Clinical Research Directory

Inclusion Criteria: * Age between 18 and 65 years; * RYGB or SG as primary bariatric surgery; * A 2 year post-operative period without significant peri-operative or postoperative complications that could affect oesophageal transit, GE, or weight loss; * "Normal" weight loss, according to our expectations (25% \< TWL \< 35%); * Participants must be able to adhere to the study visit schedule and protocol requirements; * Participants must be able to give informed consent (IC) prior to any study procedures; * Willing to be informed about incidental findings of pathology and approving of reporting this to their general physician. Exclusion Criteria: * Pre-existent oesophageal or gastric motility disorders, dysphagia, reflux, dumping syndrome, (postprandial) abdominal pain, neurological or metabolic conditions that significantly affect oesophageal or gastric motility; * When using proton pump inhibitors (PPI) or H2-antagonists, the inability to stop using them for 3 days; * Using opioids; * Previous oesophago-gastric surgery, other than bariatric surgery; * Unable to stop smoking for 24h; * Pregnancy or breast-feeding; * Patients with a drug or alcohol addiction; * Gluten intolerance; * Intolerance to tracer ingredients; * Participating in another scientific study at the same time, if this study interferes with the current study in any way.