Dr. David Euhus, professor of surgery at the University of Texas Southwestern Medical Center in Dallas, said there is a link between being overweight and an increased risk for breast and other forms of cancer.
In addition, regular physical activity is associated with reduced cancer rates and better survival rates for people who do get cancer, Euhus said.
"There are dozens of cancer prevention diets being promoted right now, but not one of them has ever been shown to reduce cancer rates in clinical trials," Euhus said in a statement. "It's all about lifestyle. Fad diets work for a time, but it is important to actually change the way you live."
Overweight people tend to have elevated levels of insulin and other hormones that promote growth of cancer cells, and people who carry excess weight around their midsections seem to have the highest increased risk, Euhus noted.
Experts recommend avoiding simple sugars found in desserts and candy, never eating more calories than one can burn off, and exercising three to five times a week to break a sweat and elevate the heart rate, Euhus said.