Effectiveness Study of a Lifestyle Intervention Versus Metformin in Mothers With Recent Gestational Diabetes

The goal of this clinical trial is to evaluate the effectiveness of a 6-month lifestyle intervention compared to Metformin in postpartum women who have delivered a singleton, live born infant within the last 12 weeks to 1 year and had a pregnancy complicated by gestational diabetes. The main question this study aims to answer is: Is a Lifestyle Intervention or Metformin more effective for weight loss in postpartum women with recent gestational diabetes? Researchers will compare a 6-month Lifestyle Intervention and Metformin to see if either intervention is more effective in achieving weight loss and improving health outcomes. Participants will: * Attend an in-person baseline visit to receive a Bluetooth-enabled scale and Fitbit, have blood drawn for testing, and have their height, weight, and blood pressure measured. Participants will also be asked to bring in their infant, and the study team will measure the infant's weight and length. * Track diet, physical activity, and weight using the Fitbit and Looseit! apps. * Attend weekly online group sessions for the first 4 weeks, then biweekly sessions. * If not meeting weight loss goals, be randomized to either Enhanced Lifestyle Intervention or Metformin arms of the study. * If randomized to Metformin, participants will attend one in-person meeting with the study provider, get blood drawn for testing, and undergo a urine pregnancy test before starting the medication. * Continue with biweekly group sessions or have regular check-in calls. * If randomized to the Enhanced Lifestyle Intervention, participants will get a free Instacart membership, a 1:1 session with the study health counselor focused on meal planning and free grocery delivery once a week for the remainder of the study. * Participants will meet every other week via Zoom with the health counselor and other participants in the enhanced lifestyle arm. * At the end of the 6 months, all participants will come for an in-person visit to get blood drawn for testing. Participants will also be asked to bring in their infant, and the study team will measure the infant's weight and length.