Being overweight has long been linked to heart conditions and type 2 diabetes, but even people who look thinner could be at risk, researchers suggest.
A new study led by researchers at McMaster University in Ontario, Canada, explains there is such a thing as being “skinny-fat” – someone who appears to be healthy and slim but in fact has hidden fat deep inside their organs.
The findings, published in Communications Medicine, suggest the fat hidden in the abdomen and liver may quietly damage arteries.
It challenges the long-standing reliance on body-mass index (BMI) as a measure of obesity and offers fresh insight into how hidden fat contributes to heart disease.
Visceral fat, which wraps around internal organs, and hepatic fat stored in the liver are known to increase the risk of type 2 diabetes, high blood pressure, and heart disease – but their effects on artery health are less known.
“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 co-lead author Russell de Souza.
“The findings are a wake-up call for clinicians and the public alike.”
Excess weight can lead to fatty material building up in the arteries. If the arteries that carry blood to the heart get blocked, this can lead to a heart attack.
But it’s not just the fat under the skin that can cause problems – fat that sits around the organs also affects the way the heart and blood vessels function.
Researchers used MRI imaging and data from over 33,000 adults in the UK and Canada and found that visceral and hepatic fat are strongly linked to the thickening and clogging of carotid arteries in the neck. These arteries supply blood to the brain, and their narrowing is a key predictor of stroke and heart attack.
Importantly, these associations held even after the researchers adjusted for lifestyle and metabolic risk factors.
“You can’t always tell by looking at someone whether they have visceral or liver fat,” said vascular medicine specialist Sonia Anand, corresponding author of the study.
“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.”
Researchers suggest that because this fat is not visible and cannot be measured with BMI or waist circumference, doctors should consider using imaging-based assessments of fat distribution.
Alex Miras, professor of endocrinology at Ulster University, told The Independent: “Visceral adiposity can cause coronary artery disease even in people with a normal or near-normal BMI. This is more common in specific ethnic groups like south Asians.”
Although this fat is not visible from the outside, it can still be tackled the same way as people who are overweight – through diet and exercise or medication.
He added: “Any form of weight loss, through behavioural interventions or obesity pharmacotherapy, is likely to have a positive effect in reducing cardiovascular disease. They also need to have their cholesterol and blood pressure aggressively treated.”
