EXERT-BC Protein: Protein Supplementation to Improve Body Composition After Treatment for Breast Cancer

Inclusion Criteria: 1. Age 20-89 years 2. Women prescribed exercise as a SOC 3. Women with a biopsy proven diagnosis of ductal carcinoma in situ (DCIS) or invasive carcinoma of the breast 4. Women must have undergone treatment for breast cancer, including one or more of the following: surgery, radiation therapy, chemotherapy, immunotherapy, or hormonal therapy. Women undergoing active chemotherapy are not allowed on study. Immunotherapy or targeted agent usage is allowed. 5. Women with \> 3 months of resistance training experience under expert guidance by a CSCS 6. Must be able to read and understand English and consent for themselves. Exclusion Criteria: 1. Any current treatment with cytotoxic chemotherapy for breast cancer 2. Inability to safely engage in group sessions of resistance training as deemed by study PI 3. Severe arthritic, joint, cardiovascular, or musculoskeletal condition deemed by PI to be unsafe to engage in resistance training 4. Beta blocker or GLP-1 inhibitor medications 5. Pregnant women 6. Males 7. Lactose intolerance 8. Cow's milk or whey protein allergy