NEW DELHI — People with pockets of fat hidden inside their muscles are at a higher risk of dying or being hospitalised from a heart attack or heart failure, regardless of their body mass index, according to research on Monday.
The new study, published in the European Heart Journal, adds evidence that existing measures, such as body mass index (BMI) or waist circumference, are not adequate to evaluate the risk of heart disease accurately for all people.
The study showed that people with higher amounts of fat stored in their muscles were more likely to have damage to the tiny blood vessels that serve the heart (coronary microvascular dysfunction or CMD). They were also more likely to die or be hospitalised for heart disease.
People who had high levels of intermuscular fat and evidence of CMD were at an especially high risk of death, heart attack, and heart failure. "Knowing that intermuscular fat raises the risk of heart disease gives us another way to identify people who are at high risk, regardless of their body mass index.
These findings could be particularly important for understanding the heart health effects of fat and muscle-modifying incretin-based therapies, including the new class of glucagon-like peptide-1 receptor agonists,” said Professor Viviany Taqueti, Director of the Cardiac Stress Laboratory at Brigham and Women's Hospital, US.
The study analysed muscle and different types of fat in 669 people to understand how body composition can influence the small blood vessels or 'microcirculation' of the heart, as well as the future risk of heart failure, heart attack, and death.
These were followed up for around six years. Besides checking how well their hearts were functioning, the team also used CT scans to analyse each patient's body composition, measuring the amounts and location of fat and muscle in a section of their torso.
Further, the team calculated the ratio of intermuscular fat to total muscle plus fat -- a measurement they called the fatty muscle fraction. For every 1 per cent increase in fatty muscle fraction, there was a 2 per cent increase in the risk of CMD and a 7 per cent increased risk of future serious heart disease, regardless of other known risk factors and body mass index.
On the other hand, people with higher amounts of lean muscle had a lower risk. Fat stored under the skin (subcutaneous fat) did not increase the risk.
"Compared to subcutaneous fat, fat stored in muscles may be contributing to inflammation and altered glucose metabolism, leading to insulin resistance and metabolic syndrome.
In turn, these chronic insults can cause damage to blood vessels, including those that supply the heart, and the heart muscle itself,” Professor Taqueti said.
The team is assessing the impact of treatment strategies including exercise, nutrition, weight-loss drugs, or surgery, on body composition and metabolic heart disease, to help lower the risk for people with fatty muscles.