A Randomized Pilot Study to Evaluate the Effects of a Short Course of Metformin Versus No Therapy in the Period Prior to Hysterectomy for Grade 1-2 Adenocarcinoma of the Endometrium in Obese Non-Diabetic Women

Inclusion Criteria: * Histological confirmed diagnosis of grade I or II adenocarcinoma of the endometrium * Must be obese as defined by a body mass index (BMI) greater than or equal to 30 kg/m2 * Candidate for surgical removal of their uterus as part of their endometrial cancer treatment * Subjects must have signed informed consent * Age 42 - 65 years of age * Electrocorticogram (ECOG) Performance status of 0 - 2 * History of adequate renal, liver, and bone marrow function: * Hb: (adequate for surgical intervention, with transfusion if necessary) White Blood Cell (WBC): (normal range) * Platelets: (180K/cmm) * Liver Function Test(LFTs): Normal bilirubin (\<2.0mg/dL), AST/ALT (2xULN) * Renal function: creatinine less than 1.4 * Female subjects must either not be of child-bearing potential or must have a negative urine pregnancy test within 7 days of randomization to Metformin. Subjects are considered not of child-bearing potential if they are surgically sterile or they are postmenopausal for greater than 12 months. Exclusion Criteria: * Poorly differentiated cancer or any of the high-risk subtypes of endometrial cancer including serous, clear cell, or carcinosarcoma * History of diabetes mellitus Type 1 or Type 2. * Receiving metformin prior to enrollment * Known hypersensitivity to metformin. * Unable to swallow and retain oral medication. * Pregnant or lactating. * Previous or concurrent malignancies, except non-melanoma skin cancers, unless curatively treated and with no evidence of recurrence for \> 5 years * If the physician feels that the candidate is not suitable for the study, he/she will be excluded. * Currently taking biguanides, sulfonylurea drugs, thiazolidinediones, insulin, or mTOR or DPP-4 inhibitors or having taken any of these medications during the 12 weeks prior to study participation. * Clinical symptoms of gastrointestinal obstruction or bleeding and consideration for immediate surgery or immediate neoadjuvant chemoradiation. * History of lactic or other metabolic acidosis. * Uncontrolled infectious disease. * History of positivity for human immunodeficiency virus (HIV). * History of congestive heart failure requiring pharmacologic treatment. * History of excessive alcohol abuse, defined by a habitual intake of more than three drinks daily. * Mal-absorption syndrome, disease affecting gastrointestinal function, or previous resection of the stomach or small bowel. * Current use of medications for weight loss. * Currently taking cimetidine, thiazide diuretics or cephalexin. If a patient needs some of these agents, alternative agents should be substituted.