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Fatty Muscles Increase Heart Disease Risk
  • Posted January 23, 2025

Fatty Muscles Increase Heart Disease Risk

A well-marbled steak is highly prized for grilling, but those sort of fat deposits in human muscles can be deadly, a new study says.

People with pockets of fat hidden within their muscles have a higher risk of dying from heart-related health problems, researchers reported in a study published Jan. 20 in the European Heart Journal.

For every 1% increase in fatty deposits in muscle, there was a 7% increased risk of heart-related death, heart attack or heart failure, researchers found.

Even people with a healthy BMI can have these hidden fat deposits within their muscles, researchers said. (BMI is short for body mass index, an estimate of body fat based on height and weight.)

In fact, the heart risk associated with fatty muscle was independent of BMI and other known heart risk factors, results show.

“Knowing that intermuscular fat raises the risk of heart disease gives us another way to identify people who are at high risk, regardless of their body mass index,” senior researcher Dr. Viviany Taqueti, director of the Cardiac Stress Laboratory at Brigham and Women’s Hospital in Boston, said in a news release.

For the study, researchers performed imaging scans on nearly 670 patients being evaluated at Brigham and Women’s Hospital for chest pain or shortness of breath.

CT scans were used to assess how well the patients’ hearts were functioning. The scans also measured the amounts and location of fat and muscle in their torso.

The research team created a measurement called the “fatty muscle fraction” to quantify the amount of fat hidden within each patient’s muscles.

“Intermuscular fat can be found in most muscles in the body, but the amount of fat can vary widely between different people,” Taqueti said.

The patients then were followed for about six years to see whether they died or were hospitalized for a heart attack or heart failure.

It turned out that people with more fat in their muscles were more likely to suffer damage to the tiny blood vessels that serve the heart, a condition called coronary microvascular dysfunction (CMD).

The risk of CMD rose 2% for every 1% increase in fatty muscle fraction, researchers said. 

People who had high levels of fatty muscle and evidence of CMD were at especially high risk of death, heart attack and heart failure, results show. 

On the other hand, people with higher amounts of lean muscle had lower risk, and fat stored under the skin did not increase risk.

“Compared to subcutaneous fat, fat stored in muscles may be contributing to inflammation and altered glucose metabolism leading to insulin resistance and metabolic syndrome,” Taqueti said.

“In turn, these chronic insults can cause damage to blood vessels, including those that supply the heart, and the heart muscle itself,” Taqueti added.

The results add evidence to the growing contention that measures like BMI or height-to-waist circumference are not adequate for accurately evaluating heart disease risk in all people, researchers said.

Unfortunately, it’s not yet known how to lower heart risk for people with fatty muscle, Taqueti said.

“For example, we don’t know how treatments such as new weight-loss therapies affect fat in the muscles relative to fat elsewhere in the body, lean tissue, and ultimately the heart,” Taqueti said.

More information

Harvard T.H. Chan School of Public Health has more on body fat.

SOURCE: European Heart Journal, news release, Jan. 20, 2025

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