Black or ethnic bbw

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Black or ethnic bbw

Learn More. Body mass index BMI is now the most widely used measure of adiposity on a global scale. Nevertheless, intense discussion centers on the appropriateness of BMI as a phenotypic marker of adiposity across populations differing in race and ethnicity.

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Accordingly, we systematically review the magnitude of these race-ethnic differences across non-Hispanic NH white, NH black and Mexican American adults, their anatomic body composition basis and potential biologically linked mechanisms, using both earlier publications and new analyses from the US National Health and Nutrition Examination Survey.

Our collective observations provide a new framework for critically evaluating the quantitative relations between BMI and adiposity across groups differing in race and ethnicity; reveal new insights into BMI as a measure of adiposity across the adult age-span; identify knowledge gaps that can form the basis of future research and create a quantitative foundation for developing BMI-related public health recommendations.

By providing a quick estimate of adiposity, body mass index BMI is now universally considered a marker of wellness and disease risk 1 — 3. However, many reports now describe race and ethnic differences in BMI—adiposity relationships 4 — 7. The variability in BMI—adiposity associations has led to intense debate on appropriate body weight guidelines for use within specific populations 58 — Why would BMI—adiposity relations Black or ethnic bbw across race and ethnic groups?

At the outset, answering these questions would appear to be a simple matter: at the same height and body weight, some people have a larger lean mass and smaller fat mass than others. But at another level, the answer is much more complex and delves directly into the nature of BMI and how this simple measure of shape relates to adiposity. The question arises as to the validity of these concepts both when BMI is applied to the individual level and when it is examined across race and ethnic groups.

In this review, we focus on the latter and less well-studied topic. Our review provides new and quantitative insights into the relationships between BMI, body shape and body composition across three adult race and ethnic groups.

Our analyses are also limited to between-race and age group body shape and composition differences; we do not delve into the broader question of individual subject differences in BMI—adiposity relations. Our review also does not address the issue of the statistical difficulty of finding the true value of height scaling exponents, which we recognize is a challenge for all allometric studies.

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We instead refer the interested reader to seminal manuscripts by Warton et al. Fortunately, though, most studies find height scaling exponents in the range of 1. These samples and analytical methods are described in Supporting Information II. reports of adiposity differences between race and ethnic groups often rely on relatively small samples, body composition methods of questionable accuracy and precision, use of different body composition methods and instruments across the evaluated race and ethnic groups, and they often include limited demographic descriptions of evaluated subjects 519 — If so, what is their magnitude?

Answering this question provides a baseline for the analyses that follow. These findings, consistent with earlier reports 3839show young adults of the same BMI but differing in race and ethnic group do have ificantly different levels of adiposity. While the findings in this example are consistent with the prevailing literature 3839a much more complex set of anatomic relationships is present between these three race and ethnic groups. One measure that reflects these potential exposure differences is stature, as adult height is strongly influenced by developmental diet and health status 40 As shown in the left-hand panels of Fig.

In addition Black or ethnic bbw underlying genetic mechanisms, these height differences likely reflect distinct patterns of nutritional, economic and social exposures to the populations under study. Height vs. If these population differences in stature are indeed because of potentially differential environmental exposures, the question arises if the aforementioned between-group differences in adiposity among young adults are stable across the adult lifespan.

While calculated tens of thousands of times every day, few of those applying BMI give much consideration to the complex mathematical and anatomical relations that are embodied in what has become the most widely used shape index on a global scale. One controversy arising related to BMI is that weight might scale to height with powers other than 2 1545 If this is the case, then adjusting weight for height 2 would lead to erroneous conclusions regarding adiposity comparisons across short and tall people However, there are at least two caveats regarding biological factors that may skew the scaling powers in a population sample.

First, many adults gain weight as they age and older adults are also often shorter than their younger counterparts because of secular effects and gradual vertebral bone loss A second concern relates to the presence of ificant correlations between adiposity and height in some population samples, even after taking age into consideration 17 Biological theories to Black or ethnic bbw this observation include accelerated growth in obese children with premature ossification of epiphyses leading to short adult stature 49 ; and MC4R-mediated influences on hypothalamic somatostatinergic tone leading to obesity and accelerated growth in children and obesity with tall adult stature For example, a sample of young adults may be characterized by high levels of both adiposity and body weight present in short subjects, 1718 and this effect will again influence the slope of log body weight vs.

A prevailing assumption, one important in developing static allometric models in the current context is that adiposity is biologically independent of height in the general population In sum, body weight empirically scaled to height across NH white, NH black and Mexican American men and women with powers of about 2, after controlling for adiposity and age. But do these findings mean that all people with the same BMI have an identical shape, independent of height? However, great heterogeneity exists in the body weight proportions of these different regions.

Do these four body mass regions all scale to height similar to body weight i. A region that scales with a height power different from 2 may not be the same proportion of body weight in tall vs. The regional mass scaling powers were derived using the same modeling approach as for body weight. Our regional mass-body composition DXA model described in this and in later sections is shown in Supplementary Fig. Head mass scaled with a low power of about 1, leg mass scaled with powers between about 2. Because body weight scaled to height in these subjects with a power of about 2, this means that taller people had a larger fraction of their body weight as leg mass and a smaller fraction as head mass than did their shorter NHANES counterparts.

Variation in regional body mass proportions with height may be one reason the shorter, younger Mexican American men and women groups might differ in relative body shape from the taller NH white and black groups. Residual mass includes all non-musculoskeletal lean tissues and organs Collectively, musculoskeletal mass skeletal muscle plus bone also scales to height with powers of about 2. By contrast, residual mass scales to height with powers of about 1. These new observations indicate that skeletal muscle and bone maintain relatively stable relations to each other as a function of stature and that taller subjects have a larger fraction of their FFM and body weight as those two components than do shorter subjects of equivalent age and adiposity.

