The prevailing understanding of heart attack risk often centers around body mass index (BMI) as a key indicator. However, groundbreaking research from Harvard Medical School challenges this conventional wisdom, revealing that individuals considered slim based on their BMI might still be at significant risk due to the presence of hidden pockets of fat within their muscles, termed “intramuscular fat.” This type of fat, analogous to the marbling in beef that enhances its flavor and tenderness, can have detrimental health consequences in humans. The study demonstrated a strong correlation between higher levels of intramuscular fat and an increased risk of heart attack and heart failure, independent of BMI. In contrast, higher amounts of lean muscle mass were associated with a reduced risk. This finding underscores the limitations of using BMI as a sole predictor of heart health and highlights the importance of considering body composition, particularly the distribution of fat and muscle.
The Harvard scientists’ analysis involved 669 individuals who presented with symptoms suggestive of heart problems, such as chest pain and shortness of breath, but were found to be free of obstructive coronary artery disease. Through sophisticated imaging techniques, the researchers meticulously assessed heart function and analyzed body composition, including the precise location and quantity of fat and muscle within the torso. The study meticulously differentiated between fat stored within muscles (intramuscular fat) and fat stored beneath the skin (subcutaneous fat), and strikingly, only intramuscular fat emerged as a significant risk factor for heart-related complications.
The researchers discovered that for every 1% increase in intramuscular fat, the risk of coronary microvascular dysfunction (CMD), a condition affecting the small blood vessels in the heart, increased by 2%, while the risk of severe heart disease rose by a concerning 7%. This association points to a potential mechanism where intramuscular fat, unlike subcutaneous fat, contributes to inflammation and insulin resistance, consequently impacting blood vessels and the heart muscle. The findings suggest that targeting interventions that specifically reduce intramuscular fat might be crucial for mitigating heart disease risk, especially for individuals who might appear healthy based on BMI alone.
This novel research underscores the limitations of relying solely on BMI as a measure of cardiovascular health. Prof. Viviany Taqueti, the study’s lead researcher, emphasizes that BMI often fails to capture the nuances of body composition, particularly in women where a high BMI may reflect more benign forms of fat. The study’s findings are particularly pertinent to ongoing research investigating the impact of weight-loss drugs on heart health. There is a concern that some of these medications might inadvertently lead to a loss of lean muscle mass, potentially exacerbating the negative effects of intramuscular fat.
While the study convincingly establishes the link between intramuscular fat and heart disease risk, further research is needed to understand how to effectively reduce this specific type of fat. Currently, the optimal strategies for targeting intramuscular fat, including the role of lifestyle interventions and pharmacological approaches, remain unclear. The study paves the way for future investigations to explore novel therapeutic targets and personalized interventions that address the distinct challenges posed by intramuscular fat accumulation.
This discovery holds significant implications for public health and clinical practice. It calls for a shift in focus from solely relying on BMI to incorporating more comprehensive assessments of body composition, including the distribution of fat and muscle, in evaluating cardiovascular risk. Developing targeted interventions that specifically address intramuscular fat could revolutionize preventive strategies and treatment approaches for heart disease, potentially saving lives and improving overall health outcomes. The ongoing quest to understand the complex interplay between body composition and heart health continues, promising to refine our approach to cardiovascular disease prevention and management.
