Hidden fat and the quiet risk to artery health
Obesity is often evaluated using body-mass index (BMI) and outward signs of excess weight. A new study led by researchers at McMaster University reframes that view by focusing on hidden fats—the visceral fat that wraps around internal organs and the fat stored in the liver. Using advanced MRI imaging on more than 33,000 adults from Canada and the United Kingdom, the researchers found that these concealed fat depots can quietly damage arteries, independent of traditional risk factors.
What the study looked at and what it found
The international study, published in Communications Medicine, examined how visceral fat and hepatic fat relate to the health of carotid arteries in the neck. Carotid arteries supply blood to the brain, and their narrowing or plaque buildup is a known predictor of stroke and heart attack. The team analyzed data from two large cohorts—the Canadian Alliance for Healthy Hearts and Minds (CAHHM) and the UK Biobank—measuring fat distribution with MRI and assessing arterial health through imaging markers.
Key findings include a strong link between visceral fat and carotid plaque formation as well as thickening of artery walls. Liver fat also showed a significant, though somewhat weaker, association with arterial changes. Crucially, these associations persisted even after accounting for lifestyle factors and conventional metabolic risks such as cholesterol and blood pressure. In other words, hidden fat can contribute to artery damage beyond what doctors typically monitor.
Why this changes clinical practice
Historically, clinicians have relied on BMI, waist circumference, and basic metabolic indicators to gauge cardiovascular risk. This study adds a new dimension by showing that someone can appear healthy by conventional metrics yet harbor fat that quietly harms arteries. The researchers emphasize that the metabolic activity of visceral and liver fat—not just their presence—drives inflammation and vascular injury. This reframes risk assessment: imaging-based approaches that quantify fat distribution may be necessary to accurately identify individuals at higher risk for stroke or heart disease.
Leading author Russell de Souza, an associate professor at McMaster, notes that “even after adjusting for traditional cardiovascular risk factors, visceral and liver fat still contribute to artery damage.” Co-lead Marie Pigeyre and the team suggest that the medical community should broaden obesity evaluation beyond BMI to include more nuanced measurements of fat distribution when appropriate and feasible.
What this means for patients and public health
The findings carry important implications for middle-aged adults and older individuals who may not look overweight but carry medically significant fat deep inside their abdomen and liver. For clinicians, this means considering targeted imaging or other assessments of fat distribution when assessing cardiovascular risk. For the public, it underscores a broader message: healthy appearance does not guarantee protected arteries, and hidden fat can pose a real danger even in people who are not visibly overweight.
As the authors point out, visceral fat is metabolically active and linked to inflammation, which can hasten arterial damage. Liver fat follows a similar path, contributing to a cascade of metabolic disturbances that ultimately affect cardiovascular health. The study’s authors stress that the findings are a wake-up call for both clinicians and patients to rethink obesity and heart-disease risk in a more nuanced way.
Looking ahead
Future research will likely explore how to efficiently screen for visceral and hepatic fat in routine practice and whether interventions that reduce hidden fat translate into measurable improvements in artery health. In the meantime, lifestyle strategies that limit visceral and liver fat—such as balanced diets, physical activity, and managing metabolic risk factors—may offer tangible benefits for arterial integrity and overall cardiovascular risk reduction.
Key takeaways
- Hidden visceral and liver fat are linked to arterial damage beyond BMI measurements.
- Imaging-based assessment may improve cardiovascular risk prediction.
- Healthy-looking individuals can still harbor fat that harms arteries.
