Published in the Journal of Clinical Oncology, this is the first study to look at the impact of a combination of both healthy diet and physical activity on breast cancer survival.
"We demonstrate in this study of breast cancer survivors that even if a woman is overweight, if she eats at least five servings of vegetables and fruits a day and walks briskly for 30 minutes, six days a week, her risk of death from her disease goes down by 50 per cent," said the paper's first author, Dr. John Pierce, Director of the Cancer Prevention and Control Program at the Moores UCSD Cancer Center.
"The key is that you must do both," he added.
The researchers studied 1,490 women with early stage breast cancer, aged 50 years on average. The subjects were randomly assigned to the non-intensive dietary arm of the ongoing Women's Health Eating and Living (WHEL) study, a multi-centre study based at UCSD, investigating the effect of a plant-based diet on additional breast cancer events.
At the time of enrolment in the study, the women were assessed for their dietary pattern and physical activity. The researchers followed them for between five and 11 years.
It was found that only 16 per cent of obese women were both physically active and had a healthy diet, compared to 30 per cent in the rest of the study population. The researchers noted that women who were both physically active and had a healthy diet were much more likely to survive through the follow-up period than the rest of the study group.
The mortality rate of such women was seven per cent, approximately half of that seen for the rest of the study population.
"Of particular importance is that this halving of risk was seen in women who were not obese as well as in those who were obese," said Dr. Cheryl Rock of the Center's Cancer Prevention and Control Program.
"Also, the effect was not seen in women who practiced only one of the lifestyle patterns - high vegetable and fruit intake, or physical activity," added the co-author.
Now that their longitudinal study has furnished significant results, the researchers want to further study the combined protective effect of diet and physical activity on breast cancer survival in an interventional study, wherein they will change the diet and level of physical activity in breast cancer survivors.