Comparison of body composition in black and white premenopausal women

Biological Differences between Late 19th and Early 20th Century Urban and Rural Residence

Communities urbanize when the net benefits to urbanization exceed rural areas. Body mass, height, and weight are biological welfare measures that reflect the net difference between calories consumed and calories required for work and to withstand the physical environment. Individuals of African-decent had greater BMIs, heavier weights, and shorter statures. Urban farmers had lower BMIs, shorter statures, and lower weight than rural farmers. Over the late 19th and early 20th centuries, urban and rural BMIs, height, and weight were constant, and rural farmers had greater BMIs, taller statures, and heavier weights than urban farmers and workers in other occupations.

Weight and economic development: current net nutrition in the late 19th- and early 20th-century United States

When traditional measures for material and economic welfare are scarce or unreliable, height and the body mass index (BMI) are now widely accepted measures that represent cumulative and current net nutrition in development studies. However, as the ratio of weight to height, BMI does not fully isolate the effects of current net nutrition. After controlling for height as a measure for current net nutrition, this study uses the weight of a sample of international men in US prisons. Throughout the late 19th- and early-20th centuries, individuals with darker complexions had greater weights than individuals with fairer complexions. Mexican and Asian populations in the US had lower weights and reached shorter statures. Black and white weights stagnated throughout the late 19th- and early-20th centuries. Agricultural workers' had greater weights than workers in other occupations.

Late 19th, early 20th century US, foreign-born body mass index values in the United States

Little work exists that compares the BMIs of 19^th century foreign-born and US-born natives. Russian, Italian, German, and French BMIs were 5.1, 3.9, 2.9, and 1.8 percent higher than that of North Americans; Asians were nearly 4.2 percent lower. African-Americans and multiracial/multiethnic individual BMIs were 4.9 and 3.8 percent greater than fairer complexioned whites, indicating there was no multiracial/multiethnic BMI advantage. Farm laborers and ranchers had BMIs that were 2.9 percent and 2.2 percent greater, respectively, than that of workers with no occupations.

Physical Performance and Vitamin D in Elderly Black Women-The PODA Randomized Clinical Trial

CONTEXT

There is limited information on the influence of vitamin D on physical performance in black Americans.

OBJECTIVE

To determine if maintenance of serum 25(OH)D >75 nmol/L prevents a decline in physical performance.

DESIGN

The Physical Performance, Osteoporosis and Vitamin D in African American Women (PODA) trial had a prospective, randomized, placebo controlled, double-dummy design with two arms: one of which is placebo vitamin D3 adjusted to maintain serum 25(OH)D >75 nmol/L.

PATIENTS

The target population was healthy elderly black women with serum 25(OH)D between 20 and 65 nmol/L. The trial was 3 years in duration with measurement of physical performance every 6 months: grip strength, Short Physical Performance Battery (SPPB), 10 chair rises, and 6-minute walk distance. A total of 260 women entered the study and 184 completed 3 years. Mean age was 68.2 years. Baseline 25(OH)D was 53 nmol/L; total SPPB was 11 (10 to 12).

SETTING

Research center in an academic health center.

MAIN OUTCOMES MEASURE

Prevention of decline in physical performance measures.

INTERVENTION

Participants were randomly assigned to placebo or active vitamin D. Vitamin D3 dose was adjusted to maintain serum 25(OH)D >75 nmol/L.

RESULTS

There was a decline with time in grip strength and the 6-minute walk test. The SPBB increased with time. There were no substantial differences between the placebo and active vitamin D3 groups with respect to the temporal patterns observed for any of the performance measures.

CONCLUSION

There is no benefit of maintaining serum 25(OH)D >75 nmol/L in preventing the decline in physical performance in healthy black American women.

Inter-population variation of histomorphometric variables used in the estimation of age-at-death

Population variation of several microscopic structures used in age-at-death estimation was assessed for three different population samples. The aim of the study was to determine if the need exists for population-specific standards when dealing with individuals of African and European origin. A total sample 223 bone sections from the anterior cortex of the femur (n = 99 black South Africans, n = 94 white South Africans and n = 30 Danish individuals) were analysed using a stereological protocol. Variables assessed included the average number of osteons per grid area (OPD), osteon size and Haversian canal size. ANCOVA was employed for assessment of statistically significant differences. The results indicated that OPD differed significantly between the three groups, but that osteon size was similar for all individuals. Haversian canal size showed unpredictable changes with age and high levels of variation, making it unsuitable to use for age estimation as a single factor. As there are conflicting opinions in the literature on whether to use population-specific equations for the estimation of age-at-death or not, this paper provided additional insight into the use of specific variables and its related variation between groups.

Net nutrition on the late 19th and early 20th century American Great Plains: a robust biological response to the challenges to the Turner Hypothesis

In 1893, Frederick Jackson Turner proposed that America’s Western frontier was an economic ‘safety-valve’ – a place where settlers could migrate when conditions in eastern states and Europe crystallized against their upward economic mobility. However, recent studies suggest the Western frontier’s material conditions may not have been as advantageous as Jackson proposed because settlers lacked the knowledge and human capital to succeed on the Plains and Far Western frontier. Using stature, BMI and weight from five late 19th and early 20th century prisons, this study uses 61,276 observations for men between ages 15 and 79 to illustrate that current and cumulative net nutrition on the Great Plains did not deteriorate during the late 19th and early 20th centuries, indicating that recent challenges to the Turner Hypothesis are not well supported by net nutrition studies.

