Increasing abdominal fat may be associated with newly identified and worsening cardiovascular disease risk factors, according to a study published Sept. 26 in the Journal of the American College of Cardiology.

Jane J. Lee, PhD, and colleagues examined 1,106 participants from the Framingham Heart Study. Over 6.1 years of follow-up, weight, body mass index (BMI), and waist circumference increased by 2.4 kg, 1.1 kg/m², and 3.7 cm, respectively. Participants gained an average of 602 cm³ of subcutaneous adipose tissue (SAT) volume and 703 cm³ of visceral adipose tissue (VAT) volume. The average fat attenuation decreased by 5.5 Hounsfield units (HU) for SAT and increased by 0.07 HU for VAT attenuation.

The authors found that increases in fat volume and decreases in fat attenuation were correlated with adverse changes in cardiovascular disease risk factor profiles. They also found weak to moderate correlations between changes in abdominal fat volume and attenuation with changes in cardiovascular disease risk factors. For each additional 500 cm³ increase in SAT and VAT volume, the odds of incident cardiovascular disease risk factors increased, with the exception of SAT volume change with diabetes mellitus, hypercholesterolemia, and low high-density lipoprotein cholesterol; and VAT volume change with impaired fasting glucose and diabetes mellitus.

For each additional five HU decrease in the change in SAT and VAT attenuation, the researchers found increased odds of incident cardiovascular disease risk factor profiles (p < 0.05), except for impaired fasting glucose and diabetes mellitus. Changes in abdominal fat volume and attenuation were associated with increased risk factors, and these adverse changes in cardiovascular risk were evident over a relatively short period of time and persisted even after accounting for changes in BMI and waist circumference.

Moving forward, the authors said more work needs to be done to understand fat density, and why and how it is associated with metabolic consequences of obesity (e.g., hypertension, abnormal cholesterol, diabetes, inflammation and insulin resistance). Also, it will be important to understand how less dense fat, along with simultaneous increases in the amount of fat may spur the development of harmful cardiometabolic changes.

In an editorial comment accompanying the study Ian J. Neeland, MD, and James A. de Lemos, MD, FACC, write that while there are a number of important questions that still need to be answered, these findings "support a growing body of data that clearly demonstrate that adipose tissue imaging, which allows anatomical characterization of regional fat depots, provides important information about cardiometabolic risk not contained in the simple BMI measurement."

Keywords: Abdominal Fat, Body Mass Index, Cardiovascular Diseases, Cholesterol, Diabetes Mellitus, Fasting, Follow-Up Studies, Glucose, Hypercholesterolemia, Hypertension, Inflammation, Insulin Resistance, Intra-Abdominal Fat, Lipoproteins, HDL, Obesity, Research Personnel, Risk Factors, Subcutaneous Fat, Waist Circumference

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