Hidden fat may quietly damage arteries, beyond what BMI reveals
A groundbreaking study led by researchers at McMaster University shows that hidden fat deep inside the abdomen and in the liver can quietly damage arteries—even in people who appear healthy by traditional measures. Published in Communications Medicine on October 17, 2025, the research challenges the long-standing reliance on body-mass index (BMI) as a sole metric of obesity and cardiovascular risk.
The study brings attention to two forms of fat: visceral fat, which surrounds internal organs in the abdomen, and hepatic fat, stored in the liver. While both have been linked to higher risks of Type 2 diabetes, high blood pressure, and heart disease, their specific impact on artery health has been less clear. This new work connects hidden fat to negative changes in the carotid arteries, the major vessels in the neck that supply blood to the brain.
Using advanced magnetic resonance imaging (MRI) and data from more than 33,000 adults across Canada and the United Kingdom, the researchers assessed fat distribution and artery health with unprecedented detail. They found that visceral fat was consistently associated with carotid plaque buildup and thickening of the artery walls, while liver fat showed a weaker but still meaningful association. Importantly, these relationships persisted even after accounting for traditional risk factors such as cholesterol levels and blood pressure, suggesting that hidden fat contributes to artery damage beyond conventional metrics.
“These findings are a wake-up call for clinicians and the public alike,” said Russell de Souza, co-lead author and associate professor at McMaster University. “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.”
The research team drew data from two major cohorts—Canada’s CAHHM (Canadian Alliance for Healthy Hearts and Minds) and the UK Biobank—using MRI scans to quantify fat distribution and examine carotid artery health. The study also measured how fat distribution related to plaque formation and arterial wall thickening, both of which are key predictors of stroke and heart attack.
From a clinical perspective, the study calls for a shift beyondBMI and waist measurements toward imaging-based assessments of fat distribution in at-risk patients. For middle-aged adults, hidden fat may be a silent driver of vascular disease, underscoring the need for more nuanced screening strategies in routine care.
“You can’t always tell by looking at someone whether they have visceral or liver fat,” noted Sonia Anand, corresponding author and vascular medicine specialist at Hamilton Health Sciences. “This fat is metabolically active and dangerous; it fuels inflammation and artery damage even when someone seems to be at a healthy weight. It’s time to rethink how we assess obesity and cardiovascular risk.”
The study’s impact extends beyond individual diagnosis. It suggests that clinicians incorporate imaging-based fat assessments into risk stratification, particularly for patients who do not fit the typical high-BMI profile but may harbor dangerous fat deposits.
Funding and collaboration supported the work, including the Canadian Partnership Against Cancer, the Heart and Stroke Foundation of Canada, and the Canadian Institutes of Health Research. MRI reading costs were provided in-kind by Sunnybrook Hospital, and materials from Bayer AG supported certain imaging components. The research also leveraged data from initiatives such as the Population Health Research Institute and the PURE Study, illustrating the power of large, harmonized datasets in uncovering hidden health risks.
What this means for individuals and clinicians
For individuals, the study is a reminder that looking healthy on the outside does not guarantee low cardiovascular risk. Maintaining metabolic health through balanced diet, regular physical activity, and monitoring of metabolic markers remains crucial, but awareness that hidden fat can contribute to arterial damage prompts earlier and more targeted screening for those at risk.
For clinicians, the message is clear: consider imaging-based assessments of fat distribution alongside traditional risk factors. As research evolves, these tools could help identify patients who would benefit most from early intervention to protect artery health and reduce the risk of stroke and heart attack.