The vitamin D metabolite ratio (VMR) as a predictor of functional biomarkers of bone health

CONTEXT

The vitamin D metabolite ratio (VMR) (serum 24,25(OH)₂ D₃ /25(OH)D₃ ) has been proposed as a biomarker of vitamin D sufficiency to replace serum 25(OH)D.

OBJECTIVE

To examine the relationships of 24,25(OH)₂ D₃ and VMR to functional biomarkers of bone health following vitamin D supplementation.

SETTING

An ambulatory research centre.

DESIGN

Serum from a previous research study of dose response of PTH, calcium absorption and bone turnover to vitamin D supplementation was analysed for vitamin D metabolites (25(OH)D, 24,25(OH)₂ D₃ ).

OUTCOME

The relationship of serum 24,25(OH)₂ D₃ and VMR to calcium absorption, PTH and bone turnover markers was examined.

RESULTS

Although there were strong correlations of serum 25(OH)D with 24,25(OH)₂ D₃ and free 25(OH)D, its correlation with VMR was lower. After vitamin D supplementation, the change in 25(OH)D, 24,25(OH)₂ D₃ and VMR was associated with the change in calcium absorption, PTH and CTX. The correlation of the change in PTH with the change in metabolites was the lowest for VMR. Moreover, estimated dose response for standardized values of vitamin D metabolites showed a beta-coefficient for VMR that was significantly less in magnitude compared to other metabolites.

CONCLUSION

Serum 24,25(OH)₂ D₃ is closely associated with the dose response of serum 25(OH)D to vitamin D supplementation. However, the VMR does not appear to be equivalent to either of these metabolites in its response to increasing vitamin D intake or its association with PTH. It is unlikely that VMR will replace 25(OH)D as a biomarker for vitamin D sufficiency.

Urinary calcium excretion in postmenopausal African American women

Aim: The objective of this study was to develop a reference range for urine calcium excretion (both 24-hour and fasting) for African American women compared to White women. In addition, the variables that determine urine calcium excretion were identified. Material: Data were analyzed for baseline studies of healthy postmenopausal volunteers who participated in seven separate studies conducted at one site. Methods: Some studies included fasting urine Ca/Cr and others 24-hour urine calcium excretion. 24-hour urine calcium was considered with and without correction for urinary creatinine excretion. Calcium was measured initially by atomic absorption spectrophotometry and more recently by an automated method (ADVIA 2400 Chemistry System). Results: Participants were considered healthy based on history and physical and routine laboratory studies. Those screened who had a history of nephrolithiasis were excluded. A reference range for 24-hour urine calcium and fasting urine calcium/creatinine was developed. Reference intervals of 11 – 197 mg/24-hour urine calcium excretion and of 0.007 – 0.222 of fasting Ca/Cr were found for African American women compared to 21 – 221 mg/24 hours and 0.019 – 0.264 in White women, respectively. Urine creatinine excretion was higher in African Americans consistent with their higher muscle mass. Conclusion: Urine calcium excretion is lower in postmenopausal African American than White women. The reference range developed should be considered in the diagnosis of hypocalciuric states and may also be useful in the diagnosis of hypercalciuria.

Body-Weight Change and Physical Functioning Among Young Old Adults

Objectives: The main purpose of this study is to examine if body weight change is a potential risk factor for the onset of functional impairment across time among various functional domains. Methods: Using longitudinal data from the Health and Retirement Study, logistic regression models on the onset of functional impairment over three time points are estimated for young old adults. Results: Results indicate that weight gain is associated with greater risk of lower body mobility impairment. An increase in body mass index of greater than 5% increases the likelihood of the onset of lower body mobility functional impairment. Discussion: Study findings support the promotion of healthy weight management. Future studies in this area may want to investigate effective interventions that contribute to healthy weight maintenance among this cohort.

Trabecular bone score (TBS) in postmenopausal African American women

Trabecular bone score (TBS) is a newly developed parameter that can be derived from DXA scans of the spine and may reflect bone quality. This study provides TBS values in healthy postmenopausal women of African descent.

INTRODUCTION

African American women have a lower risk for osteoporotic fractures as a result of higher bone density and better bone quality. We examined TBS in postmenopausal African American women since there are no previous reports in this population.

METHODS

This was a study of healthy African American volunteers using baseline values prior to their participation in two vitamin D intervention studies conducted at an ambulatory research center of an academic health center.

RESULTS

The study population consisted of 518 healthy postmenopausal African American women with a mean age of 66 years and a BMI of 30.1. Mean TBS (L1 to L4) was 1.300(.100 SD). Significant negative correlations were found between TBS and age and BMI. None of the biochemical variables were significantly correlated with TBS whereas the various bone density sites were correlated with TBS.

CONCLUSION

TBS values for African American women are higher than those reported in the literature for white women and are inversely related to age and BMI.

The relationship between 19th century BMIs and family size: Economies of scale and positive externalities

The use of body mass index values (BMI) to measure living standards is now a well-accepted method in economics. Nevertheless, a neglected area in historical studies is the relationship between 19th century BMI and family size, and this relationship is documented here to be positive. Material inequality and BMI are the subject of considerable debate, and there was a positive relationship between BMI and wealth and an inverse relationship with inequality. After controlling for family size and wealth, BMI values were related with occupations, and farmers and laborers had greater BMI values than workers in other occupations.

