Exercise boosts life expectancy, even in those who are obese, a new study found. Researchers say that moderate to vigorous activities like brisk walking can add 3.5 years or more to your lifespan.

In the study, researchers from Brigham and Women's Hospital analyzed data from 650,000 adults who were part of six different studies. They examined the effects of moderate to vigorous exercise on their health. On an average, they tracked a participant for ten years.

Brisk walking for an hour or so every day reduced people's risk of dying early by as much as 19 percent and this positive effect on health remained irrespective of the person's weight.

"We found that adding low amounts of physical activity to one's daily routine, such as 75 minutes of brisk walking per week, was associated with increased longevity: a gain of 1.8 years of life expectancy after age 40, compared with doing no such activity. Physical activity above this minimal level was associated with additional gains in longevity," said Dr. I-Min Lee, associate epidemiologist in the Department of Preventive Medicine at BWH and senior author on this study.

Lee added that people who walked for 450 minutes or about 7.5 hours a week tended to gain 4.5 years of life. The trend remained the same for people of all sizes - normal, overweight and obese.

Researchers found that moderate to vigorous exercise of 95 minutes added 1.8 extra years to life while a similar intensity exercise over 2.5 hours per day could extend lifespan by 3.5 years.

"Our findings reinforce prevailing public health messages promoting both a physically active lifestyle and a normal body weight," said Dr. Steven C. Moore, research fellow at the National Cancer Institute and lead author of the study.

"You can't lose 30 pounds tomorrow. But you can start exercising," Moore told The Los Angeles Times.

The study, published in the journal PLOS Medicine, shows how moderate exercises and even the simpler ones like walking can add years to a person's life.

CDC says that people should get at least 150 minutes moderate intensity physical activity every week. A recent report from the federal agency had said that 62 percent of people in the U.S walk for about 10 minutes a week.