Cardiometabolic risk hinges on type, not amount, of fat in obese patients

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Cardiometabolic risk may hinge less on body fat mass and more on where in a patient’s body that fat is stored, according to research presented this week at the Radiological Society of North America's annual meeting in Chicago.

More than 70 percent of Americans are either overweight or obese, according to the National Center for Health Statistics, but the number on a patient’s scale doesn’t always reflect their health risks. Massachusetts General Hospital clinician Miriam A. Bredella, MD, presented two studies Tuesday, both of which emphasized fat distribution and type as independent predictors of cardiovascular disease risk.

Bredella’s first study focused on 200 overweight and obese individuals, the majority of whom were women and in their thirties. The patients, who all had similar BMIs, fasted overnight before undergoing dual-energy x-ray absorptiometry and computerized tomography (CT) scans to determine body composition. Each patient also underwent magnetic resonance spectroscopy for fat quantification and analysis.

“We hypothesized that there are gender-based differences in body composition and ectopic fat depots and that these could be associated with gender-specific risk profiles for diseases like diabetes, heart disease and stroke,” Bredella said in a press release.

Indeed, the study’s female patients recorded higher percentages of fat and subcutaneous fat with lower lean mass when compared to men, who showed more visceral adipose tissue, or ectopic fat depots, around their abdomens.

Men biologically tend to carry less fat and more muscle than women, Bredella explained, but ectopic fat—a dangerous subset that’s found predominantly in the abdomen, muscle, liver and other organs—wasn’t associated with higher cardiometabolic risk in the male patients. Women, on the other hand, saw a significant increase in risk with increased ectopic fat.

“The detrimental fat depots deep in the belly, muscles and liver are more damaging for cardiometabolic health in women compared to men,” Bredella said.

In her second trial, Bredella and her team also found that young adults, particularly women, with low muscle mass in relation to BMI were at a higher risk for cardiometabolic disease.

“Sarcopenic obesity may be an underappreciated mechanism linking obesity to cardiometabolic disease,” Bredella said of the condition. “That stresses the importance of building up muscle mass in the setting of obesity.”