
A new study has found that people with fat hidden inside their muscles may have a higher risk of heart attacks, heart failure, or even death—regardless of their body weight.
This type of fat, called intermuscular fat, is different from fat under the skin or around the belly. The study was published in the European Heart Journal and is the first to explore how fat stored in muscles affects heart health.
What Is Intermuscular Fat?
Intermuscular fat is found between muscle fibers. While this fat is prized in beef steaks for its tenderness, its effects on human health are less understood. Unlike body fat that can be seen under the skin, intermuscular fat is hidden and cannot be easily measured by standard methods like body mass index (BMI) or waist size.
This study adds to growing evidence that BMI alone is not always a good measure of heart disease risk.
How the Study Was Conducted
The research was led by Professor Viviany Taqueti from Harvard Medical School and Brigham and Women’s Hospital in Boston. The study included 669 adults, with an average age of 63, who were being tested for chest pain or shortness of breath but had no blockages in their heart arteries. Most participants (70%) were women, and nearly half (46%) were non-white.
Doctors used advanced PET/CT scans to measure fat and muscle levels inside their bodies and to check how well their hearts were functioning. The participants were tracked for about six years to see if they developed heart problems, including heart attacks or heart failure.
Key Findings
Researchers discovered that people with higher amounts of intermuscular fat were more likely to have:
- Damage to small blood vessels in the heart (coronary microvascular dysfunction, CMD), which can lead to heart disease.
- A higher chance of serious heart problems, including hospitalization or death from heart failure or a heart attack.
For every 1% increase in intermuscular fat, the risk of CMD increased by 2%, and the risk of serious heart disease increased by 7%. These risks remained high even after considering other factors like BMI and traditional heart disease risk factors.
Why Does Muscle Fat Matter?
People with more lean muscle had a lower risk of heart problems, while fat stored under the skin (subcutaneous fat) did not increase heart disease risk.
Professor Taqueti explained that fat stored inside muscles may trigger inflammation and disrupt the body’s ability to process sugar properly. This can lead to insulin resistance and metabolic syndrome, which damage blood vessels and increase heart disease risk.
How Can This Information Help?
Understanding the dangers of intermuscular fat could help doctors better identify people at high risk of heart disease—especially those who may not appear overweight based on BMI alone.
Professor Taqueti and her team are now studying whether certain treatments, like exercise, diet changes, weight-loss medications, or surgery, can help reduce intermuscular fat and improve heart health.
The Bigger Picture
Experts agree that obesity is a major public health issue, but the relationship between weight and heart disease is complex.
An editorial by Dr. Ranil de Silva from Imperial College London, published alongside the study, emphasized that body composition matters more than just BMI. He noted that this study highlights how fat stored in muscles, not just overall weight, plays a role in heart disease risk.
However, the study had some limitations. It did not measure markers of inflammation, insulin resistance, diet, or exercise levels. More research is needed to confirm these findings and understand how intermuscular fat affects heart health over time.
Final Thoughts
This study provides new insight into how hidden fat in muscles may raise heart disease risk. While doctors traditionally focus on weight and BMI, measuring body composition—specifically fat stored in muscles—may be an important step in identifying and preventing heart problems.
For now, maintaining a healthy lifestyle with regular exercise, a balanced diet, and medical check-ups remains the best way to support heart health.
If you care about heart health, please read studies about top 10 foods for a healthy heart, and how to eat right for heart rhythm disorders.
For more health information, please see recent studies about how to eat your way to cleaner arteries, and salt and heart health: does less really mean more?
The research findings can be found in the European Heart Journal.
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