Imagine two people with the same BMI — the number doctors use to check if your weight is healthy. One carries extra fat around their belly, while the other stores it elsewhere. According to new research, the first person might be at much greater risk for heart disease, even if they look equally healthy on the scale.
Scientists at the University of Glasgow found that measuring waist size alongside BMI can catch heart disease risks that BMI alone would miss. Lead researcher Estefania Fuentes Avalos presented the findings at the International Congress on Obesity in Mexico City in July.
The study tracked 382,769 white adults in the UK Biobank project, ages 40 to 69, for 12 years. None had heart disease when the study began. Using a new framework from The Lancet Diabetes & Endocrinology Commission, the researchers combined BMI with waist measurements — instead of relying on BMI alone — to determine who had excess body fat.
The results were striking. About 74 percent of participants had excess body fat under the new framework. Among them, 102,237 people had what researchers called preclinical obesity — excess body fat without other health problems like high blood pressure or joint pain yet. Another 182,953 had clinical obesity, meaning they had both excess body fat and obesity-related conditions.
Over the 12-year follow-up, 41,742 participants developed cardiovascular disease and 8,832 died from it. The gaps between groups were dramatic. Women with clinical obesity developed heart disease at 2.5 times the rate of women without obesity, and died from it at nearly three times the rate. Men with clinical obesity faced roughly double the risk of developing heart disease and 2.6 times the risk of dying from it.
The danger comes from visceral fat — the kind that pools around the belly. Unlike fat stored in other places, this fat is metabolically active, meaning it releases inflammatory substances into the bloodstream. Over time, that chronic inflammation can damage blood vessels and speed up plaque buildup in arteries.
The researchers argue that this new approach gives doctors a window to intervene early, before conditions like high blood pressure develop. "Detecting cardiovascular risk at an early stage is essential," Fuentes Avalos said, "particularly at the preclinical stage of obesity, as it provides a window of opportunity to implement timely, targeted interventions."
In 2021, an estimated 1.9 million cardiovascular deaths worldwide were linked to high BMI — almost one in ten heart-related deaths globally. The researchers believe using waist measurements alongside BMI could help prevent hundreds of thousands of those deaths by catching risk earlier.