Effect of Weight Loss on Breast Density Using Digital Mammography and MRI in Women Who Are At Increased Risk For Breast Cancer

Inclusion Criteria: * Women eligible for gastric bypass surgery * Pre-menopausal women * All women will have signed an informed consent form prior to participating in study procedures Exclusion Criteria: * Women with a history of breast cancer * Women currently taking exogenous hormone replacement therapy * Women currently taking a SERM * Women currently taking an aromatase inhibitor * Pregnant or lactating women * Women who have been pregnant or lactating in the past 2 years * Women who have metallic or other surgical implants * All subjects will have a determination of their estimated glomerular filtration rate (eGFR) within 24 hours of undergoing any study where gadolinium based contrast agents will be administered * Subjects should not have a known history of recent onset acute renal dysfunction * Subjects with a history of stable chronic renal dysfunction may participate in studies using GBCA based on their eGFR, as outlined below * Subjects should not have severe liver dysfunction, particularly when associated with kidney disease * Subjects should receive GBCAs in the perioperative period (i.e. within 4 weeks) after renal or liver transplantation