“But it doesn’t have to be vigorous activity or playing team sports, you just have to move about.
“Being active could be things such as gardening, walking or other activities that you can build into your daily routine.”
The study examined particular genes linked to exercise, to identify the most active men, and compare their disease rates with those of less active participants.
Dr Lewis said: “This study is the largest-ever of its kind which uses a relatively new method that complements current observational research to discover what causes prostate cancer.
“It suggests that there could be a larger effect of physical activity on prostate cancer than previously thought, so will hopefully encourage men to be more active.”
Dr Anna Diaz Font, head of research funding at the WCRF, said: “Up till now, there has only been limited evidence of an effect of physical activity on prostate cancer.
“This new study looked at the effect of 22 risk factors on prostate cancer, but the results for physical activity were the most striking.
“This will pave the way for even more research, where similar methods could be applied to other lifestyle factors, to help identify ways men can reduce their risk of prostate cancer.”
Prostate cancer mostly affects men over the age of 50 and risk factors include having a family history of the disease.
Almost 48,000 men in the UK are diagnosed with prostate cancer each year and it kills almost 12,000 men annually.
The study was published in the International Journal of Epidemiology.