Hi, Omeprazole belongs to the group of medications known as proton pump inhibitor (PPI) medications which is used to reduce the amount of acid the stomach makes. It is widely used treatment for indigestion, heartburn, acid reflux, stomach ulcers, Zollinger-Ellision syndrome etc. Recent studies have clearly demonstrated that PPI therapy contributed significantly to body weight changes in patients acid reflux by relieving the adverse symptoms rather than altering the state of gastric emptying. Untreated patients suffering from reflux symptom of find it difficult to have large meals, because this generally aggravates their symptoms. Untreated patients may therefore reduce their meal sizes. It is conceivable, therefore, that the resolution of reflux symptoms by PPI like omeprazole treatment leads to a higher food intake resulting in body weight gain. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician