The purpose of this study is learn the effect of gastric bypass surgery and sleeve gastrectomy on glucose metabolism mediated by neural and hormonal factors initiated after eating.

The purpose of this study is to determine the weight-independent effects of gastric bypass surgery and sleeve gastrectomy surgery on islet cell response after meal ingestion as mediated by hormonal and neural components of the gut. It will also address the differences between the two procedures.

Such information will be critical for the development of novel approaches for treatment of diabetes as well as improvement of glycemic effects of gastric bypass and sleeve gastrectomy in patients with partial diabetes remission or relapse after complete remission.

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