Comparison of minority and white populations by aspects of obesity emphasizes important minority health issues and poses certain challenges for future obesity research. This report provides a brief overview of these issues and challenges.

Prevalence

Data for non-Hispanic whites give the impression that obesity affects approximately one in four adults [2]; however, as shown in Figures 1 and 2, the prevalence of obesity is far greater in many minority populations, in some cases exceeding the prevalence among whites by three times. The estimates in the figures are for adults 20 to 74 years old [2, 3], except for Native Hawaiians (20 to 59 years old) [4] and American Indians (18 years and older) [5]. The markedly high prevalence of obesity is more pronounced in women than in men and, in these data, is most pronounced in Pacific Islanders (for example, Native Hawaiians and Samoans outside of Western Samoa). Obesity prevalence rates for some American Indian tribes are higher than those reported in the overall survey of American Indians and Alaska Natives [5]. In a survey of 20- to 74-year-old Pima Indians, for example, the age-specific prevalence of overweight ranged from 31% to 78% in 20- to 74-year-old men and from 60% to 87% in women [6]. A survey of Navajo adults (20 to 98 years old) indicated that 30% of men and 50% of women were overweight [7]. Figures 1 and 2 show that a substantial proportion of the overweight in these minority groups is severe.

View larger version (25K): [in this window] [in a new window]   Figure 1. Prevalence of overweight among adult men in U.S. minority populations. Data are from references 2-5 and use the same criteria of overweight (body mass index 27.8 kg/m2) and severe overweight (body mass index 31.1 kg/m2). The estimates for American Indians and Alaska Natives are based on self-reported data. (Reprinted with permission from Proceedings of Fifth Annual Nutrition Workshop, 30 October-1 November 1991, Meharry Medical College, Nashville, Tennessee [In press].).

View larger version (26K): [in this window] [in a new window]   Figure 2. Prevalence of overweight among adult women in U.S. minority populations. Data are from references 2-5 and use the same criteria of overweight (body mass index 27.3 kg/m2) and severe overweight (body mass index 32.2 kg/m2) for persons 18 or 20 years of age and older. The estimates for American Indians and Alaska Natives are based on self-reported data. (Reprinted with permission from Proceedings of Fifth Annual Nutrition Workshop, 30 October-1 November 1991, Meharry Medical College, Nashville, Tennessee [In press].).

Body fat distribution is an additional dimension of obesity-related risk, somewhat independent of overall weight or total body fat. Upper-body fat, particularly intra-abdominal fat, has been associated with an increased risk for diabetes and cardiovascular diseases in several cohorts [10, 11], including several minority groups [12–16]. Ethnic differences in fat distribution imply additional obesity-related risk in at least some minority populations compared with whites [17, 18]. A greater tendency toward upper-body obesity, indicated by a high waist-to-hip ratio or by a high centrality index (ratio of the subscapular to triceps skinfold thickness), has been documented in black compared with white women (Table 1) [17] and in Mexican-Americans compared with whites regardless of sex (Table 2) [18]. Although some ethnic differences exist in skeletal characteristics and fat distribution patterns, the ethnic differences in overweight or obesity prevalence do not appear to be artifactual [19, 20].

High Burden of Obesity-related Diseases

Minority populations have a relatively higher prevalence of obesity-related diseases than do white populations, particularly regarding diabetes mellitus [2, 21]. For example, diabetes prevalence is 16% to 26% in 45- to 74-year-old Hispanic and black Americans compared with 12% in non-Hispanic whites in this age range [2]. The prevalence of diabetes among American Indians and Alaska Natives is estimated to be more than twice that in the general population [2], although substantial variation occurs across tribes. Non-insulin-dependent diabetes mellitus is estimated to affect about one half of Pima Indians 35 years and older [6].

Available data for black Americans also indicate a high prevalence of several other obesity-related diseases including cardiovascular diseases, cerebrovascular diseases, and osteoarthritis of the knee [21, 22]; however, the overall health impact of obesity-related diseases in minority populations is less clear. Where relevant data exist, obesity is associated with increased levels of cardiovascular risk factors in ethnic minorities [20]. These populations vary, however, in the extent to which hypertension, coronary heart disease, and stroke are more prevalent than among whites [21], and even the increased occurrence of diabetes in minority populations does not simply parallel the excess prevalence of obesity [21, 23].

