Eating sugar or high-fat food after gastric bypass surgery can cause dumping syndrome. In this syndrome, food high in sugar and fat enters and moves speedily from the stomach into the small intestine. If a large amount of food enters the small intestine quickly, causing vomiting, nausea, dizziness, sweating, and diarrhea. High-fat or high-sugar food on consumption causes nausea and vomiting after meals.