The objective of this study is to examine gastric emptying and satiety hormones after oral glucose stimulation in 2 different concentrations in morbidly obese patients after Roux-en-Y-gastric-Bypass.

After gastric bypass many patients suffer from early and/or late dumping syndrome as a reaction to carbohydrate rich meals. Gastric emptying after bypass is accelerated and nutrition enters the intestine faster, which leads to osmotically driven fluid shifts from the blood to the lumen. Late dumping occurs 1-3 h after eating, and is caused by hyperinsulinemia and is therefore characterized by symptoms of hypoglycemia like weakness, sweating, and dizziness. Many people have both types. In most studies examining satiety hormones after oral glucose stimulation in non-operated patients, glucose loads of 50-75g are used. For a measurable GLP-1 rise a threshold of 2 kcal/min. at the intestine is needed. After gastric bypass gastric emptying is accelerated and less glucose is necessary to reach this threshold. The "threshold load" and "tolerable load without dumping symptoms" is not yet know.

Inclusion Criteria:

• 6 weeks post gastric bypass surgery,
• non-diabetic patient

Exclusion Criteria:

• smoker,
• diabetes,
• gastrointestinal motility disorder,
• medication influencing gastric emptying