Does obesity increase cancer risk?

Yes. The national cancer institute, on its website, lists several cancers whose risks are increased in an obese person. The cancers are: breast cancer in post-menopausal women (women after menopause), endometrial cancer (cancer of the uterus' lining), colon cancer, kidney cancer, and esophagus cancer (the tube that carries food from the mouth to the stomach).
Yes. Obesity increases the risk of 13 different cancers. The most dramatic association is with cancer of the uterus, but obesity also increases the risk of breast, colon, kidney, pancreas, and others. The american cancer society estimates 15 to 20% of cancer deaths are due to obesity.