Surgery Or Lifestyle Intervention for Type 2 Diabetes (SOLID)

Inclusion Criteria: * Ages 18 to 65 years old. * Diagnosis of type 2 diabetes. * Individuals with a BMI of 30-40 kg/m2 * Approval for bariatric surgery (as confirmed by medical evaluation) * Insurance coverage for bariatric surgery * Willingness to change diet, physical activity and weight. * Ability to communicate with the investigator and be legally competent, provide written informed consent. Exclusion Criteria: * Diagnosis of type 1 diabetes, diagnosis of maturity-onset diabetes of the young (MODY), or latent autoimmune diabetes in adults (LADA) (all of which are associated with ß-cell destruction), daily insulin requirements \> 100 units, and poor preoperative glycemic control, as indicated by a HbA1c \> 6.5 - ≤ 8.5 or HbA1c \> 8.6 - \< 9.5 (individuals with this HbA1c value will require medical clearance and approval from the study physician). * Children and adolescents are not eligible to participate in the study. * Pregnant women (or those who intend to become pregnant during the study period) and women who are currently breastfeeding are not eligible to participate. * Use of medications known to significantly increase body weight, such as chronic systemic steroids or certain psychiatric medications (e.g., lithium tricyclic antidepressants and anti-psychotic agents). * Non-ambulatory individuals, defined as those who are unable to walk at least one city block without a cane or walker. * Any major illnesses that the surgical team believes present too great a risk for surgery. These include severe cardiac and pulmonary diseases, as well as uncontrolled type 2 diabetes. * Evidence of major depression or other psychiatric disorder (schizophrenia, bipolar disorder, major depression, bulimia nervosa, etc.) that is uncontrolled, poorly controlled, or, in the opinion of the Investigators, significantly interferes with daily living and functioning. * Any current (past 12 months) substance abuse or dependence disorder. * Participants with moderate anemia (Hgb \< 12 mg/dl for men and Hgb \< 11 mg/dl for women) * Conditions that may falsely elevate or decrease HbA1c values, including hemolytic or iron-deficiency anemia, hemoglobinopathies, and uremia. * Abnormal laboratory tests which are clinically significant per the investigator.