The study team will invite participants with prediabetes or mild diabetes (HbA1c 5.7-7.0) to join a 5-year research study that will define subphenotypes of type 2 diabetes based on underlying physiology (eg insulin resistance, beta-cell dysfunction, incretin defect, liver insulin resistance) and then test the hypothesis that response to three first-line treatments will vary according to metabolic subphenotype. Variables of interest include glucose, cardiovascular risk markers, and weight. Treatments include Mediterranean diet, metformin, and a GLP-1 agonist. Participants will go through an initial screening, followed by three treatment periods, each lasting 4 months with 3 month washout in-between treatment periods. This study will help us understand how personalized treatments can help control blood glucose, reduce cardiovascular risk, and manage weight. While there may be minor side effects-like slight discomfort from blood tests, gastrointestinal symptoms from some of the medications, and small radiation exposure from DXA body scans-the treatments offered in this study have all been well studied and are known to lower risk for diabetes and cardiovascular disease