Fibroblast growth factor 23, vitamin D, and health disparities among African Americans with chronic kidney disease

Compared with Caucasians, African Americans have lower circulating concentrations of 25-hydroxyvitamin D (25(OH)D), the major storage form of vitamin D, leading to the widespread assumption that African Americans are at higher risk of vitamin D deficiency. However, the finding that African Americans maintain better indices of musculoskeletal health than Caucasians throughout their lifespan despite having lower circulating 25(OH)D concentrations suggests that the relationship between vitamin D deficiency and racial health disparities may not be so straightforward. The fairly recent emergence of fibroblast growth factor 23 (FGF23) may help resolve some of this uncertainty. FGF23 strongly modulates both systemic and local activation of 25(OH)D, playing a potentially important role in the degree to which lower 25(OH)D concentrations impact health outcomes, including differences in the incidence and rate of progression of chronic kidney disease by race. This review critically assesses ongoing controversies surrounding the relationship between vitamin D and racial disparities in chronic kidney disease outcomes, and how FGF23 may help to clarify the picture.

Black and white body mass index values in developing nineteenth century Nebraska

Little is known about late 19th and early 20th century BMIs on the US Central Plains. Using data from the Nebraska state prison, this study demonstrates that the BMIs of dark complexioned blacks were greater than for fairer complexioned mulattos and whites. Although modern BMIs have increased, late 19th and early 20th century BMIs in Nebraska were in normal ranges; neither underweight nor obese individuals were common. Farmer BMIs were consistently greater than those of non-farmers, and farm labourer BMIs were greater than those of common labourers. The BMIs of individuals born in Plains states were greater than for other nativities, indicating that rural lifestyles were associated with better net current biological living conditions.

Racial and ethnic differences in obesity and overweight as predictors of the onset of functional impairment

OBJECTIVES

To examine racial and ethnic differences in the effects of body mass index (BMI) on the onset of functional impairment over 10 years of follow-up.

DESIGN

Longitudinal analyses of a cohort from a nationally representative survey of community-dwelling American adults.

SETTING

Six waves (1996-2006) of the Health and Retirement Study (HRS).

PARTICIPANTS

Two groups of HRS participants aged 50 and older without functional impairment at baseline (1996): 5,884 with no mobility difficulty and 8,484 with no activity of daily living (ADL) difficulty.

MEASUREMENTS

Mobility difficulty was a composite measure of difficulty walking several blocks, walking one block, climbing several flights of stairs, and climbing one flight of stairs. ADL difficulty was measured as difficulty in dressing, bathing or showering, eating, and getting in and out of bed without help. The association between baseline BMI and risk of developing functional impairment was estimated using generalized estimating equation models.

RESULTS

Overweight and obesity were significant predictors of functional impairment. Overweight and obese Hispanics were 41% and 91% more likely, respectively, to develop ADL disability than whites in the same BMI categories. Overweight and severely obese blacks were also more likely than their white counterparts to develop ADL disability. Risk of developing ADL difficulty was higher for Hispanics than for blacks in the obese category. No significant differences in onset of mobility difficulty were found between racial or ethnic groups within any BMI category.

CONCLUSION

Blacks and Hispanics were at higher risk than whites of ADL but not mobility impairment. In addition to weight control, prevention efforts should promote exercise to reduce functional impairment, especially for blacks and Hispanics, who are at higher risk.

Sunlight and other determinants of circulating 25-hydroxyvitamin D levels in black and white participants in a nationwide U.S. study

Circulating 25-hydroxyvitamin D (25(OH)D), a marker for vitamin D status, is associated with bone health and possibly cancers and other diseases; yet, the determinants of 25(OH)D status, particularly ultraviolet radiation (UVR) exposure, are poorly understood. Determinants of 25(OH)D were analyzed in a subcohort of 1,500 participants of the US Radiologic Technologists (USRT) Study that included whites (n = 842), blacks (n = 646), and people of other races/ethnicities (n = 12). Participants were recruited monthly (2008-2009) across age, sex, race, and ambient UVR level groups. Questionnaires addressing UVR and other exposures were generally completed within 9 days of blood collection. The relation between potential determinants and 25(OH)D levels was examined through regression analysis in a random two-thirds sample and validated in the remaining one third. In the regression model for the full study population, age, race, body mass index, some seasons, hours outdoors being physically active, and vitamin D supplement use were associated with 25(OH)D levels. In whites, generally, the same factors were explanatory. In blacks, only age and vitamin D supplement use predicted 25(OH)D concentrations. In the full population, determinants accounted for 25% of circulating 25(OH)D variability, with similar correlations for subgroups. Despite detailed data on UVR and other factors near the time of blood collection, the ability to explain 25(OH)D was modest.

Recent insights into racial differences in bone and mineral metabolism

PURPOSE OF REVIEW

This study reviews recent insights into racial differences in bone from 2010 to 2011.

RECENT FINDINGS

Recent studies have focused on expanding our current understanding of responsible mechanisms for racial differences in osteoporotic fracture risk. Using newer, three-dimensional imaging techniques, these studies demonstrated that racial differences in bone mass and structure are apparent early in adolescence, even when accounting for differences in bone size and muscle mass by race. In addition, recent studies using genetic admixture analysis showed that greater percentage of African admixture was independently associated with higher bone mass and more favorable parameters of bone strength in children and adults. Furthermore, recent studies showed that the relationships between 25-hydoxyvitamin D and bone outcomes differed by race, with lower 25-hydroxyvitamin D levels being associated with lower bone quality and higher fracture risk in whites but not blacks.

