Visceral, or deep belly, obesity is a
risk factor for bone loss and decreased bone strength in men,
according to a study presented at the annual meeting of the
Radiological Society of North America (RSNA).
"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, M.D., radiologist at Massachusetts General Hospital and
associate professor of radiology at Harvard Medical School in
According to the National Center for
Health Statistics, more than 37 million American men over age 20 are
obese. Obesity is associated with many health problems, including
cardiovascular diseases, diabetes, high cholesterol, asthma, sleep
apnea and joint diseases. Yet despite all the health issues, it was
commonly accepted that men with increased body weight were at lower
risk for bone loss.
"Most studies on osteoporosis have
focused on women. Men were thought to be relatively protected
against bone loss, especially obese men," Dr. Bredella said.
But not all body fat is the same.
Subcutaneous fat lies just below the skin, and visceral or
intra-abdominal fat is located deep under the muscle tissue in the
abdominal cavity. Genetics, diet and exercise are all contributors
to the level of visceral fat that is stored in the body. Excess
visceral fat is considered particularly dangerous, because in
previous studies it has been associated with increased risk for
After the Osteoporotic Fractures in Men
Study—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.
Dr. 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 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 is a technique that is frequently
used in mechanical engineering to determine the strength of
materials for the design of bridges or airplanes, among other
things," Dr. Bredella said. "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."
In the study, 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
"We were not surprised by our results
that abdominal and visceral fat are detrimental to bone strength in
obese men," Dr. Bredella said. "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
The results also showed that muscle mass
was positively associated with bone strength.
Coauthors are Eleanor Lin, M.D., Mary L.
Bouxsein, Ph.D., Martin Torriani, M.D., Bijoy J. Thomas, M.D., Anu
V. Gerweck, N.P., and Karen Miller, M.D.
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