The cancers most closely linked to excess weight are breast, endometrial, kidney, colorectal, pancreatic, esophageal and gallbladder.
The list is expected to increase as research continues, says Michael Thun, emeritus vice president of epidemiological research at the American Cancer Society.
"Several other types of cancer - liver, multiple myeloma and certain leukemias - have been linked to obesity in some studies, but this needs confirmation," Thun said.
Donna Ryan, an oncologist and president of the Obesity Society, says insulin is probably the link between obesity and cancer, though hormones and other factors play a part as well.
"Insulin resistance and elevated insulin levels frequently occur in obese people. Insulin is a very powerful cellular growth factor, and it affects cancer cells," Ryan explained.
Anne McTiernan, director of the Prevention Center at Fred Hutchinson Cancer Research Center in Seattle, says the best way to lower your risk of cancer is to lose weight, exercise and eat a healthy diet.
Read more at usatoday.com.