Effects of Activity on Diabetes Risk Among Breast Cancer Survivors on Endocrine Therapy (ABIDE)

Inclusion Criteria: * Female * diagnosed with breast cancer * age 18-80 years * Completed surgery, chemo- and/or radiation therapy * Prescribed aromatase inhibitor or SERM for at least one year from the time of screening Exclusion Criteria: * Age \< 18 or \> 80 * Type 1 diabetes * Type 2 diabetes * Prescribed anti-hyperglycemic medication, insulin, or sulfonylurea. * Pregnant, breastfeeding or planning to become pregnant in next 2 months * Have absolute contraindications to exercise testing which are: 1. Unstable angina 2. Recent myocardial infarction, cardiac surgery, or vascular surgery (\<3 months) 3. Uncontrolled high blood pressure 4. Heart failure 5. Peripheral artery disease (based on report of symptomatic claudication) 6. Hepatic or renal disease 7. Severe arthritis or mobility impairment that would interfere with exercise testing * Suspected cognitive impairment that would prevent understanding or comprehension of study procedures.