It will be no surprise to many of us that being physically fit helps protect against heart disease, but a person’s level of fitness might also have a profound effect on cancer outcomes long before a diagnosis.

According to a new study in JAMA Oncology, men who were very fit in middle age were 32% less likely to die from cancer after being diagnosed after age 65 than men who weren’t fit in midlife. Very fit men in their late 40s are less likely to get lung cancer and colorectal cancer than unfit men.

The study involved a comprehensive fitness test of 13,949 menin the USA. They were split into three fitness groups: lowest 20%, middle 40% and top 40%, and followed for an average of 6.5 years to see if fitness affected their chance of developing certain cancers.

Men in the fittest group were 55% less likely to develop lung cancer and 46% less likely to develop colorectal cancer compared with men in the lowest fitness group.

Perhaps surprisingly, men in the top group actually had a 22% higher risk of prostate cancer.

One obvious point is that men who exercise to stay fit are usually healthy in other ways too, such as eating a healthy diet and abstaining from alcohol. This could have influenced the results.

Still, there is evidence that exercise alone can reduce your cancer risk.  With its proven effect of preventing heart disease, regular exercise is always a good idea, whatever your age or sex.