Additional Study Information: We are conducting a research study on how much insulin is needed to control blood sugar in people at risk for type 2 diabetes. We are seeking adult volunteers, aged 18-65, who are overweight or obese with a body mass index of 25-45 and have been diagnosed with or are at risk for prediabetes. Participants will undergo two pancreatic clamp procedures separated by 2-8 weeks. A pancreatic clamp is a technique in which we temporarily shut off the body's production of insulin with intravenous (into the vein) hormone mixtures that allow researchers to vary levels of the blood sugar-lowering hormone, insulin, over about 7 hours. Participants will be required to stay overnight. We will perform blood tests during the procedure to look at levels of glucose (sugar), insulin, and certain fats. The goal is to see how lowering the insulin level by different amounts affects blood sugar levels. Participants will attend two outpatient screening visits, two inpatient visits of up to 30 hours, and will be compensated up to a total stipend (salary) of $1000 plus additional reimbursement for travel expenses.