Leisure-time physical activity is associated with longer life expectancy, even at relatively low levels of activity and regardless of body weight, according to a study by a team of researchers led by the National Cancer Institute (NCI), part of the National Institutes of Health. The study, which found that people who engaged in leisure-time physical activity had life expectancy gains of as much as 4.5 years, appeared Nov. 6, 2012, in PLoS Medicine.

In order to determine the number of years of life gained from leisure-time physical activity in adulthood, which translates directly to an increase in life expectancy, researchers examined data on more than 650,000 adults. These people, mostly age 40 and older, took part in one of six population-based studies that were designed to evaluate various aspects of cancer risk.

The U.S. Department of Health and Human Services, the parent agency of NIH, recommends that adults ages 18 to 64 engage in regular aerobic physical activity for 2.5 hours at moderate intensity -- or 1.25 hours at vigorous intensity -- each week. Moderate activities are those during which a person could talk but not sing. Vigorous activities are those during which a person could say only a few words without stopping for breath.

After accounting for other factors that could affect life expectancy, the researchers found that life expectancy was 3.4 years longer for people who reported they got the recommend level of physical activity. People who reported leisure-time physical activity at twice the recommended level gained 4.2 years of life. In general, more physical activity corresponded to longer life expectancy.

The researchers even saw benefit at low levels of activity. For example, people who said they got half of the recommended amount of physical activity still added 1.8 years to their life.

"Our findings highlight the important contribution that leisure-time physical activity in adulthood can make to longevity," said study author Steven Moore, Ph.D., of NCI's Division of Cancer Epidemiology and Genetics, and lead author of the study. "Regular exercise extended the lives in every group that we examined in our study -- normal weight, overweight, or obese."

The researchers found that the association between physical activity and life expectancy was similar between men and women, and blacks gained more years of life expectancy than whites. The relationship between life expectancy and physical activity was stronger among those with a history of cancer or heart disease than among people with no history of cancer or heart disease.

The researchers also examined how life expectancy changed with the combination of both activity and obesity. Obesity was associated with a shorter life expectancy, but physical activity helped to mitigate some of the harm. People who were obese and inactive had a life expectancy that was between five to seven years shorter (depending on their level of obesity) than people who were normal weight and moderately active.

Physical activity has been shown to help maintain a healthy body weight, maintain healthy bones, muscles and joints, promote psychological well-being, and reduce the risk of certain diseases, including some cancers.

"We must not underestimate how important physical activity is for health -- even modest amounts can add years to our life," said I-Min Lee, M.D., Sc.D. , professor of Medicine, Harvard Medical School, Cambridge, Mass., and senior author on the study.

This work was supported by NCI's Division of Cancer Epidemiology and Genetics under intramural project number ZIACP010196 and by NCI's Division of Cancer Control and Population Sciences under grants CA105069 and CA047988. Additional support was received from two other parts of the NIH, the National Institute on Aging (AG18033), and the National Heart, Lung, Blood Institute (HL043851 and HL080467).