Almost 70 percent of people in the United States are overweight, and over a third of the population is obese. These dire statistics have led researchers and health professionals to speak of an obesity epidemic in the U.S.
Heart disease, stroke, and diabetes are only a few of the many cardiometabolic health risks associated with obesity. Coronary heart disease — for which obesity is a major risk factor — can lead to angina and heart attacks, if untreated.
But it's not so much the quantity of the fat that poses a threat to our health, as its distribution. For instance, we know that people with more fat around their abdomen tend to be predisposed to coronary artery disease.
Additionally, gender seems to play a role. New research suggests that gender influences how fat is distributed across the body, which, in turn, influences cardiometabolic risk.
Speaking about the motivation for her recent study, Dr. Bredella says, "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."
Their findings will be presented at this year's Radiological Society of North America annual meeting, held in Chicago, IL.
Studying sex, fat, and cardiometabolic risk
Dr. Bredella and team examined 200 overweight and obese but otherwise healthy adults. Ninety-one of the participants were male. All participants had a similar body mass index (BMI) and age — which was 37 years, on average.
In order to assess body composition, all the participants were examined using dual-energy X-ray absorptiometry and computed tomography scans after fasting overnight.
Using a technique called magnetic resonance spectroscopy, the researchers were able to quantify and examine the fat, determining levels of serum glucose, insulin, and lipids.
Dr. Bredella and colleagues performed linear regression analyses between body composition and the risk factors for cardiometabolic conditions.
The study revealed that women had more fat overall and more fat below the skin, but they also had lower lean mass than men. Lean body mass refers to the total weight of one's "muscles, bones, ligaments, tendons, and internal organs."
Men, however, had more of the so-called visceral adipose tissue, or ectopic fat, which are terms that describe fat that surrounds vital organs. Men had more ectopic fat in the muscles, abdomen, and liver.
Ectopic fat, sarcopenia affect women more
Dr. Bredella summarizes these findings, saying, "Obese men have relatively higher visceral fat, fat within muscle cells and liver fat, which are all risk factors for cardiometabolic disease, compared to women with the same BMI."
"However, men have higher muscle and lean mass, which are protective for cardiometabolic health. Women have a higher relative amount of total body fat and higher superficial thigh fat, which is protective for cardiometabolic health."
But surprisingly, ectopic fat did not increase the risk of cardiometabolic disease in men, while for women, the same ectopic fat correlated strongly with a high cardiometabolic risk. In other words:
"The detrimental fat depots deep in the belly, muscles, and liver are more damaging for cardiometabolic health in women compared to men."
Dr. Miriam A. Bredella
A similar study presented and led by the same Dr. Bredella examined the relationship between sarcopenic obesity and cardiometabolic health. Sarcopenic obesity refers to an unhealthful combination of low muscle mass and high fat mass.
This study, too, found that sarcopenic obesity was associated with a higher cardiometabolic risk, especially in women.
"Sarcopenic obesity may be an underappreciated mechanism linking obesity to cardiometabolic disease," Dr. Bredella explains. "That stresses the importance of building up muscle mass in the setting of obesity."