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Study Challenges Concept of ‘Healthy’ Obesity

Subclinical coronary atherosclerosis found in obese subjects

According to an article in the April 30 issue of the Journal of the American College of Cardiology, some experts still doubt that obesity has an effect on overall mortality. Among the ideas behind such reservation is the concept of “metabolically healthy obesity.”

Defined as being in an obese state (body mass index [BMI] > 25 kg/m2) without demonstrable obesity-related metabolic abnormalities, such as dyslipidemia or impaired glucose tolerance, persons with “metabolically healthy obesity” are not believed to be in need of preventative therapies.

Challenging this concept, the new report compared the coronary artery calcium (CAC) scores of metabolically healthy obese and metabolically healthy normal-weight individuals to assess their respective risks of cardiovascular disease. The researchers found that an obese yet “metabolically healthy” state was associated with a greater prevalence of subclinical coronary atherosclerosis and cannot be considered a benign condition.

In their study, the authors defined a person’s metabolic health by the absence of fasting blood glucose ≥ 100 mg/dL (or the use of glucose-lowering agents); blood pressure ≥ 130/85 mm Hg (or the use of blood pressure-lowering agents); triglycerides ≥ 150 mg/dL (or the use of lipid-lowering therapies); high-density lipoprotein cholesterol < 40 mg/dL in men (or < 50 mg/dL in women); and a homeostasis model of insulin resistance ≥ 2.5.

The researchers evaluated 14,828 metabolically healthy Korean adults aged 30 to 59 years who had no known cardiovascular disease. The population was stratified into four categories: underweight (BMI < 18.5 kg/m2), normal weight (BMI 18.5 to 22.9 kg/m2), overweight (BMI 23.0 to 24.9 kg/m2), and obese (BMI ≥ 25 kg/m2).

Analyzing the CAC scores, the researchers found that the “metabolically healthy” obese group had a significantly greater prevalence of coronary atherosclerosis compared with their metabolically healthy, normal-weight counterparts. After making additional adjustments for metabolic risks factors and the low-density lipoprotein cholesterol level, however, it was found that this prevalence of subclinical coronary atherosclerosis in the “metabolically healthy” obese group no longer remained statically significant.

“Obese individuals who are considered ‘healthy’ because they don't currently have heart disease risk factors should not be assumed healthy by their doctors,” said lead author Yoo-soo Chang, MD. “Our research shows that the presence of obesity is enough to increase a person’s risk of future heart disease and that the disease may already be starting to form in their body. It’s important that these people learn this while they still have time to change their diet and exercise habits to prevent a future cardiovascular event.”

In a related editorial comment, Rishi Puri, MB, BS, of the Atherosclerosis Imaging Core Laboratory, writes that the new findings help dispel the idea that there is a level of obesity that is actually healthy, and “casts serious doubt on the concept of obese individuals maintaining a benign prognosis."

"Obesity adversely affects almost all physiological homeostatic mechanisms, and its presence is associated with both cardiac and many non-cardiometabolic disorders, including malignancy, infection, infertility, joint disease, depression, and cognitive decline," Puri comments. "Our society faces a monumental challenge to successfully tackle obesity and its complications. By labeling a subset of obese individuals as ‘metabolically healthy’ would undermine the ultimate task that physicians and health organizations face: to curb the current obesity epidemic and to prevent the next generation of individuals from becoming obese. Failure to promote weight-loss strategies to all obese individuals and to offer treatment only to obese patients with overt metabolic derangements would seem futile and short-sighted.”

Source: American College of Cardiology; April 30, 2014.

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