A new study from researchers at Harvard University has found that exercising later in life may help stave off chronic illnesses like cardiovascular disease, type 2 diabetes, and even some cancers, the school said in the Harvard Gazette, a university publication.

“It’s a widespread idea in Western societies that as we get older, it’s normal to slow down, do less, and retire,’’ said Harvard evolutionary biologist Daniel E. Lieberman, lead author of the study, in the Gazette story published Nov. 22. “Our message is the reverse: As we get older, it becomes even more important to stay physically active.’’

The article said the researchers, whose findings were published in the Proceedings of the National Academy of Sciences of the United States of America, “hypothesize’’ that humans have evolved to keep physically active as they age, and that doing so allocates energy to processes that slow the body’s gradual deterioration.

The study showed that in addition to burning calories, physical activity is also physiologically stressful, and the stress damages the body at the molecular, cellular, and tissue levels, according to the article. However, the study also found the body responds to the damage with a “build back stronger’’ bent, the article said, with cellular and DNA repair processes shown to lower the risk of diabetes, obesity, cancer, osteoporosis, Alzheimer’s, and depression.

“The key take-home point is that because we evolved to be active throughout our lives, our bodies need physical activity to age well,’’ Lieberman told the Gazette. “In the past, daily physical activity was necessary in order to survive, but today we have to choose to exercise, that is to do voluntary physical activity for the sake of health and fitness.’’

Lieberman stressed that the activity level needn’t be extreme to be effective.

“The key is to do something, and to try to make it enjoyable so you’ll keep doing it,’’ Lieberman told the Gazette. “The good news is that you don’t need to be as active as a hunter-gatherer. Even small amounts of physical activity — just 10 or 20 minutes a day —substantially lower your risk of mortality.’’

Lieberman expanded on that point in an e-mail to the Globe Wednesday.

“Even 10 minutes a day has an appreciable effect, and a little more is better if you can do it (but as you say, build up gradually),’’ Lieberman wrote, adding that it’s wise to “make it social. If it’s socially rewarding, you’ll be more likely to do it and enjoy it.’’

He also told the Globe the study focuses on some of the less heralded benefits of exercise.

“[W]hile I think people realize that exercise is healthy in part because it slows or prevents processes that are unhealthy (e.g. weight gain, excess sex steroid levels) we also show that the other reason exercise is healthy is that it turns on repair and maintenance processes to counter the stresses (structural and molecular) that physical activity causes,’’ Lieberman wrote.

Over time, he continued, “these R+M processes add up to a lot of calories! And crucially since we never evolved not to be physically active, we never evolved to turn them on as much without being physically active. All in all, our theory helps explain why exercise is healthy, and why its effects become more, not less, important as we age.’’

Travis Andersen can be reached at travis.andersen@globe.com. Follow him on Twitter @TAGlobe.