virginiacolonoscopy.com

This report was based on a study that made projections of future levels of colorectal cancer if obesity and physical activity remain at their current levels. It compared these projections to hypothetical situations where everyone had optimum weight and exercise levels. An optimum body mass index (BMI) was predicted to reduce cases of colorectal cancer by up to 18.2% in men and 4.6% in women.  Optimum physical activity levels could reduce the risk by 11.6% in men and 21.2% in women.

This was a hypothetical model and these figures are only estimates that need further confirmation. However, in general, it is well established that maintaining a healthy weight, eating a balanced diet, getting enough exercise and avoiding smoking and excess alcohol are the best ways to remain healthy.
Read more from NHS Choices.