American Cancer Society said in new guidelines that maintaining healthy weight in cancer survivors is most essential task.
The report said obesity is a well-established risk factor for some of the most common forms of cancer, including breast cancer in post-menopausal women and cancers of the colon, esophagus, liver, gallbladder, pancreas, kidney, uterus and prostate.
It also cited increasing evidence that being overweight raises the risk for recurrence and reduces likelihood of survival for many cancers.
The American Cancer Society said nearly two-thirds of U.S. cancer patients live more than five years after diagnosis, and more than 10 million Americans now alive have been diagnosed with cancer at some time in their lives.
Vegetarian diets can have many benefits because they tend to be low in saturated fat and high in fiber and vitamins.