Lifestyle Intervention Study in Adjuvant Treatment of Early Breast Cancer

Inclusion Criteria:

* Post-menopausal woman with a diagnosis of invasive breast cancer (T1-3,pN0-2,M0) for which definitive surgery was performed during the previous 36 months.
* On adjuvant hormonal therapy with letrozole at time of randomization (either as initial adjuvant hormonal therapy or after a switch from tamoxifen or other hormonal therapy).
* BMI ≥ 24 kg/m2.
* Medical, surgical or radiation oncologist agrees to subject participation in a diet and physical activity program.

Exclusion Criteria:

* Life expectancy less than five years.
* Self-reported inability to walk at least 2 blocks (at any pace).
* Insulin requiring diabetes (telephone directed diet and physical activity changes would be difficult in this population without close coordination with the treating physician). Non-insulin requiring diabetics are eligible for the study.
* Serious digestive and/or absorptive problems, including inflammatory bowel disease and chronic diarrhea that preclude adherence to the study diet.
* Cardiovascular, respiratory or musculoskeletal disease or joint problems that preclude moderate physical activity. Moderate arthritis that does not preclude physical activity is not a reason for ineligibility.
* Psychiatric disorders or conditions that, in the opinion of the investigator, would preclude participation in the study intervention (e.g. untreated major depression or psychosis, substance abuse, severe personality disorder).
* Patients on aromatase inhibitors other than letrozole at study entry.
* Known recurrence of breast cancer (local, regional or distant) at any time prior to study entry.
* History of other malignancies except: adequately treated non-melanoma skin cancer, curatively treated in situ carcinoma of the cervix, or other solid tumours curatively treated with no evidence of disease for ≥ 5 years. Prior in situ cancer of the breast is not a reason for exclusion.
* Patients not fluent in either English or French (spoken and written).
* Patient unwilling or unable to provide informed consent.