After analyzing MRI scans and health data from more than 33,000 people in Canada and the United Kingdom, researchers at McMaster University in Canada found that visceral fat, which accumulates deep within the body and around internal organs, is closely linked to damage to the carotid arteries that supply blood to the brain, increasing the risk of stroke and heart disease.
The team explained that these results call into question the reliance on the body mass index (BMI) as the primary measure of obesity, as internal fat can be harmful even when weight appears normal.
"Our results show that even after taking into account traditional risk factors such as cholesterol and blood pressure, visceral and liver fat remain direct causes of arterial damage," said study co-author Professor Russell de Souza, from McMaster University's Department of Health Research Methods.
De Souza described the results as "a wake-up call for doctors and the public alike."
For her part, Professor Marie Beguiere emphasized that the study highlights the need for more accurate methods for assessing body fat distribution, not relying solely on weight or waist size.
"You can't always tell whether someone has visceral or hepatic fat just by looking at them," added Professor Sonia Anand, a vascular specialist at Hamilton Hospitals in Canada. "This fat is metabolically active and dangerous because it is associated with inflammation and arterial damage, even in those who are not visibly obese."
The researchers noted that modern medical imaging techniques could help detect these "hidden" fats, enabling early prevention of cardiovascular disease.
These findings coincide with growing calls to revisit the global definition of obesity. Fifty-eight international experts recently proposed amending the established body mass index system, arguing that it does not accurately reflect the distribution of body fat and does not differentiate between superficial fat and dangerous deep fat.
Experts suggest adopting additional measures such as waist circumference and height-to-weight ratio to provide a more realistic picture of body condition. Studies from Harvard University and Massachusetts General Hospital indicate that applying this new definition could increase the number of people classified as obese by up to 60%.
The study was published in the journal Communications Medicine.