The significance of obesity for cause-specific and total mortality in minority populations has been particularly difficult to establish, especially in women [19, 24, 25]. The validity of direct comparisons of obesity-related mortality between minorities and whites is potentially reduced because of substantial differences in other mortality determinants such as infectious diseases, accidents, and homicide [2, 26]. Nonetheless, current evidence suggests that obesity may be less detrimental in certain minority populations than in whites and thus leads to questions about whether long-standing actuarial assumptions about obesity and mortality apply to minority groups. Such doubt then leads one to question whether the need for weight reduction applies to minority groups in the same way as to whites. Further, some evidence suggests that the tradeoffs associated with weight reduction may differ across populations. For example, black, Hispanic, and Asian American women have lower rates of osteoporotic hip fractures, for which obesity lowers risk, than do white women [19, 21]. Thus, the overall benefit-to-risk ratio of intervention to treat obesity may need to be evaluated objectively on a population-specific basis.

Weight Control Perspectives in Minority Populations

Several lines of evidence, including the lower prevalence of eating disorders among black women [27, 28], suggest that obesity among black or Hispanic women is associated with a lesser preoccupation with weight control, a lesser likelihood of perceiving oneself as overweight, and other "obesity-tolerant" attitudes that limit either the motivation for weight loss or the effectiveness of weight loss attempts [29–34]. This finding is to be expected if obesity is viewed from a social or anthropologic perspective as a culturally defined variable [35–37]. Simplistically, obesity will be viewed positively (or less negatively) within cultures, families, or generations for which it is associated with physical robustness and with protection from hunger. Equating thinness with beauty generally applies to women in economically advanced societies. Thus, although minority women may be interested in dieting to lose weight [38, 39] and although weight control programs may be well received in minority communities [40, 41], the prevalence of practices and skills needed to support long-term weight control may be limited in these communities [42, 43]. Also, conventional weight loss treatment models may be less effective among minority women than among white women [44, 45].

Future Research Perspectives

All aspects of the causes of obesity and treatment require more study in specific minority populations and among minorities in general. Data on obesity prevalence and health effects should be expanded to include subgroups that are not represented in national health surveys (for example, Asians and Pacific Islanders and American Indians). Such data should also include body fat distribution subtypes for all groups. For both adult and pediatric obesity, the influence of ethnic differences in stature and body conformation should also be clarified so that remaining questions about the appropriateness of using universal standards to define obesity can be resolved.

Research in minority populations is particularly needed in the areas of biological and cultural determinants of weight gain, the ability to lose weight, behavioral aspects of weight reduction, and any possible negative health consequences (physical or psychological) of weight cycling or weight reduction. Given the high prevalence of obesity in most minority populations, large proportions of these populations would presumably be targeted for programs aimed at weight reduction or at the prevention of weight gain and consequently would be vulnerable to exploitation or mismanagement based on inadequate or inappropriate approaches. No matter how great the apparent mandate for weight reduction in minority populations, effective weight reduction methods with proven benefit are necessary to support relevant public education, public policies, and treatment guidelines. One critical issue within this sphere centers on the development of obesity prevention strategies (for example, targeting adolescent and young adult women with weight control education programs) that do not simply push minority populations toward eating disorders.

Two additional general needs can be identified concerning approaches to this type of research. First, it is necessary to identify assumptions about cultural factors in obesity causation and treatment that determine who is studied, what kinds of questions are asked, how questions are asked, and how the resulting data are interpreted. Sociocultural variables for which the validity of certain majority population-based assumptions can be challenged include attitudes toward food; food preferences; body image (that is, desired body size and shape); negative and positive attitudes toward obesity by sex, age, and social status; attitudes toward physical activity, social aspects of eating, family relationships, and physical attractiveness; spending priorities; living arrangements; and support systems [45, 46].

Belief in the "melting pot" in which ethnic minorities would assimilate toward the dominant, Anglo-Saxon culture may have hindered recognition of the many fundamental differences in the norms, values, and world views of different ethnic groups in the United States. These differences clearly exist, however, among minorities as well as among white ethnic subgroups [47, 48] and must be understood as the context for behaviors that affect obesity and related health outcomes. The most difficult step for researchers may be to recognize that assumptions about certain factors that may be perceived as universal are, in fact, assumptions based on the dominant cultural framework. Subsequently, the integration of ethnographic and other qualitative research methods with quantitative approaches to design culturally appropriate studies in minority populations may pose another set of challenges. These challenges may be the greatest for those researchers who are the most expert in the conventional approaches.

More attention must be given to time trends in obesity-related risk factors, diseases, and health-related attitudes [26]. Cross-sectional comparisons between minorities and whites or among minorities should consider differences in patterns of disease occurrence and risk factors over time. Obesity appears to emerge as an early manifestation of economic advancement and of the conquest of epidemic undernutrition or infectious causes of mortality [49]. Obesity may begin to recede (through the increased practice of voluntary weight control) at a much later stage of economic stability and only after the harmful consequences of long-standing obesity have become entrenched and acknowledged. Both the health effects of obesity and the attitudinal and behavioral perspectives relevant to interventions may be affected by the slope, calendar period, and epidemiologic context for increases in obesity, respects in which minority populations are quite diverse.