Obesity and overweight increase the risk and worsen the prognosis of cancer and are the primary risk factors for numerous diseases such as cardiovascular disease type 2 diabetes and metabolic syndrome. Obesity has been shown to be an independent risk factor for some cancers including breast cancer endometrial cancer ovarian cancer gastric cancer colorectal cancer renal cancer esophageal adenocarcinoma pancreatic ductal adenocarcinoma and liver cancer. The mechanism of obesity - promoting cancers which largely focuses on insulin resistance fat factor imbalance sex hormone imbalance systemic inflammation immune system alterations and intestinal flora imbalance after obesity is poorly understood. These systems interact and support carcinogenesis on the basis of inflammation they do not function independently. Most of the effects of obesity on the development and mortality of cancer can be prevented by adjusting diet and increasing physical exercise. Anti-inflammatory-based drug therapy can be used as a priority strategy for prevention and bariatric surgery also provides more options for preventing and treating obesity-related cancer. The mechanism by which obesity and overweight contribute to the formation and development of cancer will be discussed in this article along with future strategies for treating and preventing cancer in obese people.