The effect of inhibiting the parasympathetic nervous system on insulin, glucagon, and glucose will be examined in normal weight and obese men and women. Furthermore, the importance of early insulin release will be examined. Each subject will undergo 4 treatments: 1) saline infusion, 2) brief infusion 3) atropine infusion and 4) atropine and insulin infusion. During each of the treatments, subjects will ingest a mixed meal containing 600 kcal and will undergo a blood sampling protocol in which arterialized venous blood samples will be drawn over a 4 hour period of time.