A Study of the Body's Response to Exercise and a Plant-Based Diet in Overweight Postmenopausal Women With Breast Cancer

Inclusion Criteria: * Patients with histologically-confirmed, HR-positive (ER and/or PR) stage 1-3 breast cancer * Completed anti-HER2 therapy, if HER2-positive * Postmenopausal status defined by lack of menses for 2 years, oophorectomy, or medical ovarian suppression * At least 3 months post completion of chemotherapy, if administered * At least 3 months post radiation, if administered * Receiving adjuvant endocrine therapy with an aromatase inhibitor (anastrozole, letrozole, exemestane) * ECOG performance status of 0 to 1 * Sedentary (i.e.,performing \<150 minutes / week of exercise structured moderate-intensity or strenuous-intensity) * Age ≥ 18 * BMI ≥ 27 * Able to achieve an acceptable peak baseline CPET, as defined by any of the following criteria and in the absence of high risk ECG findings or other inappropriate response to exercise as determined by the investigator: * Achieved a plateau in oxygen consumption, concurrent with an increase in power output * A respiratory exchange ratio ≥ 1.10 * Attainment of maximal predicted heart rate (HRmax) (i.e., within10 bpm of age- predicted HRmax \[HRmax= 220 - Age (years)\] * Volitional exhaustion, as measured by a rating of perceived exertion (RPE) ≥ 18 on the BORG scale. * Willingness to comply with all study-related procedures * Intact breast available for biopsy Exclusion Criteria: * Presence of metastatic disease * Any concurrent malignancy requiring active treatment with the exception of selective estrogen receptor modulators and aromatase inhibitors * Insulin-dependent diabetes mellitus or non-insulin dependent diabetes mellitus on insulin therapy * Enrollment onto any other interventional investigational study except interventions determined by the PI not to confound the effect of exercise or diet on study outcomes * Mental impairment leading to inability to cooperate * Any of the following contraindications to exercise: 1. Acute myocardial infarction within 3-5 days of any planned study procedures; 2. Unstable angina 3. Uncontrolled arrhythmia causing symptoms or hemodynamic compromise 4. Recurrent syncope 5. Active endocarditis 6. Acute myocarditis or pericarditis 7. Symptomatic severe aortic stenosis 8. Uncontrolled heart failure 9. Acute pulmonary embolus or pulmonary infarction within 3 months of any planned study procedures 10. Thrombosis of lower extremities 11. Suspected dissecting aneurysm 12. Uncontrolled asthma 13. Pulmonary edema 14. Respiratory failure 15. Acute non-cardiopulmonary disorders that may affect exercise performance * Any other condition or intercurrent illness that, in the opinion of the investigator, makes the subject a poor candidate for study participation. * Nut or legume allergy * Concurrent participation in weight loss programs