Many investigations around the world try to identify risk factors for cancer, especially avoidable ones. But each person is free to make their own decisions: tobacco is the avoidable carcinogen that causes more deaths and, although this is known, many people continue to smoke.

In 2002 the World Health Organization (WHO) issued a report warning that obesity itself (regardless of its cause) is a factor that increases the likelihood of cancer. Specifically, this body referred to colorectal cancer, esophageal, kidney, endometrial cancer and breast cancer in postmenopausal women.