Canadians who are slightly overweight live longer than people of normal weight, according to a new study that confirms similar findings from the U.S.

The study of body mass index followed 11,326 people age 25 or older over a 12-year period. The results appear online in the journal Obesity.

"It may be that a few extra pounds actually protect older people as their health declines, but that doesn't mean that people in the normal weight range should try to put on a few pounds," Mark Kaplan, a co-author of the study and a professor of Community Health at Portland State University, said in a release Tuesday.

As expected, people who were extremely underweight had the highest risk of dying, followed by the extremely obese.

During the study period, from 1994/1995 through 2006/2007, underweight and extremely obese people were more likely to die than people of normal weight. People who were overweight were less likely to die than those of normal weight.

A BMI of 18.5 to 24.9 is considered a normal weight.

Specifically, the increased risk of mortality over the 12 years of followup was 1.73 times higher for underweight Canadians compared to those with normal weight.

The risk was 1.36 times higher for obese people with a BMI over 35, compared to people of normal weight.

In contrast, people who were slightly overweight (BMI 25 to less than 30) had 0.83 times lower risk of death compared with normal weight people.

The fact that most deaths are among the elderly could explain why a small amount of extra weight may reduce one's risk, said study co-author David Feeny of the Kaiser Permanente Center for Health Research.

"Being overweight may be protective as your health declines, as you have health shocks and you're less likely, as you lose a little weight with illness, to end up being really frail — because you had more to start with," Feeny said.

Data from Statistics Canada

Kaplan acknowledged that the study looked at mortality only, not quality of life. But people who choose a healthy lifestyle such as eating nutritiously and exercising regularly also tend to enjoy better health, he noted.

The researchers controlled for factors such as age, sex, physical activity and smoking.

The team used data from the National Population Health Survey conducted by Statistics Canada every two years.

A study conducted in the U.S. and published in 2005 in the Journal of the American Medical Association showed similar results.

The latest study was funded by the U.S. National Institute on Aging, the U.S. National Institute of Diabetes and Digestive and Kidney Diseases and the Canadian Embassy in Washington, D.C.

With files from The Canadian Press