Experts often talk about how your lifestyle affects your risk of developing cancer. For instance, scientists writing in the latest issue of the British Medical Journal are currently warning that women who smoke at any time during their life could be at an increased risk of developing breast cancer (that's right, even if you gave up smoking years ago).
Taking regular exercise, they say, could make you 16 less likely to develop the large, advanced polyps that medics believe are the most likely to develop into bowel cancer.
The study analysed information from 20 other studies on the link between exercise and the development of polyps. It claims there is a definite association between the amount of exercise you do and the likelihood of your developing polyps - but it can't explain exactly why.
It could be something to do with the way exercise boosts the immune system, they suggest, or how regular exercise reduces inflammation in the bowel and lowers insulin levels, all of which have been linked to a lower bowl polyp risk.
There's also no firm recommendation by the study's authors on exactly how much exercise you should do, but Cancer Research UK experts are recommending half an hour's moderate exercise a day.