Researchers at McMaster University have discovered that visceral fat around organs and fat in the liver can silently harm arteries, increasing stroke and heart attack risks, regardless of outward appearance. The study, involving MRI scans of over 33,000 adults, challenges the reliability of BMI for assessing cardiovascular health. Published on October 17, 2025, the findings urge a shift toward imaging-based evaluations.
A new study from McMaster University reveals that fat stored deep in the abdomen and liver poses a significant threat to artery health, even among individuals who appear fit. Led by scientists including Russell de Souza and Marie Pigeyre, the research analyzed MRI data from more than 33,000 adults across Canada and the United Kingdom, drawn from the Canadian Alliance for Healthy Hearts and Minds (CAHHM) and UK Biobank cohorts.
The investigation, published on October 17, 2025, in Communications Medicine, found strong links between higher levels of visceral fat—surrounding internal organs—and thickening or clogging of the carotid arteries, which supply blood to the brain. Liver fat showed a smaller but notable association with these changes. These effects persisted even after adjusting for factors like cholesterol, blood pressure, diet, exercise, and other metabolic risks.
"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 in McMaster's Department of Health Research Methods, Evidence, and Impact.
The results question the long-held reliance on body-mass index (BMI) to gauge obesity and heart disease risk, as hidden fats can drive inflammation and plaque buildup without visible signs. "You can't always tell by looking at someone whether they have visceral or liver fat," noted Sonia Anand, corresponding author and professor in McMaster's Department of Medicine. "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."
Clinicians may need to adopt advanced imaging to better assess cardiovascular threats, particularly for midlife adults. The study received support from organizations including the Heart and Stroke Foundation of Canada and the Canadian Institutes of Health Research.