It is never too late to start exercising.

And whether you are 30 years old or 90, exercises such as running and lifting weights can help reverse the signs of aging.

“It is always best to start early,” says Dr. Mark Tarnopolsky, director of the neuromuscular and neurometabolic units at McMaster University Medical Centre in Hamilton, “but it is important that in our studies we also see major benefits in previously inactive older adults who complete four or six months of weight training.”

Tarnopolsky and colleagues have been studying what actually happens inside the body when people exercise. They have found quite a few benefits at the molecular level: Reduced fat in the body, increased muscle mass and decreased cell damage from aging. These effects occur even in 90-year-olds.

Exercising makes a difference in the way our genes act. The McMaster research shows that 579 genes in muscles start acting differently as we age.

In one of Tarnopolsky’s studies, 33 per cent of these genes went back to normal in people who did six months of weight training twice a week.

“We have also shown that resistance exercise improves some of the biomarkers of aging,” says Tarnopolsky. Biomakers are substances in the blood which signal disease or decay.

Running also seems to help people fight the effects of aging. A study conducted in northern California by researchers at Stanford University found that runners live longer than non-runners.

This study followed almost 1,000 people — about half were members of a running club and the other half were non-runners — for more than 20 years. All the participants were over 50 when the study started in 1984. After 19 years, only 15 per cent of runners had died, versus 34 per cent of non-runners.

This difference in survival rates continued to broaden as time went on. At 21 years, runners had a 50 per cent lower risk of death than non-runners.

In study after study, it has been shown that being physically active can help you fend off diseases such as type 2 diabetes, heart disease and even some types of cancer.

Special bonus: You’ll look great and feel great!