Study Finds Fatty Muscles Raises Risk for Serious Heart Disease

You’re probably familiar with subcutaneous fat – the type of fat that settles under your skin that you can pinch. It usually accumulates in the thighs, hips, belly and buttocks. And you may have heard of visceral fat, the type that settles in the abdomen and wraps around internal organs.  

Some visceral fat is needed, as it protects organs, but too much can appear as a “spare tire” or “pot belly.” More importantly, visceral fat is an active fat, meaning that it can affect how well your organs function; too much raises the risk for high blood pressure, heart disease, diabetes and some cancers. But there’s another type of fat, which you might not be familiar with – it’s called intramuscular fat and plays an important role in your health.  

Intramuscular fat, also known as marbling fat, resides in the fibers of skeletal muscle fibers. Not a lot is known about it. Years ago, researchers linked excessive amount of with insulin resistance. More recently, researchers found that it raises the risk of hospitalization and death from a heart attack or heart failure, regardless of your body mass index, according to a study published in the European Heart Journal.

Researchers from Brigham and Women’s Hospital evaluated almost 700 patients with an average age of 63 who were experiencing chest pain and/or shortness of breath. A high percentage of patients were obese, 70 percent were women and 46 percent were non-White. Patients were assessed for obstructive coronary artery disease; had cardiac positron emission tomography/computed tomography (PET/CT) to analyze heart function; and a CT scan in a specific portion of the torso to determine the amount and site(s) of fat and muscle. Researchers also calculated the ratio of intermuscular fat to total muscle plus fat. This measurement is referred to as fatty muscle fraction and it was conducted to quantify the amount of stored fat in muscles.

After testing was completed, researchers ruled out obstructive coronary artery disease and followed up with patients six years later, documenting if patients had been hospitalized or passed away from a heart attack or heart failure. Moreover, researchers found that patients with heart disease had higher amounts of fat stored in their muscles that likely damaged tiny blood vessels that serviced the heart. This is referred to as coronary microvascular dysfunction (or CMD) and it raises the risk for heart disease and serious complications like heart attacks and heart failure. They also found:

• Every one percent increase in fatty muscle fraction raised the risk of CMD by two percent and the risk of future serious heart disease by a seven percent. This was regardless of other known risk factors, including body mass index.
• People who had high levels of intermuscular fat and CMD had a very high risk for heart attack, heart failure and heart-related death compared to those with higher amounts of lean muscle. Subcutaneous fat did not raise the risk.

Keep in mind, just because most of the patients in this study were female, doesn’t mean this is a women’s health issue. Intramuscular fat and CMD affects both men and women.  

More research is needed is to understand intermuscular fat and how to lower it. Currently, researchers are studying fat-reducing treatment strategies such as eating a healthy diet, exercising, taking weight-loss drugs or having surgery and the effects they have on body composition and metabolic heart disease. Future studies also may incorporate variables such as patients’ dietary habits, blood circulation and levels of inflammation, insulin resistance and fitness.

However, you probably don’t feel you need to wait for additional research. You can focus on controlling your body composition and insulin sensitivity. For example, you should:  

• Understand your body composition.
• Eat a heart healthy diet.
• Exercise regularly.
• Stay on top of inflammation levels.
• Prevent and/or manage insulin resistance and type 2 diabetes.
• Get enough sleep.

Most importantly, work with your primary care doctor. They can tailor lifestyle suggestions to meet your specific needs, and if necessary, prescribe treatment or refer you to specialist.