Recent international cancer prevention guidelines recommend weight loss, where appropriate, for the purpose of cancer risk reduction. However, limited research associates voluntary weight loss to subsequent cancer incidence because of the difficulty of achieving long-term weight loss maintenance among large participant groups. Bariatric surgery has demonstrated long-term sustained weight loss, and as a result, patients after bariatric surgery represent an ideal population to explore the relationship between long-term, voluntary weight loss and cancer incidence. This paper briefly reviews cancers that have shown to be associated with overweight and obesity and looks at studies that demonstrate reduced total mortality after bariatric surgery. Reduced cancer mortality and incidence as well as reduced cancer-related physician visits after bariatric surgery are presented. Study limitations and future research questions related to cancer and bariatric surgery are briefly discussed.