"It is important for men to be aware that excess belly fat is not only a risk factor for heart disease and diabetes, it is also a risk factor for bone loss," said Miriam Bredella, radiologist at Massachusetts General Hospital and associate professor of radiology at Harvard Medical School in Boston.
"Most studies on osteoporosis have focused on women. Men were thought to be relatively protected against bone loss, especially obese men," Bredella said.
Subcutaneous fat lies just below the skin, and visceral or intra-abdominal fat is located deep under the muscle tissue in the abdominal cavity.
Excess visceral fat is considered particularly dangerous, because in previous studies it has been associated with increased risk for heart disease.
A multi-center observational study designed to determine risk factors for osteoporosis - indicated that male obesity was associated with fracture risk, the researchers wanted to quantify belly fat and study its impact on bone strength.
Bredella and her team evaluated 35 obese men with a mean age of 34 and a mean body mass index (BMI) of 36.5. The men underwent CT scan of the abdomen and thigh to assess fat and muscle mass, as well as very high resolution CT of the forearm and a technique called finite element analysis (FEA), in order to assess bone strength and predict fracture risk.
"FEA can determine where a structure will bend or break and the amount of force necessary to make the material break. We can now use FEA to determine the strength or force necessary to make a bone break," Bredella said.
The FEA analysis showed that men with higher visceral and total abdominal fat had lower failure load and stiffness, two measures of bone strength, compared to those with less visceral and abdominal fat. There was no association found between age or total BMI and bone mechanical properties.
"We were, however, surprised that obese men with a lot of visceral fat had significantly decreased bone strength compared to obese men with low visceral fat but similar BMI," Bredella said.
The results also showed that muscle mass was positively associated with bone strength.
