It’s never too late to become active, and strive to get fit. According to this article, from Nubella Health & Nutrition:
You can still improve your heart health by up to 90 percent by starting or increasing physical activity later in life, regardless of your age.
The article cites a study from German researcher Dr. Dietrich Rothenbacher. Thats good news for anyone who suffers from heart problems. Nubella has been on a role lately, as they also posted an article citing a different study on the benefits that exercise has on preventing dementia, Alzheimer’s disease, and general cognitive impairment. Notably:
Middle-aged people who were physically active at work and leisure more than twice a week enjoyed a 50-percent and 60-percent lower risk than sedentary people of developing dementia and Alzheimer’s respectively.
Nubella followed up with a few bits of advice, "10 Ways to Get Moving". It has some pointers for sedentary folks who would like to change their ways, but aren’t sure where to start.
All of these new studies on the benefits of exercise are interesting, in that the researchers have come up with numbers and facts to support the widely known common sense platitude, that exercise is a healthy thing to do. They’re finding out just how healthy it is. If one takes a moment to consider from where we came, how we evolved, it is no surprise that disease and illnesses often go hand in hand with lack of exercise. 
For millions of years, survival was a struggle. Movement was a prerequisite to staying alive. Had we evolved to sit around, our bodies would probably look more like plants. Potatoes, perhaps. However, thats not how we turned out — we are designed, via natural selection, to move, to use our muscles, to run, to sweat. To stop doing these things is to deny ourselves of that which makes us human, that which makes us alive.
