At the beginning of each study date as well as at the time of the test meal several blood samples will be taken to evaluate blood glucose and blood glucose-influencing parameters (insulin / C-peptide, intestinal hormones, inflammatory parameters such as C-reactive protein, IL1beta and IL1-receptor agonist as well as macrophage and t-lymphocyte subpopulations) will be controlled. Questionnaires for dumping symptoms (Dumping Rating scale, Sigstad Score) and hypoglycemia testing with mini-mental test, stanford sleepiness scale and Edinburgh Hypoglycemia Scale will be performed repetitively.