Viewed from another perspective, and combining these findings with our earlier observations, taller people have a larger fraction of their body weight in their legs and a larger fraction as skeletal muscle and bone than do shorter people of the same BMI. Similarly, taller people have a smaller fraction of their body weight as residual mass, the component that includes all non-musculoskeletal lean tissues and Black or ethnic bbw.

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This observation is consistent with the finding that some organs and tissues that comprise residual mass scale to height with very low powers. For example, brain mass scales to height in both men and women with powers of one or less Among body circumferences, waist circumference is the most useful to evaluate in research and clinical settings because it is used as a measure of total body fat, visceral fat and as a marker of metabolic risk From an anatomical perspective, waist circumference encircles adipose tissues, skeletal muscles, bones and visceral organs.

If waist circumference increased isometrically with stature, taller people would have a much larger waist circumference than is actually observed. Isometric Black or ethnic bbw of the waist as a function of stature would be characterized by a height scaling power of one. As an example, if adult A was twice the height of adult B, their waist circumference would also be twice as large.

However, waist circumference actually increases across adults approximately as Ht 0. Of note, we also found similar height scaling patterns in Korean Asians 17 The selection of this sample and related analysis methods are described in Supporting Information II 17 We then examined whether body shape regional body mass proportions and composition skeletal muscle, bone, residual mass, FFM and fat mass differs across the BMI and height-matched NH white, NH black and Mexican American subjects within each sex and age group.

Regional body mass and whole-body composition for the demonstration sample are presented in Table 2 for men and Table 3 for women. The tables provide statistical comparisons between the groups, and for convenience, here we report only statistically ificant differences in the text, unless otherwise noted. These differences arise from variation between the groups in relative body shape and aspects of body composition even though the groups for each sex are similar in age, BMI, height and weight.

Nonetheless, this pattern of body composition differences was the same in both NH black men and women: the larger FFM than NH white and Mexican American subjects reflects the net ificant differences between greater musculoskeletal mass and smaller residual mass. On average, Mexican American subjects had more of their body mass stored in the trunk region, with the exception that the differences between Mexican American men and NH white men were non-ificant. The Mexican American subjects also had less appendicular mass, but statistical ificance was present only for comparison to the NH blacks.

The Mexican American men and women had less musculoskeletal muscle mass and the same or less residual mass as NH whites or NH blacks, respectively. Important anatomic changes occur as people age, with older and younger adults having different body shape and composition Relative to the younger subjects, the older NH white subjects had less body mass in their legs and more in their trunk; small and inconsistent differences are present in head and arm mass. Patterns of between-age group differences in regional body mass and composition with younger NH white men and women as the referent groups.

Positive or negative values indicate, respectively, larger or smaller relative amounts of regional mass, bone, skeletal muscle SMresidual mass RMfat-free mass FFM or fat Black or ethnic bbw present in the older NH white group compared with the corresponding younger NH white groups.

Black or ethnic bbw

Investigators comparing body shape and composition phenotypes across race and ethnic groups face a formidable challenge in separating out what might constitute inherited vs. Likewise, environmental differences between the evaluated groups are probably substantial.

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Importantly, developmental nutrition and health factors strongly influence adult stature, body shape and body composition 60 We have tried to tease apart some of these factors in our analyses but interpretation of our findings requires consideration of the multiple complexities when reviewing potential biological mechanisms. These differences are most consistent and apparent in younger adults but to some extent are present in older age.

BMI in this context is thus a measure of adult shape that is independent of height. We discovered that people who have the same BMI but who differ in height also differ in regional body mass and body composition proportions. Specifically, we found that taller adults who have the same BMI as shorter adults have a larger proportion of their body mass in their legs and as musculoskeletal mass and a smaller proportion in their head. Black or ethnic bbw similarly observed that waist circumference increases with stature as Ht 0. Importantly, regional body mass, body composition and waist circumference show very similar height scaling patterns across NH white, NH black and Mexican American men and women.

Another observation, confirmatory of earlier studies 195762is that for the same BMI and height, older people have a different body shape and composition than younger people.

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Our findings on the NHANES demonstration sample show that relative to younger people of the same BMI and height, older adults have a smaller appendicular and musculoskeletal mass and a corresponding larger trunk and residual mass.

Our findings affirm the limitations of BMI as a measure of sarcopenia or age-related skeletal muscle loss Even though younger and older adults had the same average BMI, substantially less skeletal muscle and bone were present in the older adults. An important proviso is that even though we are comparing lean mass components across older and younger adults, Black or ethnic bbw present we have no way to ascertain the quality of these differences.

Specifically, with aging lean tissues proportionally increase in connective tissue and structural proteins and for skeletal muscle there are greater relative losses of type II vs. Thus, our observed anatomic differences between older and younger adults may not translate directly to age-related functional effects.

The larger relative trunk mass and waist circumference in older adults reveals that waist circumference and BMI are not perfectly coupled, the two often contrasted as measures of health risk The larger trunk mass in older adults of the same BMI represents net differences from younger adults in total adipose tissue, skeletal muscle, bone and even the relatively larger total residual organ and tissue mass.

Senescence is also accompanied by enlargement of visceral adipose tissue, and this small but metabolically important compartment also likely contributes to the greater waist circumference observed in older adults Compared with the matched NH white and Mexican American subjects, greater musculoskeletal mass and less residual mass combined to create a net same or larger FFM in all of the NH black groups.

These body composition effects were accompanied by correspondingly greater leg mass and smaller trunk mass and waist circumference in NH blacks, with the one exception of a larger waist circumference in the older NH black women. Merz et al.

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