According to a recent study by Cancer Research UK 6.3% of all cancer cases were caused by being overweight or obesity. A close second to smoking which was top and third place was sun exposure 3.8% (http://www.bbc.co.uk/news/health-43502144).
Although the cases for smoking and cancer has dropped to 15.1% from 19.4% it is still a high-risk factor. This study also showed that cancer could be preventable by changing some of your basic lifestyle choices.
The preventable causes of cancer are: