There are some case-control studies and cohort studies whose results suggest that obesity is positively associated with the risk of colon carcinogenesis, but the association with rectal cancer is not certain. However, there are also some studies that have not found an association between high BMI (Body Mass Index, also known as Body Mass Index in English) and colon and rectal cancer, and even the opposite has been reported. From an etiological point of view, perhaps obesity is a concomitant form of high-risk status for colon cancer, and the association between obesity and tumors is affected by many factors, such as diet, alcohol consumption, smoking, physical activity, hypertension, diabetes mellitus, and the status of sex hormone balance, etc., so that obesity should be considered comprehensively in evaluating its role in tumorigenesis. The results of some case-control studies and cohort studies suggest that obesity is positively associated with the risk of colon carcinogenesis, but the association with rectal cancer is not certain. However, there are also some studies that have not found an association between high BMI and colon and rectal cancer, and even the opposite has been reported. From an etiological point of view, perhaps obesity is a concomitant form of a high-risk state for colon cancer, and the association between obesity and tumors is influenced by many factors, such as diet, alcohol consumption, smoking, physical activity, hypertension, diabetes mellitus, and the status of sex hormone balance, etc., so that obesity should be considered comprehensively in evaluating its role in tumorigenesis.