As mentioned previously, the majority of interest in worsening prevalence of obesity is primarily due to the increased risk for future sequelae of T2DM and CVD. Thus, this discussion would not be complete without considering ethnic variation in the develop ment of adult disease. As suggested by the aforementioned data on elevations in BMI and WC, it may be expected that there would also be increased rates of future disease among various ethnic subsets. As we will see, the prevalence of both T2DM and CVD exhibit ethnic variation, suggesting that not all of the population carries the same risk. Nevertheless, the data on future disease do not entirely match up with expectations from obesity estimates.
The disease most closely associated with obesity is T2DM, which is marked by insulin resistance leading to a point at which insulin needs exceed its supply and blood sugars are elevated [23
]. T2DM is more common among both African–American and Hispanic adolescents and adults () [8
]. Among adolescents, African–Americans have an incidence of T2DM that is fourfold higher than that seen among non-Hispanic white children. The incidence of T2DM is approximately threefold higher among Hispanic children than non-Hispanic whites. In adulthood, this trend continues so that prevalence of T2DM among individuals >20 years of age is 12.8% among non-Hispanic blacks, 8.4% among Mexican–Americans and 6.6% among non-Hispanic whites [8
]. These trends hold true for males as well as females, which is at odds with the lower rates of central obesity among African–American men. Death rates from T2DM are more than twofold higher among African–American adults than white adults in each age category and Hispanic adults have rates 20–30% higher than whites [24
Ethnic differences in incidence of Type 2 diabetes.
It is important to note that even in T2DM, the major cause of obesity-related death is CVD. African–Americans have been found to have significant differences in cardiovascular physiology, including an increase in left ventricular wall thickness compared with whites at similar levels of blood pressure [25
]. This may be due to differences in peripheral vascular resistance, as demonstrated by multiple studies using ischemic occlusion, where the brachial artery is occluded by a blood pressure cuff and arterial measurements are made after blood flow is restored. When matched with whites for baseline blood pressure, African–Americans have less postocclusion dilation [26
], increased resistance [25
] and reduced overall blood flow [28
]. These findings have been hypothesized to be related to greater insulin release in African–Americans, as will be discussed in greater detail later [28
Death rates from CVD also exhibit ethnic discrepancies, with African–American men and women having higher rates of death from heart disease and cerebrovascular disease throughout adulthood, including twofold higher death rates than whites and Hispanics at each adult age category up to 65 years old [24
]. The reason for this elevated death rate is not clear, although higher rates of hypertension among African–Americans (discussed further later) and less access to medical care have been suggested [10