The idea that a person can be obese and healthy is a myth, doctors have said.

Despite their increased body fat, some obese people have normal metabolic features, such as normal blood pressure and cholesterol levels. Until now, this have been referred to as ‘benign obesity' or ‘metabolically healthy obesity'.

However, this latest research from Canada dispels this myth. Doctors reviewed eight studies involving over 61,000 people. Each study looked at people who were a normal weight, overweight and obese.

The metabolic status of each person was studied and fatal and non-fatal heart-related events, such as heart attacks and stroke, were compared. Other causes of death were also looked at.

The study found that people who were obese carried an additional risk of dying prematurely regardless of their metabolic status when compared with people of a normal weight.

"Our research findings challenge the myth that there is such a thing as healthy obesity if people maintain normal-range readings of cholesterol, blood glucose and blood pressure," commented the study's co- author, Dr Ravi Retnakaran, of Mount Sinai Hospital in Toronto.

He pointed out that even in the absence of high blood pressure or cholesterol, an obese person ‘may be at 24% additional risk' of suffering a heart-related event or dying prematurely compared to a person of normal weight.

"The finding of increased risk of death or cardiovascular events for obese individuals suggests that gaining excess weight is associated with risk that may accumulate over time, even before metabolic and cardiovascular signs become apparent in lab tests. This is a signal to GPs to guide their obese patients to weight loss, regardless of lab tests," Dr Retnakaran said.

The doctors noted that when they compared the three weight groups - normal, overweight and obese - they found that obesity ‘stood out as the key risk factor for premature death from any cause, including cardiovascular events'.

"That's true for obese people with so-called healthy metabolic status as well as obese people with poor metabolic status - that is, high blood pressure, cholesterol and blood glucose levels," commented senior investigator, Dr Bernard Zinman, also of Mount Sinai Hospital.

The study also showed that even if a person is of a normal weight, if they have a poor metabolic status, they are also at risk.

"The idea that we don't need to target healthcare resources toward obese people whose lab tests are ‘normal' turns out to be false. Our message to physicians is that for obese individuals, normal metabolic status regarding blood pressure, cholesterol and blood glucose is not protective. If they can start to lose weight, that's a benefit," added the study's lead author, Dr Caroline Kramer.

Details of these findings are published in the journal, Annals of Internal Medicine.