The Effects of Bariatric Surgeries on Glucose Metabolism

Inclusion Criteria: * Hypoglycemic RYGB patients with documented blood glucose level \<50 mg/dl * Asymptomatic individuals with bariatric surgery * Healthy non-surgical patients with no personal history of diabetes * Subjects must physically be able to come to our clinical research center Cedars-Sinai Medical Center Exclusion Criteria: * Active heart, lung, liver, gastrointestinal or kidney disease; unable to give informed consent; pregnancy; uncontrolled high blood pressure or high cholesterol; significant anemia (hemoglobin \<11g/dL); prisoners or institutionalized individuals; type 2 diabetes mellitis; development of any serious medical or psychiatric illness during recruitment or studies; * RYGB patients will be disqualified if they have gastric outlet obstruction or severe diarrhea. * Healthy non-surgical patients with personal history of diabetes For administration of atropine, the following exclusions also apply: * History of glaucoma * Uncontrolled hypertension (any subjects with BP\>140/90 and history of dyslipidemia * Taking any medication that might interact with atropine and cannot be stopped will be excluded from the study) * Myasthenia gravis * Brain pathology * Enlarged prostate in men