A study of over 4,000 people finds even those who make the switch in their late 40s and 50's can still benefit.
Researchers looked at markers linked to heart problems such as inflammation.
In the study, published in the journal Circulation, people who did the recommended 2.5 hours of exercise a week saw improvement and had lower levels of inflammation.
But, doctors also say it's important not to wait till you retire to get off the couch.
