New MESA Data Show Obesity Is Not Inevitable

New MESA Data Show Obesity Is Not Inevitable  CME

News Author: Lisa Nainggolan
CME Author: Charles Vega, MD
Disclosures

Release Date: May 14, 2008; Valid for credit through May 14, 2009

Credits Available

Physicians - maximum of 0.25 AMA PRA Category 1 Credit(s)™ for physicians; Family Physicians - up to 0.25 AAFP Prescribed credit(s) for physicians

To participate in this internet activity: (1) review the target audience, learning objectives, and author disclosures; (2) study the education content; (3) take the post-test and/or complete the evaluation; (4) view/print certificate View details.

Learning Objectives

Upon completion of this activity, participants will be able to:

1. Specify ethnic groups in the United States at increased risk for obesity.
2. Describe the effect of obesity on subclinical vascular disease among different ethnic groups.

Authors and Disclosures

Lisa Nainggolan
Disclosure: Lisa Nainggolan has disclosed no relevant financial relationships.

Charles Vega, MD
Disclosure: Charles Vega, MD, has disclosed an advisor/consultant relationship to Novartis, Inc.

Brande Nicole Martin
Disclosure: Brande Nicole Martin has disclosed no relevant financial information.

 

From Heartwire — a professional news service of WebMD

May 14, 2008 — 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."

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 low-density lipoprotein (LDL)-cholesterol 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."

Black, white, or Hispanic? For BMI, it's all the same

Burke and colleagues analyzed data from MESA, which involved 6814 individuals aged 45 to 84 who did not have cardiovascular disease (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."

Coping with obesity by treating high BP, dyslipidemia, and diabetes

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 left ventricular 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 United States. "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."

The authors have disclosed no relevant financial relationships.

Source

1. Burke GL, Bertoni AG, Shea S et al. The impact of obesity on cardiovascular disease risk factors and subclinical vascular disease. The multi-ethnic study of atherosclerosis. Arch Intern Med. 2008;168:928-935.

The complete contents of Heartwire, a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

Clinical Context

The prevalence of obesity has increased significantly in the United States in the last several decades. Data from 2000 demonstrate that 28% of men and 34% of women can be considered obese. The obesity epidemic exacts a terrible toll in terms of consequences for public health. The direct costs of obesity total more than $90 billion annually in the United States, and there is a possibility that obesity will curtail any advances in average longevity among US adults.

Although the problem of obesity is now receiving significant attention, the prevalence of obesity in minority ethnic populations and its effect on the cardiovascular risk of these patients has not been as well-studied. The current report from MESA addresses these issues.

Study Highlights

• Individuals eligible for study participation were between the ages of 45 and 84 years and identified themselves as white, African American, Hispanic, or Chinese American. Individuals with a history of existing cardiovascular disease or who were morbidly obese were excluded from study participation.
• Participants underwent a baseline evaluation to determine their medical history, BMI, blood pressure, and serum lipid and glucose values.
• Subjects also underwent measurements of coronary calcium using computed tomography; carotid IMT, using B-mode ultrasound; and left ventricular mass, using magnetic resonance imaging.
• The main study outcome was the prevalence of obesity in the different ethnic groups and the effect of obesity on coronary calcium, carotid IMT, and left ventricular mass. The latter result was adjusted to account for traditional cardiovascular risk factors.
• More than 50% of African American women were obese compared with 40% of Hispanic women and nearly 30% of white women.
• The rate of obesity among both African American and Hispanic men was 30%, with the prevalence of obesity among white men being slightly less than 30%.
• In contrast, only 5% of Chinese-American participants were considered obese.
• Higher BMI had adverse effects on blood pressure, lipids, and glucose levels. This was evident despite the finding that overweight and obese subjects were more likely to receive antihypertensive and hypoglycemic medications.
• Ethnicity did not significantly modify the positive relationship between BMI and blood pressure and prevalence of glucose intolerance, with the exception that overweight and obese Chinese American women did not have a significantly elevated risk for glucose intolerance compared with women at a normal weight.
• Obesity was associated with a 20% greater prevalence of a positive coronary artery calcium score compared with normal weight.
• Obesity increased the risk for a finding of internal carotid IMT above the 80th percentile by 32% compared with normal weight, and the respective increase for obese vs normal weight subjects in the outcome of elevated common carotid IMT was 45%.
• The risk for an elevated left ventricular mass was also increased among obese vs normal weight individuals.
• There was generally no interaction between ethnicity and the increased burden of subclinical vascular disease associated with obesity.
• The authors note that because their research excluded patients with cardiovascular disease and the morbidly obese, their current study could underestimate the prevalence of cardiovascular disease associated with obesity.

Pearls for Practice

• In the current study, Chinese Americans had a significantly lower prevalence of obesity compared with whites, Hispanics, and African Americans.
• The current study finds that ethnicity does little to alter the positive correlation between obesity and carotid IMT, left ventricular mass, and coronary artery calcification