SUMMARY

Racial differences in bone mass and strength are apparent early in life, are independently associated with genetic ancestry, and may be partly explained by differences in the relationships between vitamin D and bone metabolism. Further studies are needed to explore these findings, with the ultimate goal of better defining molecular and cellular mechanisms underlying racial differences in bone quality.

Racial differences in the relationship between vitamin D, bone mineral density, and parathyroid hormone in the National Health and Nutrition Examination Survey

It is unclear whether optimal levels of 25-hydroxyvitamin D (25(OH)D) in whites are the same as in minorities. In adult participants of NHANES, the relationships between 25(OH)D, bone mineral density (BMD), and parathyroid hormone (PTH) differed in blacks as compared to whites and Mexican-Americans, suggesting that optimal 25(OH)D levels for bone and mineral metabolism may differ by race.

INTRODUCTION

Blacks and Hispanics have lower 25-hydroxyvitamin D concentrations than whites. However, it is unclear whether 25(OH)D levels considered "optimal" for bone and mineral metabolism in whites are the same as those in minority populations.

METHODS

We examined the relationships between 25(OH)D and parathyroid hormone in 8,415 adult participants (25% black and 24% Mexican-American) in the National Health and Nutrition Examination Surveys 2003-2004 and 2005-2006; and between 25(OH)D and bone mineral density in 4,206 adult participants (24% black and 24% Mexican-American) in the 2003-2004 sample.

RESULTS

Blacks and Mexican-Americans had significantly lower 25(OH)D and higher PTH concentrations than whites (P < 0.01 for both). BMD significantly decreased (P < 0.01) as serum 25(OH)D and calcium intake declined among whites and Mexican-Americans, but not among blacks (P = 0.2). The impact of vitamin D deficiency (25(OH)D ≤ 20 ng/ml) on PTH levels was modified by race/ethnicity (P for interaction, 0.001). Whereas inverse relationships between 25(OH)D and PTH were observed above and below a 25(OH)D level of 20 ng/ml in whites and Mexican-Americans, an inverse association between 25(OH)D and PTH was only observed below this threshold in blacks, with the slope of the relationship being essentially flat (P = 0.7) above this cut-point, suggesting that PTH may be maximally suppressed at lower 25(OH)D levels in blacks than in whites or Mexican-Americans.

CONCLUSIONS

The relationships between 25(OH)D, BMD, and PTH may differ by race among US adults. Whether race-specific ranges of optimal vitamin D are needed to appropriately evaluate the adequacy of vitamin D stores in minorities requires further study.

Myostatin and follistatin polymorphisms interact with muscle phenotypes and ethnicity

PURPOSE

We examined associations among myostatin (MSTN) 2379 A > G and 163 G > A and follistatin (FST) -5003 A > T and -833 G > T single nucleotide polymorphisms (SNP) on the muscle size and the strength response to resistance training (RT).

METHODS

Subjects (n = 645, age = 24.1 +/- 0.2 yr, body mass index [BMI] = 24.2 +/- 0.2 kg x m(-2)) self-disclosed themselves as Caucasian (78.9%), African American (3.6%), Asian (8.4%), Hispanic (5.0%), or Other (4.2%). They were genotyped for MSTN 2379 A > G (n = 645), MSTN 163 G > A (n = 639), FST -5003 A > T (n = 580), and FST -833 G > T (n = 603). We assessed dynamic (one repetition maximum [1RM]) and isometric (maximum voluntary contraction [MVC]) muscle strength and size (cross-sectional area [CSA]) of the elbow flexors before and after 12 wk of unilateral upper-arm RT. Repeated-measures ANCOVA tested associations among genetic variants and muscle phenotypes with age and BMI as covariates.

RESULTS

Baseline MVC was greater among African Americans who were carriers of the MSTN G(2379) allele (AG/GG, n = 15) than the A2379A homozygotes (n = 8; 64.2 +/- 6.8 vs 49.8 +/- 8.7 kg). African Americans who were carriers of the FST T(-5003) allele (n = 12) had greater baseline 1RM (11.9 +/- 0.7 vs 8.8 +/- 0.5 kg) and CSA (24.4 +/- 1.3 vs 19.1 +/- 1.2 cm(2)) than African Americans with the A-5003A genotype (n = 14; P < 0.05). No MSTN or FST genotype and muscle phenotype associations were found among the other ethnic groups (P >or= 0.05).

CONCLUSION

MSTN 2379 A > G and FST -5003 A > T were associated with baseline muscle strength and size among African Americans only. These ethnic-specific associations are hypothesis generating and should be confirmed in a larger sample of African Americans.

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.

African Americans, 25-hydroxyvitamin D, and osteoporosis: a paradox

African Americans have lower serum 25-hydroxyvitamin D concentrations and a lower risk of fragility fractures than do other populations. I review the evidence on factors other than vitamin D that might explain this paradox and the calcium economy in different life stages. Researchers are actively trying to explain this genetically programmed advantage. Factors that could protect African Americans against fracture include their higher peak bone mass, increased obesity rates, greater muscle mass, lower bone turnover rates, and advantageous femur geometry. In addition, bone histomorphometry in young adults shows longer periods of bone formation. Although African Americans fall as frequently as do whites, the direction of their falls and their manner of breaking falls could protect them from fractures. African American girls accrue more calcium than do white girls during adolescence as the result of increased calcium absorption and superior renal calcium conservation. In adulthood, higher parathyroid hormone concentrations do not result in increased bone loss in African Americans because of their skeletal resistance to parathyroid hormone, and their superior renal conservation of calcium persists. These advantages diminish in the elderly, in whom further increases in parathyroid hormone result in increased bone turnover and bone loss. Ultimately, I explain the paradox by multiple factors associated with fracture risk and calcium economy in African Americans. Despite African Americans' reduced risk of osteoporotic fractures, such fractures remain an important public health problem for this population that vitamin D intervention studies have not addressed.

