Most of us recognize that obesity is not a benign condition. Diabetes, arthritis, plus heart, liver and gallbladder diseases commonly plague folks who carry major excess poundage. Less familiar is the risk of cancer. Being overweight or obese has been linked to at least 13 types of cancer. Obesity more than doubles the risk of the most common forms of uterine and esophageal cancer. It raises the risk of tumors of the colon, gallbladder, kidney, liver, pancreas, upper stomach and brain membranes by 50 to 80 percent compared with adults at a healthy weight, and it ups the odds for multiple myeloma and cancers of the breast, ovary and thyroid.