Can you be fit but fat? Over the past 15 years, scientists have been trying to figure out if “healthy obesity” is the real deal and in the latest research, Swedish doctors say it’s a myth.

Karolinska Institutet scientists say that the white fat tissue samples from those classified as obese have abnormal changes in gene expression and how they respond to producing insulin. It doesn’t matter if you’re considered a healthy obese or simply overweight.

“The findings suggest that vigorous health interventions may be necessary for all obese individuals, even those previously considered to be metabolically healthy,” Dr. Mikael Ryden, the study’s first author, said in a statement.

“Since obesity is the major driver altering gene expression in fat tissue, we should continue to focus on preventing obesity,” he said.

READ MORE: New research debunks controversial ‘healthy obesity’ theory

One in four Canadian adults is clinically obese, according to the Canadian Obesity Network. It’s a risk factor for heart disease, diabetes and cancer, among other conditions.

Story continues below advertisement

The idea behind “healthy obesity” is that you can have excess body fat, while still being healthy.

Since the 1940s, the medical community has been studying the link between being overweight and heart disease risk. Decades later though, in the early 2000s, doctors found that some people grappling with obesity were “relatively healthy.”

“One conclusion researchers have drawn from this is as long as you are fit, it may not matter whether you are overweight or obese. However, there is some convincing research suggesting that so-called healthy obesity is a transient state and obesity may lead to long-term health consequences even if a person is otherwise healthy and fit…,” Dr. Andrew Stokes, a Boston University School of Public Health professor, told Global News. Tweet This

He studies the health risks tied to obesity and the implications for people who are at-risk.

READ MORE: Obesity rates have tripled in Canada in less than 3 decades

“The notion of healthy obesity is controversial because we currently lack tools that are both accurate and practical for risk stratification in obesity,” he said.

Take body mass index – or BMI – for example. It’s calculated by dividing a patient’s weight in kilograms by the square of the person’s height in metres. But it doesn’t distinguish fat from muscle mass, a major flaw that mislabels many people.

Story continues below advertisement

In other research, those who are obese are compared to peers with a regular weight without considering the lifestyle factors of those with an average weight. Maybe they smoke or drink, or are dealing with chronic diseases that tamper with their weight.

“The problem here is that whenever people in the normal weight category are compared to those in the overweight or obese categories, it can appear that the latter are healthier because some people in the normal weight group are actually very sick people who became normal weight after developing a serious condition, such as heart disease or cancer,” Stokes explained. Tweet This

Up to 30 per cent of people who are classified as obese are “metabolically healthy” and may not be getting enough obesity-related help with their health, Ryden warned.

READ MORE: Are you still using BMI to measure your health? Don’t, docs say

In Ryden’s study, he looked at 15 healthy, never-obese people next to 50 obese people. He wanted to measure the white fat tissue along their waistline, along with their insulin response.

Turns out, it didn’t matter if you were healthy obese or just obese when it came to stimulating insulin. The abnormal gene expression patterns in people who were obese were there even after the doctors controlled for gender, waist-to-hip ratio, heart rate and blood pressure.

Story continues below advertisement

This isn’t the first study to debunk the healthy obesity theory.

Last year, British scientists out of University College London said that within 20 years, the excess weight will catch up with your health.

“A core assumption of healthy obesity has been that it is stable over time, but we can now see that healthy obese adults tend to become unhealthy obese in the long-term,” according to lead author Joshua Bell.

READ MORE: How this Danish doctor is battling childhood obesity around the world

“Healthy obesity is only a state of relative health – it’s just less unhealthy than the worst-case scenario,” he warned.

The study was based on more than 2,500 people whose health was tracked for 20 years. Their body mass index, cholesterol, blood pressure and insulin levels were all measured.

People who fell under the “healthy obesity” category were considered obese without any present risk factors.

READ MORE: This anti-obesity ad may scare parents into stashing the junk food away

But within the two-decade time frame, more than 51 per cent of the healthy obese participants joined their unhealthy obese counterparts.

Ryden’s full findings were published Thursday in the journal Cell Reports.

Story continues below advertisement

carmen.chai@globalnews.ca

Follow @Carmen_Chai