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

Inclusion Criteria: * Mothers between 8 weeks and 12 months postpartum from a pregnancy complicated by GDM will be recruited. The research team will begin recruiting women who are at least 8 weeks postpartum to provide time to describe the study and answer any questions. Mothers who want to participate will be enrolled in the study between 12 weeks and 12 months postpartum. * BMI of 25 kg/m2 to 45 kg/m2 * Singleton delivery * Participants must also have a working cell phone, be willing to accept email or text messages attend Zoom calls, and be willing to be potentially randomized to drug therapy with Metformin. Exclusion Criteria: * Pregnant or planned pregnancy within the next 6 months. * Participation in any other weight loss program or taking weight loss medication. * Normal or underweight BMI (BMI \< 24.9 kg/m2) * Multi-fetal (twins or triplets) gestation * Women with type 1 or type 2 diabetes, malignancy, other serious co-morbidities (advanced kidney disease, NYHA class 3-4 CHF, advanced COPD), schizophrenia or other major psychiatric disease, and substance abuse or AIDS. * Women whose infants have significant medical conditions, such as congenital heart disease, renal impairment, or hepatic impairment.