Date:

November 28, 2017

Source:

Radiological Society of North America

Summary:

It’s not
the amount of fat in your body but where it’s stored that may increase your
risk for heart attack, stroke and diabetes, according to a new study. The study
looked at the differences in fat distribution patterns among overweight and
obese men and women and their associated cardiometabolic risk.

It’s not the amount of
fat in your body but where it’s stored that may increase your risk for heart
attack, stroke and diabetes, according to a new study presented today at the
annual meeting of the Radiological Society of North America (RSNA). The study
looked at the differences in fat distribution patterns among overweight and
obese men and women and their associated cardiometabolic risk.

According to the National
Center for Health Statistics, more than 70 percent of Americans are considered
overweight or obese. Obesity puts individuals at risk for a variety of health
problems, and is the second leading cause of preventable death in the U.S.

However, people of the
same weight or body mass index (BMI) may have very different risk profiles,
based on genetics, lifestyle and diet. In addition, body composition differs
between men and women, with women having proportionately more fat and men having
more muscle mass.

Fat distribution is an
important determinant of cardiometabolic risk. Most people have heard the
phrases “apple-shaped” and “pear-shaped.” These are common
descriptors of human body shapes, based on where fat tends to be stored in the body.
In apple-shaped bodies, fat is distributed largely around the midsection, while
in pear-shaped bodies, fat is distributed lower around the hips and thighs. The
type of fat stored also plays a role in cardiometabolic risk. One type of fat
— ectopic fat — is particularly dangerous. It may be found in places such as
the abdominal region, muscles, liver and other organs.

“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,” said lead author
Miriam A. Bredella, M.D., radiologist at Massachusetts General Hospital and
associate professor of radiology at Harvard Medical School in Boston.

For the study, Dr.
Bredella and colleagues recruited 200 young (mean age 37), overweight and obese
individuals who were otherwise healthy. Of the 200, 109 were women and 91 were
men. Women and men were of a similar age and BMI.

After fasting overnight,
the study participants underwent dual-energy x-ray absorptiometry (DXA) and CT
scans to determine body composition, as well as magnetic resonance spectroscopy
(MRS) for fat quantification and analysis.

The results showed that
the women had a higher percentage of fat and more subcutaneous (below-the-skin)
fat but lower lean mass, compared to men. However, men had more visceral
adipose tissue (VAT), or ectopic fat depots located in the abdomen around the
internal organs (commonly known as a “beer belly”), and more ectopic
fat in the muscles and liver.

“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,” Dr Bredella said. “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.”

Compared to women, men
had higher measures of cardiometabolic risk overall, but ectopic fat was not
significantly associated with cardiometabolic risk in men. Ectopic fat in
women, however, was strongly associated with cardiometabolic risk measures.

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

In a related study
presented by Dr. Bredella today at RSNA 2017, the researchers looked at the
relationship between sarcopenic obesity — or the loss of skeletal lean muscle
mass in the presence of obesity — and its relationship to cardiometabolic
risk.

Many factors can lead to
sarcopenic obesity in young adults, particularly obesity and lack of exercise.

“But there are also
hormonal abnormalities,” Dr. Bredella said, “such as low growth
hormone secretion in individuals with abdominal obesity. Growth hormone helps
to build muscle mass. Nutrition also plays an important role, and too little intake
of protein can lead to muscle loss.”

The researchers studied
188 young, overweight and obese adults who were otherwise healthy. Participants
underwent DXA and CT scans and various metabolic tests. Results showed that
having a lower lean muscle mass to BMI ratio was associated with
cardiometabolic risk, and these effects were stronger in women than in men.

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

Story Source:

Materials provided by Radiological Society of North America.
Note: Content may be edited for style and length.

Radiological
Society of North America. “Fat distribution in women and men provides
clues to heart attack risk.” ScienceDaily. ScienceDaily, 28 November 2017.