An Endometrial Cancer Chemoprevention Study of Metformin

"Participants gradually increase the dose of metformin by mouth as listed below:~Week 1: One capsule each day Week 2: One capsule 2 times each day Week 3: One capsule 3 times each day Week 4: Two capsules 2 times each day~After week 4, participant continues to take 2 capsules of metformin 2 times each day.~Each capsule is 425 mg."

Placebo taken by mouth twice daily for 4, 30 day cycles.

Endometrial biopsies obtained at baseline and after 4 months.

Lifestyle intervention consists of 16 in-person sessions offered over a 4 month period.

Completion of questionnaires about diet and exercise at baseline, during treatment and at end of study. Questionnaires take about 30-40 minutes to complete.