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.

Diabetes is associated independently of body composition with BMD and bone volume in older white and black men and women: The Health, Aging, and Body Composition Study

The association between type 2 diabetes, BMD, and bone volume was examined to determine the effect of lean and fat mass and fasting insulin in the Health, Aging, and Body Composition Study, which included white and black well-functioning men and women 70-79 years of age (N = 2979). Diabetes predicted higher hip, whole body, and volumetric spine BMD, and lower spine bone volume, independent of body composition and fasting insulin.

INTRODUCTION

The purpose of this study was to determine if the association between type 2 diabetes and higher BMD observed in older white women is seen in elderly white men and blacks and to evaluate if higher BMD in diabetic individuals is accounted for by lean mass, fat mass, or fasting insulin differences.

MATERIALS AND METHODS

In the Health, Aging, and Body Composition Study, which included white and black well-functioning men and women 70-79 years of age (N = 2979), 19% of participants had diabetes at baseline. Of those with diabetes, 57% were men, and 62% were black. Multivariate linear regression models examined independent effects of diabetes, lean mass, fat mass, visceral fat, and fasting insulin on BMD and bone volume while adjusting for relevant covariates.

RESULTS AND CONCLUSIONS

Fasting insulin, visceral fat, and volumetric spine BMD, assessed by CT, and lean mass, fat mass, and total hip and whole body BMD, assessed by DXA, were higher (p < or = 0.05 for all) for those with diabetes. Hip BMD was higher in white men (0.99 +/- 0.14 versus 0.93 +/- 0.14 g/cm2, p < 0.001), black men (1.06 +/- 0.17 versus 1.00 +/- 0.15 g/cm2, p < 0.001), white women (0.83 +/- 0.13 versus 0.76 +/- 0.13 g/cm2, p < 0.001), and black women (0.90 +/- 0.15 versus 0.85 +/- 0.15 g/cm2, p < 0.001) with diabetes compared with those without diabetes, although the relationship was attenuated by body composition. In multiple regression models, diabetes was an independent predictor of higher hip, whole body, and volumetric spine BMD in all participants (p < or = 0.001), but lower spine volume (p = 0.01) and higher hip BMD for each race-gender group (p < or = 0.01). Type 2 diabetes was associated with a 4-5% higher total hip BMD in all race-gender groups of elderly adults, independent of body composition and fasting insulin levels.

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.

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.

Hypovitaminosis D prevalence and determinants among African American and white women of reproductive age: third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

Recent reports of rickets among African American children drew attention to the vitamin D status of these infants and their mothers. African American women are at higher risk of vitamin D deficiency than are white women, but few studies have examined determinants of hypovitaminosis D in this population.

OBJECTIVE

We examined the prevalence and determinants of hypovitaminosis D among African American and white women of reproductive age.

DESIGN

We examined 1546 African American women and 1426 white women aged 15-49 y who were not pregnant and who participated in the third National Health and Nutrition Examination Survey (1988-1994). Hypovitaminosis D was defined as a serum 25-hydroxyvitamin D concentration < or =37.5 nmol/L. Multiple logistic regression was used to examine the independent association of dietary, demographic, and behavioral determinants of hypovitaminosis D.

RESULTS

The prevalence of hypovitaminosis D was 42.4 +/- 3.1% ( +/- SE) among African Americans and 4.2 +/- 0.7% among whites. Among African Americans, hypovitaminosis D was independently associated with consumption of milk or breakfast cereal <3 times/wk, no use of vitamin D supplements, season, urban residence, low body mass index, and no use of oral contraceptives. Even among 243 African Americans who consumed the adequate intake of vitamin D from supplements (200 IU/d), 28.2 +/- 2.7% had hypovitaminosis D.

CONCLUSIONS

The high prevalence of hypovitaminosis D among African American women warrants further examination of vitamin D recommendations for these women. The determinants of hypovitaminosis D among women should be considered when these women are advised on dietary intake and supplement use.

Relation of bone mineral density and content to mineral content and density of the fat-free mass

Differences in the mineral fraction of the fat-free mass (M(FFM)) and in the density of the FFM (D(FFM)) are often inferred from measures of bone mineral content (BMC) or bone mineral density (BMD). We studied the relation of BMC and BMD to the M(FFM) and D(FFM) in a heterogeneous sample of 216 young men (n = 115) and women (n = 101), which included whites (n = 155) and blacks (n = 61) and collegiate athletes ( n = 132) and nonathletes (n = 84). Whole body BMC and BMD were determined by dual-energy X-ray absorptiometry (DXA; Hologic QDR-1000W, enhanced whole body analysis software, version 5.71). FFM was estimated using a four-component model from measures of body density by hydrostatic weighing, body water by deuterium dilution, and bone mineral by DXA. There was no significant relation of BMD to M(FFM) (r = 0.01) or D(FFM) (r = -0.06) or of BMC to M(FFM) (r = -0.11) and a significant, weak negative relation of BMC to D(FFM) (r = -0.14, P = 0.04) in all subjects. Significant low to moderate relationships of BMD or BMC to M(FFM) or D(FFM) were found within some gender-race-athletic status subgroups or when the effects of gender, race, and athletic status were held constant using multiple regression, but BMD and BMC explained only 10-17% of the variance in M(FFM) and 0-2% of the variance in D(FFM) in addition to that explained by the demographic variables. We conclude that there is not a significant positive relation of BMD and BMC to M(FFM) or D(FFM) in young adults and that BMC and BMD should not be used to infer differences in M(FFM) or D(FFM).

