Packing on the extra pounds might actually help Canadians live longer, a new study has found.
Using body mass index as a measure, the study examined 11,326 adult Canadians over 12 years and found that overweight people were 17 per cent less likely to die than people with normal weight. Normal weight is defined as having a BMI of between 18.5 and 25, with those classified as overweight having a BMI of between 25 and 30.
The findings were published online in the research journal Obesity and give support to similar studies previously done in the United States that indicated a bit of excess weight might protect against premature mortality.
"I think this is part of an accumulation of evidence that indicates that organizations like Health Canada… should rethink the evidence on their classification of BMI categories," says David Feeny, one of the study's co-authors and a researcher with the Kaiser Permanente Center for Health Research in Oregon.
The study was a joint effort between Canadian and American researchers, using data from the National Population Health Survey conducted by Statistics Canada between 1994 and 2007. Other results found that extremely underweight people have a 70 per cent greater chance of dying than people of normal weight, with the extremely obese 36 per cent more likely to die.
Mr. Feeny speculates that overweight people might survive longer because their extra heft gives them more resilience when they become old or ill. Since people lose fat faster than muscle, having that bit of extra weight might help in preventing frailty.
He also says doctors nowadays are likely more proficient at detecting and treating maladies associated with excess weight.
"Being overweight was more of a penalty about a generation ago than it was now," he says. "Medical care systems are much more aggressive about screening and treating… and as risk factors associated with being obese arise, those are treated and ameliorated."
But the finding should not be seen as a reason to overindulge. Mr. Feeny emphasizes that his study only measured mortality rates, not morbidity, and some overweight Canadians included in the study could well have developed chronic diseases linked to excess weight such as cardiovascular disease, diabetes, hypertension or cancer.
Indeed, a separate research paper published in yesterday's issue of the Journal of the American Medical Association found that young adults who are overweight or obese are at increased risk of pancreatic cancer, the fourth-leading cause of cancer death in Canada.
"[Overweight people]live longer but how well do they live?" Mr. Feeny says. "Our results do not imply that if you're in the normal weight range, you should go out and try to gain weight."