"Colon cancer patients who followed the American Cancer Society guidelines on nutrition and physical activity had a marked reduction in risk of death and recurrence," lead author Erin Van Blarigan of the University of California at San Francisco said in a telephone interview.

"The magnitude of benefit was on par with what you might expect from an invasive treatment, if not larger."

The ACS first released Nutrition and Physical Activity Guidelines for Cancer Survivors in 2001, the study authors note in the journal JAMA Oncology, April 12. Healthy people who follow these guidelines may reduce their cancer risk, they add, and adhering to the guidelines has been linked to a better quality of life in colon cancer survivors.

To investigate whether ACS guideline adherence might extend colon cancer survival, the authors looked at 992 people participating in a clinical trial of treatment for advanced colon cancer who reported on their diet and physical activity during and after chemotherapy.

Each person was assigned a score from 0 to 6 based on their adherence to the ACS guidelines, which included recommended ranges for body mass index (BMI), physical activity, and consumption of vegetables, fruit, whole and refined grains and red or processed meat.

During an average seven years of follow-up, 335 patients had recurrence of their cancer and 299 died, including 256 who died from cancer recurrence. Twenty-six percent of the study participants had an ACS guideline score of 0-1, while only 9 percent scored 5 to 6.

Patients who followed the guidelines most closely were 42 percent less likely to die during follow up than those with the worst adherence, and had better disease-free and recurrence-free survival. Overall, the authors found, people who adhered well to the guidelines were 9 percent more likely to survive for five years after diagnosis than those with worse adherence.

Patients who logged 150 minutes or more of moderate physical activity each week, such as brisk walking; ate at least five servings of fruits and vegetables a day; and chose whole over refined grains lived longer and were less likely to have cancer recurrence, the study found. Those with BMIs of 23 to 29.9, somewhat higher than the ACS guidelines recommend, also had improved survival compared to those with higher BMIs.

Low-to-moderate consumption of alcohol (no more than one drink a day for women, two a day for men) was not associated with worse survival or disease recurrence, but heavier drinking was.

Eating more red and processed meat was not associated with survival or cancer recurrence. Paying attention to carbs appears more important for colon cancer survivors, Van Blarigan noted, because sugar-sweetened drinks, foods with a high glycemic load and other less-healthy carbs have been linked to worse outcomes.

"The question is, if you added those types of recommendations (avoiding sugar-sweetened beverages, etc.) to the general guidelines would they have an even bigger benefit," she said.

Making lifestyle changes is "a big challenge," she added, noting that research has shown that advice from their oncologist is the most powerful motivator for cancer survivors.

The research team is also investigating strategies for supporting cancer survivors in building healthier habits, including apps, websites and text messaging. "So far it seems that people do like these tools and find them useful so it is encouraging, but whether it's going to be effective at changing behavior we don't know yet," Van Blarigan said.

The new study is especially valuable because it yields specifics that doctors can discuss with colorectal cancer survivors, said Dr. Michael J. Fisch of AIM Specialty Health in Chicago, who co-wrote an editorial accompanying the study.

Strategies for supporting people in following healthier lifestyles also need to include improving access to affordable, healthy foods and opportunities for physical activity, he said in a telephone interview.