The longitudinal study from the Moores Cancer Center at the University of California, San Diego, looked at 1,490 women aged 70 years and younger -- average 50 years -- with early stage breast cancer who were randomly assigned to the non-intensive dietary arm of the ongoing Women's Health Eating and Living study.

The study, published in the Journal of Clinical Oncology, found 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 percent.

Those 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, according to first author John Pierce, director of the Cancer Prevention and Control Program at the Moores University of California, San Diego, Cancer Center.

"The key is that you must do both," Pierce said in a statement.