THURSDAY, April 26 (HealthDay News) -- A healthy lifestyle -- including eating right, exercising and maintaining normal weight -- can boost the odds of long-term cancer survival, especially for breast, colorectal or prostate cancer, according to new recommendations from the American Cancer Society.

About one in 25 Americans is a cancer survivor. "Many ask, 'How can I keep the cancer from coming back?' " said Colleen Doyle, the cancer society's director of nutrition and physical activity.

Cancer survivors often are advised to adopt healthy behaviors, including eating lots of fruits, vegetables, whole grains and lean protein; fitting in walking or other aerobic activity most days of the week; and keeping weight within a normal range, Doyle said.

Research has shown that those steps can help prevent cancer, but there was little research showing that a healthy lifestyle could keep cancer from recurring, or could prevent cancer survivors from getting a new type of cancer, she said.

But a review of recent scientific evidence allowed a panel of cancer experts to conclude that such measures help ward off cancer's return.

"The last time we published recommendations for survivors in 2006, we didn't feel there was enough evidence to say clearly that watching your weight, being active and eating a healthy diet can reduce risk of recurrence," said Doyle, a co-author of the guidelines. "Since that time, 100 studies have looked at the impact of weight, diet or a combination of those things, and those studies have clearly formed a foundation for us being able to make these very solid recommendations that adopting a healthy lifestyle is one of the most important things cancer survivors can do for themselves."

The recommendations were published online April 26 in CA: A Cancer Journal for Clinicians.

Among the recommendations:

• Losing weight if you're overweight or obese may help prevent recurrence and development of new cancers. Obesity is associated with multiple types of cancer, including breast, colorectal and gallbladder malignancies.
• Exercise is "safe and feasible" during cancer treatment, and it also can improve physical functioning, fatigue and quality of life. People undergoing chemotherapy or radiation may need to reduce the intensity, but should strive to maintain physical activity to the extent possible. People who were sedentary before the diagnosis can begin low-intensity exercises such as stretching or brief, slow walks.
• Results from observational studies suggest that diet may affect cancer progression, risk of recurrence and survival in individuals treated for cancer. A diet high in fruits, vegetables, whole grains, poultry and fish was found to be associated with reduced mortality compared to a diet high in refined grains, processed and red meats, desserts and high-fat dairy products.
• No evidence shows that supplements benefit cancer survivors, and there is some evidence that certain supplements may cause harm.

Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City, said the guidelines support what oncologists have told patients for years, and the American Cancer Society's endorsement of that advice is an important step.

After a cancer diagnosis, adopting a healthy lifestyle also can help people regain a sense of control, Bernik added.

"When you have cancer, it takes control of your life. You have to go through the treatment and you feel it's ruling your life," she said. "After it's over, it's good when you feel you can take control."

Nothing is a sure thing, though, "and we have to tell them that," Bernik said. "But it helps emotionally knowing that they're doing something to prevent the cancer from recurring."

People diagnosed with cancer are at a significantly higher risk of developing other cancers, and may be at higher risk of developing other chronic diseases such as cardiovascular disease, diabetes and osteoporosis, said Nagi Kumar, director of cancer chemoprevention at Moffitt Cancer Center in Tampa, Fla.

"Many survivors are not going to die of cancer anymore," Kumar said. "They are going to have problems with obesity, metabolic syndrome and other diseases that are very common in the U.S. anyway, and this is a little bit more vulnerable group."

After months of treatment, it's important for cancer survivors to work to get their strength back and improve their aerobic capacity.

"It's really important to be obsessive about what they do for themselves," Nagi said. "Give it your all: do yoga, get more flexible, walk, eat right. Become very obsessive about what you're putting in your body."

More information

The U.S. National Cancer Institute has more on how lifestyle can help prevent cancer.