Researchers from the National Cancer Institute and Harvard Medical School analyzed studies of more than 630,000 people.
They found that regular, moderate-intensity exercise can boost life expectancy even with an unhealthy BMI, or body mass index.
On the flip side doctors say healthy-weight people who don't exercise had about three fewer years of life.
Researchers say people should get at least two-and-a-half hours of moderate to vigorous exercise each week.
