The gastric bypass largely works through reduced food intake (restriction). This is achieved in several ways.

• Quick feeling of fullness: the small stomach pouch causes an early feeling of fullness, which inhibits the intake of food.
• Reduced feeling of hunger: the feeling of hunger reduces appreciably. This can be explained by the fact that the stomach pouch is separated from the stomach, as a result of which less of the hunger hormone (grhelin) is produced.
• Dumping syndrome: this is an uncomfortable feeling, which is stimulated by the food in the small stomach pouch going directly to the small intestine. This feeling tends to be caused by eating sugars and by eating too quickly. Dumping stops a lot of patients from eating sweets, which is one of the reasons for weight gain after purely restrictive operations, such as gastric banding and gastroplasty. This dumping syndrome differs from patient to patient and appears to increase in the years after surgery