean body mass on resting metabolic rate after weight loss and weight regain: comparison of responses in white and black women

BACKGROUND

Little is known about the effect of weight change on regional lean body mass (LBM) distribution or on racial differences in resting metabolic rate (RMR).

OBJECTIVE

The study compared total and regional LBM patterns in white and black women after weight loss and regain and assessed the influence of regional LBM on variances in RMR.

DESIGN

Eighteen white and 22 black women who did not differ in age, weight, and height were studied 3 times: in the overweight state, after weight reduction to the normal-weight state, and after 1 y without intervention. Total and regional lean and fat masses were assessed by dual-energy X-ray absorptiometry.

RESULTS

White and black women did not differ significantly in mean (+/- SD) weight loss (13.4 +/- 3.6 and 12.7 +/- 3.2 kg, respectively) and regain (6.1 +/- 5.5 and 6.4 +/- 5.4 kg, respectively). Black subjects had significantly less trunk LBM and significantly more limb LBM at each time point (P < 0.05). In both races, weight regain was associated with significant increases in limb LBM (P < 0.05) but not in trunk LBM (P = 0.21). RMR, adjusted for total LBM and fat mass, was significantly higher in white women after weight loss (P < 0.01) and regain (P < 0.01). However, no racial difference was found when RMR was adjusted for LBM distribution.

CONCLUSIONS

In both races, trunk LBM decreased with weight loss and remained lower, despite significant weight regain, which potentially reflected decreased organ mass. Regional LBM distribution explained the racial difference in RMR.

One- and two-year change in body composition as measured by DXA in a population-based cohort of older men and women

Changing body composition has been suggested as a pathway to explain age-related functional decline. No data are available on the expected changes in body composition as measured by dual-energy X-ray absorptiometry (DXA) in a population-based cohort of older persons. Body composition data at baseline, 1-yr follow-up, and 2-yr follow-up was measured by DXA in 2,040 well-functioning black and white men and women aged 70-79 yr, participants of the Health, Aging, and Body Composition Study. After 2 yr, a small decline in total body mass was observed (men: -0.3%, women: -0.4%). Among men, fat-free mass and appendicular lean soft tissue mass (ALST) decreased by -1.1 and -0.8%, respectively, which was masked by a simultaneous increase in total fat mass (+2.0%). Among women, a decline in fat-free mass was observed after 2 yr only (-0.6%) with no change in ALST and body fat mass. After 2 yr, the decline in ALST was greater in blacks than whites. Change in total body mass was associated with change in ALST (r = +0.58 to +0.70; P < 0.0001). Among participants who lost total body mass, men lost relatively more ALST than women, and blacks lost relatively more ALST than whites. In conclusion, the mean change in body composition after a 1- to 2-yr follow-up was 1-2% with a high interindividual variability. Loss of ALST was greater in men compared with women, and greater in blacks compared with whites, suggesting that men and blacks may be more prone to muscle loss.

A longitudinal study of bone density in midlife women

A longitudinal study of 386 healthy Black and White women aged 35-60 years was conducted to determine the effects of physical activity and other related factors on lumbar bone mineral density over 24 months. Bone mineral density of the lumbar spine, L2-L4, was measured using dual energy x-ray (Hologic 1000). Physical activity levels in three dimensions (leisure, household, and occupational) from both a lifelong and current perspective were obtained by questionnaire. Body mass index was calculated from measured weight in kilograms divided by measured height in meters squared. Calcium, caffeine, and alcohol intake was estimated using a food frequency questionnaire. Age, race, and smoking were determined by self-report. Radioimmunoassays of follicle stimulating hormone (FSH) and estradiol were used to validate self-reports of menopausal status. Multiple regression analysis revealed that race, age, weight, FSH, calcium, and years of tobacco intake formed the best model at baseline (r(2) = 0.32) and at 24 months (r(2) = 0.303). Physical activity was not a significant predictor for bone mineral density at either time point. There were cross-sectional changes of bone mineral density with race, age, and menopausal status. Black women had significantly higher bone mineral density than White women. However, an age-related decline in bone mineral density was exhibited in both Black and White women. Perimenopausal women had significantly lower bone mineral density as compared with premenopausal women. Furthermore 37 (9.6%) women at baseline and 34 (11%) at 24 months were designated at risk for fracture.

Assessing the validity of body mass index standards in early postmenopausal women

OBJECTIVE

To examine the relationship between percentage of total body fat (%Fat) and body mass index (BMI) in early postmenopausal women and to evaluate the validity of the BMI standards for obesity established by the NIH.

RESEARCH METHODS AND PROCEDURES

Three hundred seventeen healthy, sedentary, postmenopausal women (ages, 40 to 66 years; BMI, 18 to 35 kg/m(2); 3 to 10 years postmenopausal) participated in the study. Height, weight, BMI, and %Fat, as assessed by DXA, were measured. Receiver operating characteristic analysis was performed to evaluate the ability of BMI to discriminate obesity from non-obesity using 38%Fat as the criterion value.

RESULTS

A moderately high relationship was observed between BMI and %Fat (r = 0.81; y = 1.41x + 2.65) with a SE of estimate of 3.9%. Eighty-one percent of other studies examined fell within 1 SE of estimate as derived from our study. Receiver operating characteristic analysis showed that BMI is a good diagnostic test for obesity. The cutoff for BMI corresponding to the criterion value of 38%Fat that maximized the sum of the sensitivity and specificity was 24.9 kg/m(2). The true-positive (sensitivity) and false-positive (1--specificity) rates were 84.4% and 14.6%, respectively. The area under the curve estimate for BMI was 0.914.

DISCUSSION

There is a strong association between %Fat and BMI in postmenopausal women. Current NIH BMI-based classifications for obesity may be misleading based on currently proposed %Fat standards. BMI >25 kg/m(2) rather than BMI >30 kg/m(2) may be superior for diagnosing obesity in postmenopausal women.

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.

Body composition in human infants at birth and postnatally

The predictive values of anthropometric measurements, race, gender, gestational and postnatal ages, and season at birth and at study for the total body dual energy X-ray absorptiometry (DXA)-derived lean mass (LM), fat mass (FM) and fat mass as a percentage of body weight (%FM) were determined in 214 singleton appropriate birth weight for gestational age infants [101 Caucasian (60 boys, 41 girls) and 113 African American (55 boys, 58 girls)]. Gestational ages were 27-42 wk and the infants were studied between birth and 391 d, weighing between 851 and 13446 g. In addition, predictive value of body weight, LM and FM for DXA bone measurements was also determined. Scan acquisition used Hologic QDR 1000/W densitometer and infant platform and scans without significant movement artifacts were analyzed using software 5.64p. Body weight, length, gender and postnatal age were significant predictors of LM (adjusted R:(2) >0. 94) and FM (adjusted R:(2) >0.85). Physiologic variables had little predictive value for %FM except in the newborns (adjusted R:(2) 0. 69). Body weight was the dominant predictor of LM and FM, although length had similar predictive value for LM with increasing postnatal age. Female infants had less LM and more FM throughout infancy (P: < 0.01). LM or FM offered no advantage over body weight in the prediction of bone mass measurements. DXA is a useful means with which to determine body composition, and our data are important in the design and assessment of nutritional intervention studies.