A Comparison between Composition and Density of the Fat-Free Mass of Young Adult Singaporean Chinese and Dutch Caucasians

BACKGROUND

The body composition was measured in 30 female Singapore Chinese and 34 female Dutch Caucasians aged (mean +/- SD) 22.7 +/- 3.6 years and in 39 male Singapore Chinese and 39 male Dutch Caucasians aged 23.3 +/- 3.2 years.

METHODS

The body fat percentage (BF%) was measured using densitometry and deuterium oxide dilution as well as a chemical four-compartment model, including fat mass, water, mineral, and protein. The chemical composition of the fat-free mass (FFM) and its density were calculated.

RESULTS

Mean body mass index (kg/m(2)) and BF% based on the four-compartment model in the four subgroups were 20.3 +/- 1.5 and 29.7 +/- 5.3 for the Singapore Chinese females, 22.1 +/- 1.2 and 28.9 +/- 5.2 for the Dutch females, 21.5 +/- 2.5 and 19.4 +/- 6.1 for the Singapore males, and 22.2 +/- 1.8 and 15.8 +/- 4.9 for the Dutch males. The contributions to the FFM of water, protein, and mineral were, respectively, 72.8 +/- 1.5, 19.2 +/- 1.8, and 7.9 +/- 0.8% for the Singaporean females and 74.2 +/- 1.4, 18.3 +/- 1.5, and 7.6 +/- 0.5% for the Dutch females. In males these figures were 73.2 +/- 1.7, 19.6 +/- 1.7, and 7.3 +/- 0.5% for the Singaporeans and 72.9 +/- 1.4, 20.5 +/- 1.4, and 6.6 +/- 0.5% for the Dutch. In females, these figures were for all components significantly different between the ethnic groups; in males the differences were significant for protein and mineral only. The calculated densities (kg/l) of the FFM were 1.1074 +/- 0.0057, 1.1012 +/- 0.0051, 1.1027 +/- 0.0065, and 1.1004 +/- 0.0055 for the Chinese females, Caucasian females, Chinese males, and Caucasian males, respectively.

CONCLUSIONS

Although it cannot be excluded that the differences in density and composition of the FFM are due to methodological differences between the study sites, the findings may have consequences for the validity of single (reference) methods due to violation of normally used assumptions. The findings explain the observed underestimation of BF% from density using Siri's formula in the Chinese subjects, especially in females. The use of deuterium oxide as a single method to determine the BF% resulted in a smaller bias than densitometry (overall 1.6 +/- 2.0% for densitometry, 0.3 +/- 1.7% for deuterium dilution), suggesting that the deuterium oxide method may be more suitable as a single method in comparative body composition studies.

Polymorphic variation in the human myostatin (GDF-8) gene and association with strength measures in the Women's Health and Aging Study II cohort

OBJECTIVES

To determine whether polymorphic variation in the myostatin gene differentially influences the maintenance of muscle strength in older adults, and to find supportive evidence in a cohort of older women.

DESIGN

Correlation study of polymorphic variation in a cohort of older women.

SETTING

Representatively sampled older female population living in the eastern half of Baltimore, Maryland.

PARTICIPANTS

Participants were 286 women, age 70 to 79. Of these, 81.1% were Caucasian, 18.8% were African American, and 0.2% were Asian or Hispanic.

MEASUREMENTS

Overall strength was measured with a dynamometer and defined as the sum of the strongest measures of hip, knee, and grip strength on the dominant side.

RESULTS

We identified or confirmed six myostatin polymorphic variants in the Women's Health and Aging Study II population. Of the polymorphisms, K153R is the most common, with an allele frequency of 0.19 in African Americans. Unadjusted mean strength by genotype suggested lower muscle strength in those African-American women with the R genotype compared with those with the K genotype (K/K: 72.50 +/- 13.9 kg (n = 39) vs K/R: 67.14 +/- 11.4 kg (n = 13) vs R/R: 63.1 +/- 11.3 kg (n = 3)). After adjustment for race in a linear regression model, the R genotype remained associated with lower strength levels (P = .04). Statistical significance decreased when body mass index and race were both added to the model (P = .09).

CONCLUSIONS

Recognizing that small sample size in the study of genes of modest effect are unlikely to yield significant differences, these data suggest an association of the R153 allele with lower strength in high-functioning older women, which should be studied further in a larger cohort.

