Is it true that 'healthy obesity' boosts death risk?

Metabolically healthy obesity — also known as "healthy obesity" — describes obesity not accompanied by metabolic health complications, such as diabetes, hypertension, or high cholesterol.

There are many debates about how "healthy" metabolically healthy obesity actually is, and whether it renders people more vulnerable to other health problems in the long run.

As recently as last month, Medical News Today reported on a study that suggested that healthy obesity does, in fact, put certain people at a higher risk of cardiovascular disease.

But what about the risk of premature death? This is the question asked by a team of researchers from York University in Toronto, Canada, and the University of South Carolina in Columbia.

The researchers — whose efforts were guided by Jennifer Kuk, an associate professor at the School of Kinesiology and Health Science at York University — found that obesity alone, in the absence of hypertension, dyslipidemia (high cholesterol), and diabetes, is not associated with a heightened mortality risk.

These findings — which are described in a paper published in the journal Clinical Obesity — counter previous assumptions and may pose important questions about current guidelines regarding the care of people diagnosed with obesity.

Findings 'in contrast with most literature'

Kuk and team specifically defined "healthy obesity" as obesity that occurs in the absence of any metabolic risk factors. The researchers analyzed health-related data from 54,089 participants — both women and men — who had been involved in five different cohort studies.

They compared the mortality risk of people with obesity but without metabolic diseases with that of people with obesity accompanied by a metabolic problem, and then again with the mortality risk of healthy people, without obesity and without metabolic risk factors.

What they found was that obesity, on its own, did not increase the risk of premature death. This was in contrast with other metabolic risk factors — including diabetes, dyslipidemia, and hypertension — all of which do increase mortality independently.

"This is in contrast with most of the literature and we think this is because most studies have defined metabolic healthy obesity as having up to one metabolic risk factor," notes Kuk.

"This is clearly problematic, as hypertension alone increases your mortality risk and past literature would have called these patients with obesity and hypertension, 'healthy.' This is likely why most studies have reported that 'healthy' obesity is still related with higher mortality risk."

Jennifer Kuk

Benefits of weight loss 'questionable'

Obesity is diagnosed for individuals with a BMI of 30 or above, and the researchers point out that current recommendations advise that people aim to lose weight if they hit this mark.

However, 1 out of 20 people with obesity do not have any other metabolic problems, Kuk and team found. And if this is the case, they ask, will losing weight actually bring any benefits to people with a BMI of 30 or over?

"We're showing that individuals with metabolically healthy obesity are actually not at an elevated mortality rate," says Kuk. "We found that a person of normal weight with no other metabolic risk factors is just as likely to die as the person with obesity and no other risk factors," she adds.

"This means," Kuk stresses, "that hundreds of thousands of people in North America alone with metabolically healthy obesity will be told to lose weight when it's questionable how much benefit they'll actually receive."

Below, you can watch Jennifer Kuk explaining the findings of the new study, and their possible implications for existent public health guidelines.