In addition to metformin, all participants will be given lifestyle modification (LSM) education on diet and physical activity, followed by guidance on how to adhere to the LSM, depending on random assignment to intervention group (education only (n=26) vs. implementation intentions alone (n=27) vs. implementation intentions with partner (n=27)). The LSM coaching for different intervention groups will allow the investigators to test whether there are more effective ways for adherence than others. Participants in these three LSM intervention groups will be further randomized to either Metformin (n=40) or Placebo (n=40), such that participants in the three LSM groups will be randomly and evenly distributed across the two study medication groups.