Overweight and obese individuals have the potential to decrease their life expectancy by up to eight years, according to a recent study.

New research from scientists at McGill University and McGill University Health Center further demonstrate that when one considers that these individuals may also develop diabetes or cardiovascular disease earlier in life, this excess weight can rob them of nearly two decades of healthy life.

"Not only is excess body weight associated with a significant reduction in life expectancy, but with an even greater reduction in healthy life years," Dr. Steven Grover, lead researcher of the study and a professor of medicine at McGill University, told HealthDay. "While losing weight or exercising regularly is not easy for many of us, the potential benefits are huge."

For the study, researchers used data from the national Health and Nutrition Examination Survey to develop a model that estimates the annual risk of diabetes and cardiovascular disease in adults with different body weights. This data from almost 4,000 individuals was also used to analyze the contribution of excess body weight to years of life lost and healthy years of life lost.

Their findings estimate that individuals who were very obese could lose up to eight years of life, obese individuals could lose up to six years, and those who were overweight could lose up to three years.

In addition, healthy life-years lost were two to four times higher for overweight and obese individuals compared to those who had a healthy weight, defined as 18.5 to 25 body mass index (BMI). The age at which the excess weight accumulated was an important factor and the worst outcomes were in those who gained their weight at earlier ages.

"The pattern is clear -- the more an individual weighs and the younger their age, the greater the effect on their health," Grover adds. "In terms of life-expectancy, we feel being overweight is as bad as cigarette smoking."

The findings are detailed in The Lancet Diabetes and Endocrinology.