Some Obese Patients Appear Metabolically Healthy Without Increased Cardiovascular Risk

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Title: Some Obese Patients Appear Metabolically Healthy Without Increased Cardiovascular Risk
URL: http://www.pslgroup.com/dg/2280EA.htm
Doctor's Guide
August 11, 2008

CHICAGO -- August 11, 2008 -- Some obese individuals do not appear to have an increased risk for heart disease, while some normal-weight individuals experience a cluster of heart risks, according to 2 reports in the Archives of Internal Medicine.

Research indicates that in addition to overall obesity, the way body fat is distributed may influence risk for heart disease and diabetes. Norbert Stefan, MD, and colleagues at the University of Tubingen, Tubingen, Germany, tested this theory by studying 314 individuals aged 18 to 69. The researchers measured participants' total body fat, visceral fat, subcutaneous fat, and insulin resistance. The individuals were then divided into 4 groups: normal weight, overweight, obese but still sensitive to insulin, and obese with insulin resistance.

Those in the overweight and obese groups had more total body and visceral fat than those at a normal weight, and there was no difference between obese groups. However, obese individuals with insulin resistance had more fat within their skeletal muscles and their livers than obese individuals without insulin resistance. In addition, those who were insulin-resistant had thicker walls in their carotid arteries.

Individuals in the obese insulin-sensitive group did not differ from the normal-weight group in insulin sensitivity or artery wall thickness, the authors noted. "In conclusion, we provide evidence that a metabolically benign obesity can be identified and that it may protect from insulin resistance and atherosclerosis. Furthermore, our data suggest that ectopic fat accumulation in the liver may be more important than visceral fat in the determination of such a beneficial phenotype in obesity."

In a second study, Rachel P. Wildman, PhD, Albert Einstein College of Medicine, Bronx, New York, and colleagues assessed body weight and cardiometabolic abnormalities in 5,440 individuals participating in the National Health and Nutritional Examination Surveys between 1999 and 2004. Participants were considered metabolically healthy if they had none or 1 abnormality and metabolically abnormal if they had 2 or more abnormalities.

"Among US adults 20 years and older, 23.5% of normal-weight adults were metabolically abnormal, whereas 51.3% of overweight adults and 31.7% of obese adults were metabolically healthy," the authors noted. Normal-weight individuals with metabolic abnormalities tended to be older, less physically active, and have larger waists than healthy normal-weight individuals. Obese individuals with no metabolic abnormalities were more likely to be younger, black, more physically active, and have smaller waists than those with metabolic risk factors.

"These data show that a considerable proportion of overweight and obese US adults are metabolically healthy, whereas a considerable proportion of normal-weight adults express a clustering of cardiometabolic abnormalities," the authors explained. "Further studies into the behavioural, hormonal or biochemical, and genetic mechanisms underlying these differential metabolic responses to body size are needed and will likely further the identification of possible obesity intervention targets and improve cardiovascular disease screening tools."

SOURCE: Journal of the American Medical Association

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