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Location of body fat may elevate CVD, cancer risk
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Individuals with excessive abdominal fat have a greater risk for CVD and cancer than individuals with a similar BMI who carry their fat in other areas of the body, according to new research.
“Contrary to previously published studies comparing BMI and waist circumference, the presence of abdominal fat improved the ability to predict for CVD, supporting the hypothesis that abdominal fat may partially underlie the association of body fat and heart disease and cancer,” Caroline S. Fox, MD, MPH, senior investigator at the National Heart, Lung and Blood Institute Laboratory for Metabolic and Population Health, said in a press release.
Researchers used CT scan to assess ectopic fat depots in the abdominal area — visceral adipose tissue, pericardial adipose tissue and periaortic adipose tissue — of 3,086 Framingham Heart Study participants. The participants’ mean age was 50 years and 49% were women.
During an average follow-up of 5 years, the researchers recorded 90 CV events, 141 cases of cancer and 71 deaths. Visceral adipose tissue was associated with incident CVD (HR=1.44; 95% CI, 1.08-1.92) and cancer (HR=1.43; 95% CI, 1.12-1.84) after adjustment for clinical risk factors and general obesity. The addition of visceral adipose tissue to a multivariable model that included BMI was linked with a modest improvement in CV risk prediction (net reclassification improvement, 16.3%). The researchers identified no link between fat depots and all-cause mortality, according to the abstract.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Edward S. Horton, MD
There has been a long-standing debate regarding whether the location of body fat is a significant determinant of the metabolic abnormalities, cardiovascular disease and increased risk of malignancies associated with obesity. In recent years, much evidence has accumulated that intra-abdominal or visceral fat deposition is associated with greater insulin resistance and compensatory hyperinsulinemia than is subcutaneous fat deposition. Increased intra-hepatic fat content is particularly important in this regard, and increased pericardial and periaortic fat are also associated with insulin resistance to a greater extent than is subcutaneous fat. In addition, visceral fat is an active producer of inflammatory cytokines, which may contribute to insulin resistance and vascular disease. Despite these known metabolic effects of central fat deposition, only a few cross-sectional, population-based studies, including data from the Framingham Study, have shown a significant difference in the risk for cardiovascular disease and obesity-related malignancies when comparing measurements of central obesity — such as waist circumference or waist/hip ratio — with overall obesity, generally measured as BMI. In contrast, numerous other studies have not found any significant differences in risk when comparing these commonly used measurements of central and overall obesity.
The current report, using longitudinal follow-up data from the Framingham Study and multi-detector computed tomography measurements of visceral, pericardiac and periaortic fat, now clearly demonstrates that visceral obesity is associated with a significantly greater risk of cardiovascular disease and malignancy than is generalized obesity, confirming what has been hypothesized from previous studies of its metabolic consequences. The potential roles of insulin resistance and hyperinsulinemia, chronic inflammation and other metabolic consequences of visceral obesity in the pathogenesis of these complications are being investigated in many laboratories, but much work still needs to be done to fully understand the pathogenic mechanisms involved. The findings in this report should provide added impetus to this work. In the meantime, this study demonstrates that visceral obesity is a better predictor of cardiovascular events and malignancies than is total obesity, although it is not a better predictor of all-cause mortality. For these reasons effective prevention and treatment of central obesity should become a major priority for clinicians and the population at large.
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