Obesity has long been recognized as a significant threat to cardiovascular health, but a recent study suggests that the fat stored in muscles may be an even more dangerous contributor to heart disease than previously thought. Conducted by researchers at Brigham and Women’s Hospital in the United States, the study highlights how an increase in muscle fat could lead to a greater risk of heart disease, particularly coronary microvascular dysfunction and severe cardiovascular conditions.
The study, published in the European Heart Journal, examined nearly 670 individuals with no obstructive coronary artery disease. Participants, most of whom were women, were assessed at the hospital for symptoms such as chest pain and shortness of breath. Researchers found that a one-percent increase in muscle fat was linked to a two-percent rise in the risk of coronary microvascular dysfunction, which occurs when small blood vessels in the heart malfunction. The risk for serious heart disease rose by as much as seven percent with every additional percent of muscle fat.
The findings challenge the reliance on traditional metrics like Body Mass Index (BMI) and waist circumference as accurate indicators of heart disease risk. According to the study, these conventional measures may not fully capture the risk for all individuals, especially when it comes to fat stored within muscles. Lead researcher Viviany Taqueti, director at Brigham and Women’s Hospital, explained that BMI, despite its widespread use, can be a flawed marker of cardiovascular risk.
“Obesity is now one of the biggest global threats to cardiovascular health,” Taqueti said. “Yet BMI remains a controversial and often inadequate measure of cardiovascular prognosis, especially for women, where high BMI may reflect ‘benign’ types of fat.”
Fat stored within muscles, known as intermuscular fat, can be found throughout the body, but its prevalence varies significantly from person to person. Unlike subcutaneous fat, which is stored beneath the skin, muscle fat can contribute to inflammation and disrupt glucose metabolism, potentially leading to insulin resistance and metabolic syndrome. These changes in metabolism can, in turn, cause damage to blood vessels, including those that supply the heart.
The study’s authors argue that existing obesity metrics fail to account for the risks posed by muscle fat. They emphasized the importance of a new measure, the “fatty muscle fraction,” which quantifies the ratio of intermuscular fat to total muscle plus fat. To assess this, researchers used advanced imaging techniques such as Positron Emission Tomography (PET) and CT scans to measure body composition and evaluate the heart’s function. Over six years of follow-up, the results indicated that the presence of excessive muscle fat significantly correlated with cardiovascular dysfunction.
“While increased intermuscular fat is associated with coronary microvascular dysfunction and poor cardiovascular outcomes, it occurs independently of BMI and other conventional risk factors,” the researchers wrote.
However, despite these compelling findings, Taqueti noted that much remains unknown. The study has not yet determined how to reduce the risks associated with fatty muscle tissue, and it is unclear how interventions like weight-loss therapies might affect muscle fat compared to fat stored elsewhere in the body.
The research opens a new chapter in understanding the connection between muscle fat and heart health, urging further investigation into potential treatment options and alternative risk assessments for cardiovascular diseases.
As the medical community continues to uncover the complexities of obesity and heart disease, these findings underscore the importance of looking beyond traditional measures like BMI and focusing on a more nuanced understanding of fat distribution within the body.
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