walkingResearchers at the National Institutes of Health have found that leisure-time physical activity can increase life expectancy by as much as 4.5 years, even at relatively low levels of activity.

Results of the study by a team of researchers led by the NIH's National Cancer Institute (NCI) appeared Nov. 6, 2012, in PLoS Medicine.

Researchers examined data on more than 650,000 adults, mostly age 40 and older, and 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 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.

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.