Obese people who don't have certain signs of heart disease now may still be at higher risk for future disease than normal-weight people, according to a new study.
Researchers looked at nearly 15,000 adults in Korea, ages 30 to 59, who had no heart disease and were all metabolically healthy, meaning they had normal blood pressure, cholesterol and blood sugar levels, which are important factors in heart health.
Using heart scans, the researchers found that the obese people were still more likely to have early plaque buildup in their arteries compared to their normal-weight counterparts.
The level of a person's plaque buildup has been linked to their risk of future heart disease, the researchers said.
The findings cast doubt on the idea that people can be obese but still healthy, the researchers said. [Beyond Vegetables and Exercise: 5 Ways to be Heart Healthy]
"Obese individuals who are considered 'healthy' because they don't currently have heart disease risk factors should not be assumed healthy by their doctors," said study researcher Dr. Yoosoo Chang, a professor at Sungkyunkwan University, School of Medicine in Seoul.
The idea of "healthy" obesity is controversial – studies have reached mixed results when comparing the risk of heart problems in metabolically healthy obese people with that of metabolically healthy people of normal weight.
But most previous studies looked at obese and normal-weight people over time, to see how many people in each group developed heart disease or suffered a heart attack.
In contrast, the researchers of the new study used CT scans of apparently healthy people to look for the plaque buildup in the blood vessels that occurs before it reaches a level that causes a clinical problem.
Measuring calcium levels in the plaques on the artery walls, researchers found that despite their normal cholesterol levels, obese people scored significantly higher on coronary artery calcium, which is a test for coronary artery disease (atherosclerosis).
The study shows "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," Chang said. "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."
The new findings are in line with those of a recent review of 12 studies that included more than 60,000 people followed for at least 10 years. In that review, which was published in December, researchers found that "healthy" obese people had 24 percent higher risk for heart problems, including heart attack and stroke, compared with normal-weight people.
These recent findings that suggest obese people with no apparent heart disease may not be healthy "highlight the fact that obesity per se is a genuine disease," said Rishi Puri, medical director of Cleveland Clinic Atherosclerosis Imaging Core Laboratory.
"It also seriously questions the fundamental concept of the need to define a subset of obese individuals as 'metabolically healthy,'" Puri wrote in an editorial accompanying the study.
Researchers noted in the study that higher rates of early plague buildup in obese people tend to occur in those who had blood pressure, cholesterol and sugar levels closer to "unhealthy" thresholds. In other words, some of the obese people in the study were considered healthy because of the cut-off levels used in the definition of metabolic health.
The study is published today (April 30) in the Journal of the American College of Cardiology.