A trending idea known as “healthy obesity,” which implies it’s possible to be obese and also healthy, has made headlines in recent years. Some studies have found that overweight people didn’t necessarily have a greater chance of developing heart disease or cancer than people at normal weight — as long as they were metabolically fit.

But a new study, published in the Journal of the American College of Cardiology, challenges this idea. Researchers state that obese people — even if they don’t have signs of cardiovascular disease — have a much higher prevalence of early plaque buildup in arteries that people of normal weight do. In the study, authors labelled people “obese” if they had a BMI of over 25, and examined over 14,000 metabolically healthy people. They found that obese people had a higher chance of developing subclinical coronary atherosclerosis, or early-stage plaque buildup in the arteries. This type of plaque buildup can lead to heart attacks if not treated properly.

“Obese individuals who are considered ‘healthy’ because they don’t currently have heart disease risk factors, should not be assumed healthy by their doctors,” Dr. Yoosoo Chang, lead author of the study and professor at Kangbuk Samsung Hospital Total Healthcare Center for Cohort Studies, said in a press release. “Our research shows that the presence of obesity is enough to increase a person’s risk of future heart disease and that the disease may already be starting to form in their body. It’s important that these people learn this while they still have time to change their diet and exercise habits to prevent a future cardiovascular event.”

Previously, researchers worked to prove that it was possible to be a “metabolically healthy” obese person, who didn’t have diabetes or heart disease, and who maintained good cholesterol and blood pressure. While it may be possible, it doesn’t mean that it’s acceptable to maintain an overweight lifestyle. And you can see it from the other direction too; just because you’re thin, doesn’t mean you’re healthy, either.

Dr. Rishi Puri of the Cleveland Clinic’s Atherosclerosis Imaging Core Lab believes that obesity is essentially a disease, and that this research overturns the “healthy obesity” idea that has just grown popular in the past few years. “Given our current lack of a ‘cure’ or efficient means of successfully treating obesity over the longer term, might the resources spent on trying to define and justify the existence of a ‘metabolically healthy’ obese population be more wisely allocated to elucidating ways to prevent or treat obesity?” Puri writes in a corresponding editorial.

But perhaps it’s more about focusing on health rather than weight, and perhaps doing the things that make us healthy will in turn lead to normal weight. “The things we recommend for people to be fit are the very things we are recommending for people to not be fat,” Dr. David Katz of the Yale University Prevention Research Center told TIME. So don’t use healthy obesity as an excuse to stay overweight; and for all the thin people out there living unhealthy lifestyles in other ways, be aware that your weight isn't the only marker of good health.