A recent study published in the European Heart Journal reveals that fatty deposits within muscles can significantly increase the risk of heart disease, independent of body mass index (BMI) or waist circumference. The findings challenge the long-standing reliance on BMI as a sole measure of heart health.
The study, which followed 669 individuals over the course of six years, highlighted the increased risk of heart attack, heart failure, and death in those with higher amounts of intermuscular fat. This fat, located within muscle tissue, was found to impair the tiny blood vessels that supply the heart, a condition known as coronary microvascular dysfunction (CMD). The presence of this dysfunction was associated with a heightened likelihood of hospitalization or mortality from heart disease.
Reevaluating Heart Disease Risk
Professor Viviany Taqueti, Director of the Cardiac Stress Laboratory at Brigham and Women’s Hospital in the United States, noted that the study provides new insights into identifying individuals at high risk for heart disease. “Knowing that intermuscular fat raises the risk of heart disease gives us another way to identify people at high risk, regardless of their BMI,” said Taqueti.
The research used advanced CT scans to assess body composition, focusing on the distribution and quantity of fat and muscle in the torso. Researchers introduced a novel metric, the fatty muscle fraction (FMF), which measures the ratio of fat within muscles relative to total muscle and fat mass. Their findings were striking: a 1% increase in FMF was linked to a 2% rise in the risk of CMD and a 7% increased risk of severe heart disease.
In contrast, individuals with higher levels of lean muscle mass had a lower risk of cardiovascular issues. Subcutaneous fat, which is stored beneath the skin, did not exhibit the same detrimental effects as intermuscular fat.
Potential Mechanisms and Future Treatments
The researchers hypothesize that fat stored in muscles may contribute to inflammation and disrupt glucose metabolism, leading to insulin resistance and metabolic syndrome. These factors could, in turn, damage blood vessels, including those supplying the heart, as well as the heart muscle itself.
The findings are particularly relevant in light of the growing interest in fat- and muscle-modifying therapies, such as glucagon-like peptide-1 receptor agonists. These new treatments aim to reduce fat and increase muscle mass, offering potential benefits for heart health, according to Taqueti.
The team is now exploring various treatment strategies, including exercise, nutrition, weight-loss medications, and surgery, to mitigate the risks associated with fatty muscles and improve cardiovascular health.
As the study suggests, evaluating heart disease risk requires a more nuanced approach, one that goes beyond traditional measures like BMI, particularly in individuals with unusual body fat distributions.
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