New Canadian research suggests being obese doesn't necessarily doom people to an early grave.

Two research teams using a new tool called the Edmonton Obesity Staging System, which ranks overweight and obese people on a five-point scale according to their underlying health, have found that not only can the scale predict who is at greater risk of dying, but that otherwise healthy obese people live as long as those of "normal" weight, and are less likely to die of cardiovascular causes.

The back-to-back studies come as more evidence emerges that a significant proportion of overweight people are metabolically healthy and that the risks associated with obesity do not make for a one-size-fits-all formula.

The Edmonton staging system grades obesity on a scale of zero to four. It uses physical measures such as body mass index, as well as waist-to-hip ratios. But it goes farther by taking into account the presence — or absence — of a spectrum of disease.

Under Stage 0, the person is obese, but has no apparent obesity-related health risks, meaning their blood pressure, blood fats and other risks are all within the normal range. Stage 1 obesity describes people with "sub-clinical" signs of trouble, such as borderline high blood pressure, elevated liver enzymes and occasional aches and pains. Stage 4 is the most severe. At Stage 4, patients have serious, "potentially end-stage" disabilities and illnesses from obesity-related diseases.

In one study published Monday in the Canadian Medical Association Journal, University of Alberta researchers tested the system using data from a survey of 8,143 people in two U.S. national health and nutrition surveys.

They found that although 77 per cent of overweight or obese people in one survey, and 90 per cent of those in another, were classified as Stage 1 or Stage 2, their risk of dying over 20 years of followup was substantially lower than people classified as Stage 3 obesity.

After adjusting for age, history of smoking and metabolic syndrome — a cluster of conditions such as high blood pressure and diabetes —about two per cent of people with scores of 0 or 1 died during followup, compared to about 40 per cent of Stage 3 patients.

"That's a huge difference," said Dr. Arya Sharma, who first proposed the Edmonton classification system.

"What this actually means is if I examine people today and I see that they're Stage 0 or Stage 1, I can tell them to eat as healthy and be as physically active as possible rather than running out and trying to lose weight," said Sharma, chair of obesity research and management at the University of Alberta in Edmonton.

In a second study, using a modified version of the Edmonton scale, researchers led by York University's Dr. Jennifer Kuk categorized 6,000 obese Americans according to the Edmonton obesity staging system and compared their risk of dying to 23,000 lean individuals over a 16-year span.

They found that obese people with no or only mild health problems had a similar risk of dying over the followup period as normal-weight people. In fact, patients in Stage 0 or 1 were at lower risk of dying from cardiovascular disease or coronary heart disease than normal-weight individuals.