 We plan to study 20 healthy subjects on 4 occasions where they will receive ghrelin, ghrelinEx-9, Ex-9 or saline infusion after an overnight fast in a randomized order; Ex-9 will be used to block GLP-1 action. A 240-minute meal tolerance test MTT using a dual glucose tracer method will serve as the foundation of each study visit. One tracer, 6,6-2H2glucose will be infused intravenously before and during the test meal to quantify fasting endogenous glucose production EGP, and glucose disappearance during the meal. A second tracer, U-13Cglucose, will be included in the meal to trace the appearance of oral glucose. The systemic appearance rates of both ingested tracer and total i.e., ingested and endogenously produced glucose will be calculated. Using this protocol, we will be able to evaluate a insulin secretion in response to mixed-meal ingestion, b glucose appearance and glucose disappearance during meal ingestion, c the ghrelin effect on these parameters without GLP-1, and d the effect of GLP-1 in the response based on the effects with and without Ex-9. 