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'Healthy obesity" is a myth, according to new findings from Canadian researchers that counter the notion that some people can be overweight without suffering serious health consequences.

Compared to individuals of normal weight, obese people are at significantly increased risk of premature death – even in the absence of metabolic red flags such as high cholesterol, hypertension or blood-sugar levels associated with type 2 diabetes, according to the study by researchers at Mount Sinai Hospital in Toronto, published Monday in the Annals of Internal Medicine.

The popular notion that roughly a third of obese individuals do not suffer the negative consequences of obesity is based on short-term observation studies, said co-author Dr. Bernard Zinman, senior investigator at Mount Sinai's Lunenfeld-Tanenbaum Research Institute.

In a systematic review of long-term studies, however, "you see, in fact, that there is no such thing as healthy obesity," he said.

The Mount Sinai researchers analyzed data from eight separate studies involving more than 60,000 individuals. In each study, participants were defined as normal weight, overweight or obese, and their cholesterol, blood sugar and blood pressure were monitored.

Across the three weight categories, the studies compared fatal and non-fatal cardiovascular events, such as heart attack and stroke, as well as other causes of death.

The researchers found that after 10 or more years of follow-up, obese people had a 24-per-cent additional risk for a cardiovascular event or premature death compared to those of normal weight, regardless of whether obese individuals had metabolic problems at the outset.

"Any degree of obesity – whether it's associated with metabolic abnormalities or not – is a risk factor," Zinman said.

The study confirms previous research showing that obesity may be a ticking time bomb.

A large Australian study published in August, 2013, in the journal Diabetes Care concluded that "healthy obesity" may be a transition state that deteriorates over time.

The Australian study followed more than 4,000 individuals for up to a decade, and found that "healthy obesity" was a transient state for one-third of obese individuals initially classified as "metabolically healthy."

The health consequences of obesity worsen over time, Zinman noted, adding that many individuals remain obese for much longer than the 10-year duration of recent studies. "One of the things that concerns us greatly is that obesity is occurring in children," he said.

Leaner individuals do not necessarily get a clean bill of health. The Mount Sinai review found increased health risks in individuals with metabolic problems at any weight. However, people of normal weight are "much less likely" to develop metabolic problems in the first place, Zinman pointed out.

"We should be striving to prevent obesity," he said.

The authors of an accompanying editorial in the Annals of Internal Medicine concurred: "Accepting that no level of obesity is healthy is an important step toward deciding how best to use our resources and our political will to develop and implement strategies to combat the obesity epidemic," they wrote.