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.

Once enrollment is complete (consent signed), participants will complete the baseline online medical history form and 9 questionnaires available online.

Baseline: Participants will come for an in-person visit to the GW School of Public Health and receive a Bluetooth-enabled digital scale and a Fitbit activity tracker. Research staff will help participants set up a study Fitbit and Looseit! account. Participants will undergo serum blood collection (10 ml) for HgbA1c and lipids. Participants will also be asked to bring in their infant, and the study team will measure the infant's weight and length. Participants will be asked to use this Fitbit and Looseit! account for the duration of the study to track their diet, activity, and weight. Study staff will access this data, review participant progress, and provide feedback as needed.

Start: All participants will begin with the DPP-based Lifestyle Intervention (LI). The program includes weekly online 45-minute Zoom group sessions for 4 weeks. After week 4, Zoom group sessions will be biweekly. The goal is a 2% weight loss at 4 weeks and a 3% weight loss at 6 weeks. These sessions will be led by a trained health counselor who is part of the research team. The health counselor will review the Fitbit Tracker information and provide tips for improving dietary intake and physical activity via email or text messaging based on the participant's preference.

At the end of week 4 and week 6, participants will submit their weight through Bluetooth-enabled scales.

If they have reached their weight loss goal, they will continue with the lifestyle intervention (LI) with online Zoom group sessions held every other week for the remainder of the intervention (for a total of a 6-month intervention).

After 4 or 6 weeks, participants who have not yet reached their weight loss goal (non-responders) will be randomly assigned to one of two intervention groups:

1. DPP-based Enhanced Lifestyle intervention (eLI)

   OR

2. Metformin (850 mg daily x 7 days, then 850 mg twice daily) orally

Enhanced Lifestyle Intervention (eLI): Participants will continue with the same components as the Lifestyle Intervention (LI), with the addition of guidance on healthy meal planning and online grocery shopping, including one free delivery per week. If randomized to this group, participants will continue to have group sessions every other week with others in the eLI arm of the study for the duration of the study (5 or 4.5 months, depending on when they were randomized to the Metformin arm) for a total of a 6-month intervention. Group sessions will last 45-60 minutes each. These sessions will be led by a trained health counselor in the research team. The health counselor will review the Fitbit Tracker and looseit! information and provide tips for improving dietary intake and physical activity via email or text messaging based on the participant's preference.

Metformin Arm: Participants in this arm will have an individual in-person session with the health counselor and study provider where they receive information about 1) the risks and benefits of Metformin for weight loss, 2) potential risks of infant hypoglycemia and the signs/symptoms of infant hypoglycemia, 3) risk factors for development of infant hypoglycemia and the potential long-term effects and consequences of infant hypoglycemia and, 4) guidance on how to take Metformin. After the in-person session, participants will visit the LabCorp facility on the GW Foggy Bottom campus to provide 5 mL of serum for creatinine and liver function testing, as well as undergo a urine pregnancy test. Participants with abnormal liver function tests (ALT outside 4-36 U/L or AST outside 8-33 U/L), eGFR < 60 ml/min, or a positive pregnancy test will be ineligible for Metformin. Once lab results are reviewed, participants will be placed on Metformin by mouth (850 mg daily x 7 days, then 850 mg twice daily). Tablets will be distributed by the Investigational Drug Pharmacy at the George Washington School of Medicine and Health Sciences. This is the current dosage prescribed for weight loss in the clinical setting.

Participants on Metformin will have a 15-minute follow-up call one week after starting the medication to answer additional questions, assess for any medication side effects, and assess for adherence, and then 15-minute follow-up calls by the research team every 2 weeks. Participants will be educated that it is safe to continue to breastfeed while on Metformin, as recommended by the American College of Obstetricians and Gynecologists published recommendations on postpartum care following a pregnancy with GDM. There are no group sessions for this group. Participants will be encouraged to continue practicing healthy lifestyle behaviors learned during the first 4 weeks of the intervention.

End of study: At the end of the study (6 months), participants will complete one questionnaire with updates about their health since their baseline questionnaire and will also complete 9 online questionnaires (same as baseline). Participants will come for an in-person visit where they will be asked to bring their pill container, if they were randomized to the Metformin arm, and provide a 10 ml serum sample for HbA1c, and lipids via LabCorp. Participants will also be asked to bring in their infant, and the study team will measure the infant's weight and length.

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.

The research team will share unidentified results of outcomes, including clinical and behavioral outcomes.

9 months following close of the study.

Based on a formal request to the principal investigator.