You can’t always tell by looking at someone whether they’re carrying harmful fat. A new study from McMaster University finds that fat hidden deep inside the body, around internal organs and in the liver, may quietly damage arteries, even in people who appear healthy.
Published in Communications Medicine, the research challenges the long-standing use of body mass index (BMI) as a marker of health and adds to growing evidence that where fat is stored matters more than how much you weigh.
Using advanced MRI imaging and data from more than 33,000 adults in Canada and the United Kingdom, researchers found that higher levels of visceral fat (the kind that wraps around internal organs) and liver fat were linked to thickening and narrowing of the carotid arteries, the blood vessels in the neck that supply the brain. Such changes are early signs of atherosclerosis, a major risk factor for heart attack and stroke.
“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, PhD, associate professor of health research methods, evidence, and impact at McMaster. “The findings are a wake-up call for clinicians and the public alike.”
Researchers found that people with higher visceral fat had a stronger link to artery damage than those with excess liver fat, though both types were associated with poorer artery health. The effects remained even after adjusting for lifestyle and metabolic factors such as diet, smoking and diabetes.
“You can’t always tell by looking at someone whether they have visceral or liver fat,” said Sonia Anand, MD, senior author of the study and a vascular medicine specialist at Hamilton Health Sciences. “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.”
The researchers say these findings underscore the need to look beyond BMI when assessing heart health. While most people won’t need an MRI scan, maintaining healthy habits, such as eating a balanced diet rich in whole foods, being physically active and limiting added sugars and alcohol, can help reduce visceral and liver fat over time.
The study analyzed data from two large health projects: the Canadian Alliance for Healthy Hearts and Minds (CAHHM) and the UK Biobank. The work was led by de Souza and Marie Pigeyre, MD, of McMaster’s Department of Medicine.
This research was supported by the Canadian Partnership Against Cancer, the Heart and Stroke Foundation of Canada, and the Canadian Institutes of Health Research, with additional contributions from the Population Health Research Institute, the Montreal Heart Institute, Sunnybrook Health Sciences Centre and others. MRI reading costs were supported in-kind by Sunnybrook Hospital and Bayer AG provided IV contrast.