Winston-Salem, NC - A new analysis of the Multi-Ethnic Study of Atherosclerosis (MESA) has found that while 30% to 50% of blacks, whites, and Hispanics are obese, only 5% of Chinese Americans are [1]. The data document the widespread epidemic of overweight and obesity across most racial/ethnic and age groups and among both sexes, say Dr Gregory L Burke (Wake Forest University School of Medicine, Winston-Salem, NC) and colleagues in the May 12, 2008 issue of the Archives of Internal Medicine.

Burke told heartwire: "The key finding is that the alarming rates of obesity that we are getting used to seeing are present here—and remember, this is a group of folks who were free of any cardiovascular disease at baseline. Our metric has changed, society has shifted up to an acceptance level of obesity, but when you bring in the Chinese Americans, it reminds us that those set points are wrong—obesity is not inevitable."

Society has shifted up to an acceptance level of obesity, but . . . obesity is not inevitable.

Burke and colleagues also assessed the association of obesity with traditional cardiovascular risk factors and with subclinical vascular markers. They found a higher body-mass index (BMI) was associated with more adverse levels of blood pressure (BP), lipids, and fasting glucose and more subclinical disease despite a high prevalence of pharmacologic treatment for these disorders.

"Fifteen to 20 years ago, people said obesity was not an independent risk factor for heart disease, and when they did that, they basically said that obesity doesn't matter because all you need to do is treat their hypertension, and if their LDL is high, treat that, and have them not smoke and they're going to be okay," Burke continued. "What we are finding is that that's not true. For the first time in human history we are seeing a generation with a lot of obesity age into older adulthood, where we often see a lot of chronic diseases. The ability of the medical care system to treat that many people—it just doesn't work."

Burke and colleagues analyzed data from MESA, which involved 6814 individuals aged 45 to 84 who did not have CVD when the study began (2000 to 2002). They assessed the association between body size and CVD risk factors, medication use, and subclinical vascular disease by measuring coronary artery calcium (CAC), carotid artery intima media thickness (IMT), and left ventricular mass.

A large proportion of white, African American, and Hispanic participants were overweight (60% to 85%) or obese (30% to 50%), while fewer Chinese Americans were overweight (33%) or obese (5%).

Burke commented: "For an awfully long time we have been looking at data from Hispanics, whites, and African Americans and saying, 'Well, you know, black women have greater obesity than white women,' but when you throw the Chinese into the equation, those three groups actually look very similar; they look almost identical. We see huge amounts of obesity in the other racial ethnic groups [apart from the Chinese] that are not acceptable."

The Chinese in this study were, by and large, relatively recent immigrants, he added. "What we've learned from migrant studies is that it takes a few generations for immigrants to adopt the behaviors of their new environment."

Hypertension and diabetes were more prevalent in obese participants despite a much higher use of antihypertensive and/or antidiabetic medication, and obesity was associated with a greater risk of CAC (17%), common carotid IMT >80th percentile (45%) and LV mass greater than the 80th percentile (2.7-fold) compared with normal body size. These associations persisted after adjustment for traditional CVD risk factors.

"We are coping with the obesity epidemic by having 40% to 60% of our participants on BP-lowering meds, 20% on lipid-lowering meds, and 10% to 20% on insulin or oral hypoglycemics," says Burke, "and there are a couple of parts to that. First, it's costing society money." He and his colleagues estimate the direct costs of obesity to exceed $90 million annually in the US. "Second, the obesity epidemic looks set to reverse the 50-year decline in cardiovascular mortality that has been seen in the US and other Western countries." He adds that this is "infecting" the developing world too, where "the ability to have 40% to 50% of their population on antihypertensives is nil."

Burke says the fundamental issue is "of calories being cheap and the move toward a more sedentary society." And although there are many people trying to make a big difference in kids, he says it's almost as if people have "sort of given up on the older generation. In adults, the strategy is to just have us not get more obese, that it's a homeostatic mechanism and we can't change behaviors. But I don't buy that. It's tough, but we can change behaviors."