Inclusion Criteria:

• * completed active treatment for a Stage 0-III breast cancer diagnosis within 6 months to 5 years of enrollment.
• * obese as defined by a body mass index (BMI) of 30 to 50 kg/m2
• * patients who are on adjuvant endocrine therapy will be allowed to participate.
• * sedentary (participating in less than 90 min of moderate intensity activity per week) and have at least one limitation in activity on the 10-question RAND-36 Physical Function Subscale to ensure some exercise intolerance

Exclusion Criteria:

• * functional limitations that make independent exercise unsafe
• * current smokers
• * metastatic breast cancer
• * ongoing or active infection with recent antibiotics or steroids
• * heart disease precluding exercise (congestive heart failure, unstable angina pectoris, cardiac arrhythmia)
• * psychiatric illness/social situations that would limit compliance with study requirements
• * orthopedic or neuromuscular disorders or arthritis that preclude participation in exercise
• * unwilling or unable to follow protocol requirements
• * pregnant or nursing
• * any condition which in the investigator's opinion deems the subject an unsuitable candidate to participate in this study
• * presence of provokable ECG changes suggestive of heart disease, or dangerous arrhythmias or exercise induced hypertension, etc. during the cardiopulmonary exercise test
• * non-English speaking