Hidden fat quietly damages arteries, even in people who look healthy
A new study led by researchers at McMaster University reveals that hidden fat deep inside the abdomen and liver may quietly damage arteries, even in people who appear healthy. Published in Communications Medicine, the research challenges the conventional reliance on body-mass index (BMI) as the sole measure of obesity and risk, offering fresh insight into how “skinny fat”—the presence of visceral and hepatic fat despite a normal weight—can influence cardiovascular health.
Visceral fat, the fat that wraps around internal organs, and hepatic fat, stored in the liver, are already known to increase the risk of type 2 diabetes, high blood pressure, and heart disease. But until now, their impact on artery health and stroke risk was less clear. This study sheds new light on how these hidden fats relate to artery integrity, independent of traditional risk factors.
How the study linked hidden fat to carotid artery changes
Using advanced MRI imaging and data from more than 33,000 adults in Canada and the United Kingdom, researchers found robust associations between visceral and liver fat and changes in the carotid arteries in the neck. These arteries supply blood to the brain, and their narrowing or blockage is a well-established predictor of stroke and heart attack.
“This study shows that even after accounting for traditional cardiovascular risk factors like cholesterol and blood pressure, visceral and liver fat still contribute to artery damage,” said Russell de Souza, co-lead author and associate professor at McMaster. He emphasized that these findings point to a new dimension of cardiovascular risk that may remain hidden if clinicians only measure weight or BMI.
What the findings mean for patients and clinicians
The researchers distinguished the effects of visceral fat from those of hepatic fat. Visceral fat was consistently associated with carotid plaque buildup and arterial wall thickening, while liver fat showed a weaker but still meaningful link. Importantly, the associations persisted even after adjusting for lifestyle factors and other metabolic risks, suggesting a direct role for these fat depots in arterial health.
For clinicians, the study underscores the need to move beyond BMI and waist circumference when assessing cardiovascular risk. Imaging-based assessments that reveal fat distribution could become important tools in identifying individuals at higher risk who might otherwise be missed by traditional screens.
Implications for public health and everyday life
The findings carry important implications for middle-aged adults and those who feel healthy despite carrying extra weight around the abdomen. The notion of “skinny fat” helps explain why some people with a normal BMI still face elevated cardiovascular risk. Fat stored deep inside the body is metabolically active, linked to inflammation, and can contribute to artery damage even in the absence of overt obesity.
As Sonia Anand, the study’s corresponding author and a vascular medicine specialist at Hamilton Health Sciences, explains: “You can’t always tell by looking at someone whether they have visceral or liver fat. This kind of fat is metabolically active and dangerous; it’s linked to inflammation and artery damage even in people who aren’t visibly overweight. That’s why it’s so important to rethink how we assess obesity and cardiovascular risk.”
Looking ahead: redefining obesity assessments
The research team analyzed two major cohorts—the Canadian Alliance for Healthy Hearts and Minds (CAHHM) and the UK Biobank—using MRI scans to measure fat distribution and artery health. The results invite a broader conversation about how healthcare systems screen for cardiovascular risk, potentially incorporating imaging or biomarker approaches that capture hidden fat deposition.
In the broader fight against heart disease, these findings reinforce a simple but powerful message: staying lean on the outside does not necessarily guarantee minimal cardiovascular risk. Clinicians and patients alike should consider hidden fat as a meaningful factor in arteries’ health and stroke risk—and take proactive steps to address it through targeted lifestyle changes and, when appropriate, imaging assessments.
