Living a healthier lifestyle could cut your risk of cancer in half, scientists say.

Exercising, eating well, keeping your weight at the right level, and not smoking are all keys to preventing cancer.

The number of cancer cases in the U.S. has been falling slowly in recent years. But scientists say more progress could be made.

A new study finds smoking can be blamed for one-third of all cancer cases in the U.S.

"For people who do not smoke, excess weight and lack of sufficient physical activity may be among the most important risk factors for cancer," John Seffrin, CEO of the Cancer Society, said in a statement.

Cancer is the second deadliest illness in the U.S., behind heart disease.