Exercise and Metformin in Colorectal and Breast Cancer Survivors

Subjects will be randomized into one of four groups: exercise training, exercise training and metformin, metformin alone, or control arm. All subjects will have lifestyle measurements, interviews regarding activity level, diet questionnaires, and blood tests. Subjects randomized to exercise training will participate in two supervised exercise sessions per week with an exercise physiologist for 3 months. They will also be asked to exercise on their own for up to an additional 120 minutes each week. Subjects randomized to exercise training and metformin will participate in two supervised exercise sessions per week and will take metformin. Metformin will be taken once daily for the first two weeks and then twice daily for 3 months. Subjects randomized to metformin will take metformin once daily for the first two weeks and then twice daily. Subjects on the control arm will receive a packet of educational information on nutrition and physical activity developed by the National Cancer Institute and American Cancer Society. In addition to education information, they will be offered two supervised sessions with an exercise physiologist as well as a pedometer 3 months after enrollment in the study.