By Elizabeth Cohen
Senior Medical Correspondent

We’ve always heard it’s healthier to be thin – but a new study says you’ll actually live longer if you’re a bit overweight.

Researchers at Kaiser Permanente in Portland, Oregon followed 11,326 adults in Canada for twelve years. They found that those who were overweight were 17% less likely to die during the twelve years of the study.

They defined overweight and normal weight by the Body Mass Index chart, which says that someone who’s five-feet-four-inches tall would be considered normal weight at 110 to 140 pounds, and overweight would be 145 to 169 pounds. For someone who’s five-foot-ten, normal weight would be 132 to 167 pounds, and overweight would be 184 to 213 pounds.

“It is surprising carrying a little extra weight may give people a longevity advantage,” said David Feeny, a coauthor of the study. “It may be that a few extra pounds actually protect older people as their health declines.”

So does this mean it’s okay to be overweight? The study authors say no. They say the results illustrate that weight is only one factor in health. “Good health is more than BMI or a number on a scale. We know that people who choose a healthy lifestyle enjoy better health: good food choices, being physically active every day, managing stress, and keeping blood pressure, cholesterol, and blood sugar levels in check,” says Dr. Keith Bachman, a co-author of the study, which was published online in the journal Obesity.

The study also found that underweight people had the highest risk of dying during the study, and the extremely obese had the second highest risk. For someone who’s five foot four, underweight is below 110 pounds, and extremely obese is over 232 pounds.

So are you overweight? Use this tool to calculate your BMI.