Body fat measurement among Singaporean Chinese, Malays and Indians: a comparative study using a four-compartment model and different two-compartment models

This cross-sectional study compared body fat percentage (BF%) obtained from a four-compartment (4C) model with BF% from hydrometry (using 2H2O), dual-energy X-ray absorptiometry (DXA) and densitometry among the three main ethnic groups (Chinese, Malays and Indians) in Singapore, and determined the suitability of two-compartment (2C) models as surrogate methods for assessing BF% among different ethnic groups. A total of 291 subjects (108 Chinese, seventy-six Malays, 107 Indians) were selected to ensure an adequate representation of age range (18-75 years) and BMI range (16-40 kg/m2) of the general adult population, with almost equal numbers from each gender group. Body weight was measured, together with body height, total body water by 2H2O dilution, densitometry with Bodpod and bone mineral content with Hologic QDR-4500. BF% measurements with a 4C model for the subgroups were: Chinese females 33.5 (sd 7.5), Chinese males 24.4 (sd 6.1), Malay females 37.8 (sd 6.3), Malay males 26.0 (sd 7.6), Indian females 38.2 (sd 7.0), Indian males 28.1 (sd 5.5). Differences between BF% measured by the 4C and 2C models (hydrometry, DXA and densitometry) were found, with underestimation of BF% in all the ethnic-gender groups by DXA of 2.1-4.2 BF% and by densitometry of 0.5-3.2 BF%). On a group level, the differences in BF% between the 4C model and 2H2O were the lowest (0.0-1.4 BF% in the different groups), while differences between the 4C model and DXA were the highest. Differences between the 4C model and 2H2O and between the 4C model and DXA were positively correlated with the 4C model, water fraction (f(water)) of fat-free mass (FFM) and the mineral fraction (f(mineral)) of FFM, and negatively correlated with density of the FFM (D(FFM)), while the difference between 4C model and densitometry correlated with these variables negatively and positively respectively (i.e. the correlations were opposite). The largest contributors to the observed differences were f(water) and D(FFM). When validated against the reference 4C model, 2C models were found to be unsuitable for accurate measurements of BF% at the individual level, owing to the high errors and violation of assumptions of constant hydration of FFM and D(FFM) among the ethnic groups. On a group level, the best 2C model for measuring BF% among Singaporeans was found to be 2H2O.

Differences in skeletal and muscle mass with aging in black and white women

Previous cross-sectional studies using delayed gamma neutron activation analysis and whole body counting suggested that the relationship of total body calcium (TBCa) to total body potassium (TBK) (muscle mass, body cell mass) remained constant with age. This led to the hypothesis that the muscle mass and skeletal mass compartments are integrated in their response to aging. It had also been hypothesized that loss of skeletal and muscle mass was similar between races. In the current study, delayed gamma neutron activation analysis and whole body counting were performed on 90 black and 143 white women 20-69 yr of age. Black women had higher TBCa and TBK values than white women, even when the data were adjusted for age, height, and weight. TBCa was correlated with height and TBK with weight. The estimated decline of skeletal mass (TBCa) from 20 to 70 yr was 18% in black women and 19% in white women. However, the lifetime decline of TBK was only 8% for black women, compared with 22% for white women. Black women may lose TBK more slowly than TBCa with aging, compared with white women. In particular, correlation of TBCa and age was similar for blacks and whites (r = -0.44 and r = -0.54, respectively). However, for TBK these correlations were r = -0.14 and r = -0.42. These data confirm a higher musculoskeletal mass in black women and suggest that the loss of muscle mass with age may be lower in black than in white women. These ethnic differences do not support the hypothesis of an integrated musculoskeletal system, so that these two components should be considered separately. A prospective study is needed to confirm these findings.

Muscle strength and body mass index as long-term predictors of mortality in initially healthy men

BACKGROUND

Muscle weakness, low body weight, and chronic diseases are often observed in the same people; however, the association of muscle strength with mortality, independent of disease status and body weight, has not been elucidated. The aim was to assess hand grip strength as a predictor of all-cause mortality within different levels of body mass index (BMI) in initially disease-free men.

METHODS

Mortality was followed prospectively over 30 years. Maximal hand grip strength tests and BMI assessments were done at baseline in 1965 to 1970. The participants were 6040 healthy men aged 45 to 68 years at baseline living on Oahu, Hawaii.

RESULTS

The death rates per 1000 person years were 24.6 in those with BMI <20, 18.5 in the middle BMI category, and 18.0 in those with BMI > or = 25. For grip strength tertiles, the mortality rates were 24.8 in the lowest, 18.5 in the middle, and 14.0 in the highest third. In Cox regression models, within each tertile of grip strength, BMI showed only minimal effect on mortality. In contrast, in each category of BMI there was a gradient of decreasing mortality risk with increasing grip strength. Among those with BMI <20, the adjusted relative risks (RRs) of mortality over 30 years were 1.36 (95% confidence interval 1.14-1.63) for those in the lowest third of strength at baseline, 1.27 (1.02-1.58) in the middle, and 0.92 (0.66-1.29) in the highest third. Correspondingly, for those with BMI 20-24.99, the RRs of death were 1.25 (1.08-1.45), 1.14 (1.00-1.32), and 1.0 (reference) in the lowest, middle, and highest third of grip strength, respectively. In those with BMI > or =25, the RRs were 1.39 (1.16-1.65) in the lowest, 1.27 (1.08-1.49) in the middle, and 1.14 (0.98-1.32) in the highest third of grip strength. Models were adjusted for age, education, occupation, smoking, physical activity, and body height.

CONCLUSIONS

In healthy middle-aged men, long-term mortality risk was associated with grip strength at baseline, independent of BMI. The possible interpretation of the finding is that early life influences on muscle strength may have long-term implications for mortality. Additionally, higher strength itself may provide greater physiologic and functional reserve that protects against mortality.

Frequent sequence variation in the human myostatin (GDF8) gene as a marker for analysis of muscle-related phenotypes

Myostatin is a recently identified member of the transforming growth factor-beta family of regulatory factors, also known as growth and differentiation factor 8 (GDF8). The nucleotide sequence of human myostatin was determined in 40 individuals. The invariant promoter contains a consensus MyoD binding site, and the coding sequence contains five missense substitutions in conserved amino acid residues (A55T, K153R, E164K, P198A, and I225T). Two of these, A55T in exon 1 and K153R in exon 2, are polymorphic in the general population with significantly different allele frequencies in Caucasians and African Americans (P < 0.001). Neither of the common polymorphisms had a significant impact on muscle mass response to strength training in either Caucasians or African Americans, although skewed allele frequencies preclude detection of small effects. These allelic variants provide markers for examining association between the myostatin gene and interindividual variation in muscle mass and differences in loss of muscle mass with aging.

Energy metabolism in African Americans: potential risk factors for obesity

BACKGROUND

Recent reports have identified a lower resting metabolic rate in African Americans than in whites, but most studies included only females and used short-term measurements with ventilated-hood systems.

OBJECTIVE

Our objective was to compare 24-h measurements of energy metabolism between African American and white women and men using a respiratory chamber.

DESIGN

Thirty-eight African American (x +/- SD: 32 +/- 7 y of age, 24 +/- 10% body fat) and 288 white (31 +/- 7 y of age, 26 +/- 12% body fat) subjects spent 24 h in a respiratory chamber for measurement of 24-h energy expenditure (24EE), sleeping metabolic rate (SMR), 24-h respiratory quotient (24RQ), and substrate oxidation rates.

RESULTS

After adjustment for sex, age, and body composition (by hydrodensitometry), African Americans had lower SMR (-301 +/- 105 kJ/d; P < 0.01) and higher 24RQ (0.014 +/- 0.004; P < 0.001) than whites, whereas 24EE was similar. A sex-specific analysis, using a subset of 38 whites with an equal sex distribution and similar age and body weight, revealed that African American women had lower SMR (-442 +/- 182 kJ/d; P < 0.05) and lower 24EE (-580 +/- 232 kJ/d; P < 0.05), but similar 24RQ values compared with white women. African American men tended to have lower SMRs than white men (-355 +/- 188 kJ/d; P = 0. 07), but had higher 24RQ values, accounting for a 992 +/- 327-kJ/d lower 24-h fat oxidation rate (P < 0.005).

CONCLUSIONS

These data not only confirm the findings of a lower metabolic rate in African American than in white women, but also suggest that fat oxidation is lower in African American men than in white men.

Relation between body fat and age in 4 ethnic groups

BACKGROUND

Previous studies of the relation between age and body fat reached differing conclusions concerning the question of whether body fat is lower in the elderly than in middle-aged persons.

OBJECTIVE

The objectives of this study were to characterize the relation between age and body fat in 4 ethnic groups and test the hypothesis that body fat is lower in the elderly than in middle-aged persons.

DESIGN

Body fat was measured in a sample of 1324 volunteers aged 20-94 y by using a 4-component model of body composition. Four ethnic groups were studied: Asians, blacks, Puerto Ricans, and whites. Regression models were developed for fat mass and fat percentage as functions of age.

RESULTS

In all but one of the groups, a highly significant curvilinear relation between age and body fat was found, indicating a peak amount of body fat in late middle age and lower amounts of body fat at younger and older ages (P < 0.001). The age at which maximum body fat was predicted in the various groups ranged from 53 to 61 y for fat mass and from 55 to 71 y for fat percentage. In Puerto Rican men there was no significant relation between age and fat mass, and the relation between age and fat percentage was linear and positively correlated.

CONCLUSIONS

This study provided data on the relation between age and body fat in 4 ethnic groups and supported the hypothesis that body fat is lower in the elderly than in middle-aged persons.

Relationship of body water compartments to age, race, and fat-free mass

Water compartments were studied in 72 black and 128 white women, aged 20 to 70 years. Total body water (TBW) was measured by tritiated water dilution, and extracellular water (ECW) was measured by using delayed gamma neutron activation for the determination of total body chloride. Intracellular water (ICW) was assessed as the difference between TBW and ECW. Fat-free mass (FFM) was estimated by the measurement of total body potassium (TBK) and total body fat (TBF) by measurement of total body carbon (TBC). Total body protein was calculated from total body nitrogen (TBN). TBW was found to decline with age and to also be significantly influenced by body size. The extracellular water space was 41.5% of TBW. The decline of TBW with age is due primarily to a decline in ICW. The hydration of the FFM increased with age for the overall population because of a decline in TBK and TBN and an increase in ECW. Body composition models that have assumed constancy of hydration should be adjusted not only for gender but for age and body size.

Aging in women--the four-compartment model of body composition

The four-compartment model of body composition was examined in 155 white women through measurement of total body carbon (TBC), nitrogen (TBN), calcium (TBCa), and water levels. The age (mean +/- SD) of the population was 51.4 +/- 13.5 years, and values for the four compartments were as follows (in kilograms): protein 8.9 +/- 1.0, water 30.9 +/- 3.5, mineral 2.6 +/- 0.4, and fat 22.6 +/- 7.3. There was a linear change with age for protein and water, whereas mineral and fat were curvilinear. These latter two compartments also showed differences in premenopausal and postmenopausal rates of change. Various models were fit to the data to adjust for body size and age. Each of the four compartments (mineral, water, fat, and protein) changed with age, with fat increasing and the other compartments declining. The equation, y = age + age2 + height + weight, fit the data as well as the other models. Equations are provided to assess body composition in populations with disorders of nutrition, as well as other illnesses, using height, weight, and age as covariates. Since this was a cross-sectional study, longitudinal studies will have to be performed to confirm the accuracy of rates of change with age predicted with each compartment.