Racial effects on body composition: it's not all black and white

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.

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.

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.