Additional Study Information: We're conducting a research study on how much insulin is needed to control blood sugar in people who are made temporarily resistant to insulin's effects. Insulin is the main hormone (chemical signal) that the body uses to lower the levels of sugar in the blood. We are interested in looking at insulin levels because we think that lowering insulin levels may be a way to treat people with excessive fat in their liver (called "fatty liver disease"). Before we look at liver fat, though, we need to know how lowering insulin levels affects blood sugar. We're seeking adult volunteers, aged 18-65, who are overweight or obese with a body mass index of 25.0-39.9 but have not been diagnosed with prediabetes or diabetes. Participants will undergo two pancreatic clamp procedures separated by 2-4 weeks after being made temporarily insulin resistant by taking a steroid pill called dexamethasone for 2 days. 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 insulin, over about 7 hours. Participants will be required to stay in the hospital overnight before the clamp. We'll 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 while someone is temporarily resistant to insulin's effects. In one of the clamps, we'll lower the level of insulin incrementally, while in the other we will keep it the same throughout. The order that you would go through the two different clamps would be at random (like tossing a coin). Participants will attend an outpatient screening visit plus two inpatient visits of up to 30 hours each, and will be compensated up to a total stipend (salary) of $850 plus additional reimbursement for travel expenses.