Professor Tim Key tells us about the role of life style and diet in the development of cancer. Although smoking is still the most important cause of cancer, we now know that obesity and high intakes of alcohol can increase the risk of several types of cancer. Professor Tim Key is researching the role of diet and hormones in the development of cancer, particularly cancers of the breast, prostate and bowel. Professor Key is the principal investigator of the EPIC-Oxford cohort of sixty thousand participants, for various studies on cancer, hormones and nutrition.