Not All Fat Contributes Equally To Metabolic Syndrome Risk Interview with:
Venkatesh L. Murthy, MD, PhD
Department of Medicine (Cardiovascular Medicine Division) and Department of Radiology (Nuclear Medicine and Cardiothoracic Imaging Divisions),
University of Michigan, Ann Arbor, Michigan and

Dr. Ravi Shah MD
Cardiology Division, Department of Medicine
Massachusetts General Hospital, Boston, Massachusetts

Medical Research: What is the background for this study? What are the main findings?

Response: Prior studies in Framingham, MESA and other cohorts have demonstrated that obesity is an important risk factor for the metabolic syndrome. However, the observations that many non-obese individuals develop metabolic syndrome and diabetes and, conversely, that not all obese individuals develop these complications has motivated the search for better markers of risk than BMI. More recently, it has been shown that the location of adipose tissue is an important factor. The amount of visceral fat, which is thought to be more harmful from a metabolic perspective, can be accurately quantified with CT imaging. In many prior studies, waist circumference has been used as an approximate measure of visceral adiposity.

For this study, we analyzed data from the Multi-Ethnic Study of Atherosclerosis (MESA). We found that the amount of visceral fat (as quantified by CT) was an important predictor of metabolic syndrome, even after adjusting for weight, waist circumference, gender, race, smoking, exercise, serum lipids and glucose. Each additional 100 cm2/m of height of visceral fat was associated with a 29% increase in the risk of developing metabolic syndrome. In contrast, subcutaneous fat burden (also quantified by CT) was a much weaker predictor.

One of the very novel findings of our study arises from an analysis of subjects who had multiple CTs longitudinally in MESA. Using these data, we found that change in visceral fat burden was associated with a corresponding 5% increase in the risk of metabolic syndrome. In part, this is because very small changes in weight could result in very large changes in visceral fat.

Medical Research: What should clinicians and patients take away from your report?

Response: Visceral fat is an important predictor of metabolic risk. While CT scans could be used to assess this in a way that might improve risk assessment over standard clinical measures such as weight and waist circumference, this is not yet widely feasible, but may be in the future. When patients gain (or lose weight), the change in the visceral fat compartment are far more important than changes in the subcutaneous fat compartment in terms of metabolic health.

Medical Research: What recommendations do you have for future research as a result of this study?

Response: The weight changes we saw over time were largely outside of organized medical and surgical weight loss programs. Consequently, most patients only had modest weight changes over the study period. It will be interesting to see how these data translate to cohorts losing large amounts of weight using surgical or medical strategies. This could offer insights into the metabolic benefits of these weight loss strategies