There's a straightforward way to live longer after being diagnosed with advanced cancer and it doesn't involve chemotherapy or surgery. It's just eating right and exercising more, doctors reported Wednesday.

Cancer survivors who followed standard American Cancer Society guidelines for healthy living were 42 percent less likely to die than similar survivors who didn't, researchers found.

"We found that patients who maintain a healthy body weight, engage in regular physical activity, and eat a diet rich in vegetables and whole grains and low in red meats and processed meats did better and survived longer than those who didn't," said Dr. Erin Van Blarigan of the University of California, San Francisco, who led the study.

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"I think the magnitude of the benefit was surprising," Van Blarigan told NBC News.

"Everyone seems to know that these behaviors are healthy and that people who do these things are going to live longer but I don't think anyone really appreciates how much better they might actually do."

The research is being featured at a meeting of the American Society of Clinical Oncology that starts next month in Chicago. And while the researchers studied colon cancer patients, they say their findings are likely to apply to many types of cancer survivors.

It may sound simple, but it's obviously not easy for cancer patients, Van Blarigan said.

"Only 10 percent of the patients in our study were actually doing it," she said. "So there is definitely a need for more resources and support to help patients adopt and maintain healthy lifestyles after they've been diagnosed with cancer."

For the study, Van Blarigan and colleagues followed 992 stage 3 colon cancer patients starting two months after they got surgery. They asked them about diet, weight and exercise and followed them for seven years.

Over that time, colon cancer came back in 335 of the people and 256 of them died.

They scored the volunteers for healthy behaviors: Eating at least 2 ½ cups of fruits and vegetables a day, eating whole grains instead of white flour and rice, keeping a healthy body weight, exercising at least half an hour a day — preferably an hour — and drinking moderately.

They found a clear, linear trend. The more people followed these guidelines, the less likely they were to have their cancer come back and the less likely they were to die.

"The people who were adhering to the guidelines in our seven-year follow-up period, 20 percent died," Van Blarigan said. "But in the group where people were not adhering to the guidelines, 35 percent died."

ASCO president Dr. Daniel Hayes said because people were watched in real time, it takes out mistakes that can happen when people are asked to look back on past behaviors.

"It makes these findings even more compelling, in my opinion," he told reporters.

There was another surprise in the study. Dr. Temidayo Fadelu of Massachusetts General Hospital and Harvard Medical School and colleagues looked specifically at whether the colon cancer patients ate nuts.

"We observed that nut consumption was associated with disease-free survival and overall survival," Fadelu told reporters.

Hardly any patients managed it, but those who did manage to eat at least two servings a week of tree nuts were also 42 percent less likely to die in the seven years, Fadelu and colleagues found. Peanuts, which are legumes, did not affect people's survival.

"We don't really know what the underlying biologic mechanism is for this association," Fadelu said.

With all the healthful behaviors, it could be that the body is responding better to insulin, the researchers said. The healthier eating and exercise may also lower overall inflammation in the body, which is linked to cancer risk, or it could alter the balance of the microbiome — the collection of microbes in the body.

"There are more than one million colorectal cancer survivors in the United States," said Van Blarigan. "These individuals are living longer than ever before, but the disease remains the second leading cause of cancer death in the U.S."

Colorectal cancer is the third most commonly diagnosed cancer in Americans, according to the American Cancer Society. Colon cancer will be diagnosed in more than 95,000 people this year and nearly 40,000 will be diagnosed with rectal cancer. The two cancers will kill more than 50,000 people this year.