Hidden fat in muscles – similar to beef marbling – leads to a higher risk of dying from heart attacks or heart failure regardless of body weight, according to a study.
While ‘fatty marbling’, or flecks of fat running through meat, is commercially valued in livestock, little is known about this type of body fat in humans and its impact on health.
Now, experts have found that it could be linked to inflammation and insulin resistance which can cause damage to blood vessels around the heart.
And the new findings add evidence that simply measuring BMI or waist circumference are not enough to assess the risk of heart health issues, researchers warned.
A team from Brigham and Woman’s Hospital in Boston analysed data on 669 people being evaluated for chest pain or shortness of breath.
The group were given scans to assess their heart function and researchers also used CT scans to analyse body composition, measuring the amounts and location of fat and muscle in sections of their torso.
To determine the amount of fat stored in muscles, the team calculated the ratio of intermuscular fat to total muscle plus fat using a measurement they called the fatty muscle fraction.
Patients were followed up for around six years and the scientists recorded whether any died or were hospitalised for a heart attack or heart failure.
Their findings revealed that people with higher amounts of fat stores in their muscles were more likely to have damage to the tiny blood vessels that serve the heart, and they were more likely to go on to die or be hospitalised for heart disease.
For every 1 per cent increase in the ratio of fatty muscle fraction, there was a 2 per cent increase in the risk of damage to the heart’s small blood vessels and a 7 per cent increased risk of developing serious heart disease.
This was regardless of BMI, they found.
Professor Vivianay Taqueti, lead author of the study, said fat stores in the muscles may be contributing to inflammation and insulin resistance.
‘In turn, these chronic insults can cause damage to blood vessels, including those that supply the heart, and the heart muscle itself,’ she added.
‘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.’
Professor Taqueti said it is not yet known how to lower the risk for people with fatty muscles.
‘For example, we don’t know how treatments such as new weight-loss therapies affect fat in the muscles relative to fat elsewhere in the body, lean tissue, and ultimately the heart,’ she said.
‘Obesity is now one of the biggest global threats to cardiovascular health, yet body mass index – our main metric for defining obesity and thresholds for intervention – remains a controversial and flawed marker of cardiovascular prognosis.
‘This is especially true in women, where high body mass index may reflect more ‘benign’ types of fat.’
