(CNN) The idea that you can be overweight or obese yet healthy -- if factors such as your blood sugar, blood pressure or cholesterol levels are normal -- is a myth, according to a new study, and messaging around this should be changed.

Carrying those extra pounds can increase risk of coronary heart disease by up to 28% even if your other results appear normal, further disproving the notion that people can be "fat but fit."

"We conclude that there is no such thing as being healthy obese," said Camille Lassale, an epidemiologist from Imperial College London's School of Public Health, now based at University College London, who led the research. "You are at an increased risk of heart disease."

But more recent studies have gone against this belief, showing that people with excess weight still have a greater chance of developing heart disease than those with a normal weight.

The latest study, published Monday in the European Heart Journal , confirms that stance.

Proving that risk increases with excess body mass

Lassale's team conducted the largest study to date investigating the impact on heart health when people are overweight or obese, as well as when they are "metabolically unhealthy," such as having elevated blood pressure, blood sugar, triglycerides (which store fat in your body) and waist size or having reduced levels of HDL cholesterol, the "good" form, which the body needs.

These factors combine to cause metabolic syndrome, which increases risk of various heart-related conditions, including heart disease and stroke.

The team used data from more than 7,600 adults who experienced coronary heart disease -- when coronary arteries are blocked and can cause a heart attack -- and categorized them by their body mass index as well as by their metabolic health, such as high blood sugar levels. They also used data from 10,000 healthy controls to represent the general health of the population being sampled.

People were sampled from the larger European Prospective Investigation into Cancer and Nutrition, which contains data from more than half a million people across 10 European countries. People within the samples were first separated into two groups, healthy and unhealthy, based on whether they had three or more of the markers for being "metabolically unhealthy," followed by separation by BMI to class them as normal weight, overweight or obese.

BMI is the ratio between weight and height, with a BMI of 25 to 29.9 considered overweight and over 30 being obese.

Those in the metabolically unhealthy group were at greater risk for coronary heart disease, with unhealthy obese people having the highest risk.

But the researchers then looked within the group classified as "metabolically healthy" -- without risk factors such as high blood sugar. They found that within this seemingly healthy group, people who were overweight or obese had a greater risk of heart disease than normal weight people: 26% increased risk in those who were overweight and 28% increased risk in those who were obese.

"Even if you are classified as metabolically healthy, (excess weight) was associated with an increased risk of heart disease," Lassale said. "It's another brick in the wall of evidence that being healthy overweight is not true."

The risk is much higher in the unhealthy group, Lassale added, but she highlighted the need for those without signs such as high blood pressure not to rest on their laurels. "(They) seem to be at an intermediate risk," she said. "We saw that they went on to develop (more) heart attacks."

But the team members acknowledge that they cannot say with certainty why those carrying extra weight went on to have more heart disease.

Healthy now, unhealthy later

The larger European study from which these data were obtained collected only information such as BMI, blood pressure and blood sugar at the start of the study. For the 12 years after those data were collected, people were followed up only to identify whether they had experienced aspects of coronary heart disease, such as a heart attack.

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"We couldn't monitor the evolution of their metabolic health," Lassale said. "They probably went on to be metabolically unhealthy."

What she does know, however, is that this further emphasizes the need to prevent the burgeoning obesity epidemic.

"This reinforces the fact that obesity in itself is a risk factor," Lassale said. "Every effort should be made by health professionals to advise on lifestyle changes regardless of these metabolic factors." These factors are likely to become abnormal if weight is not controlled, she added.

"This study provides robust evidence that there is no such thing as 'healthy obesity,' " said Metin Avkiran, associate medical director at the British Heart Foundation, who was not involved in the study. "The take-home message here is that maintaining a healthy body weight is a key step towards maintaining a healthy heart."

Nick Finer, honorary clinical professor at the National Centre for Cardiovascular Prevention and Outcomes at University College London who also was not involved in the study, added that it "supports the ever-pressing need for governments, local authorities, public health bodies and individuals to seriously address the issues leading to our current levels of overweight and obesity."