What is the primary mechanism of action of gastric bypass surgery?

The primary mechanism of action of gastric bypass surgery involves both restrictive and mal-absorptive components. The restrictive aspect occurs because the surgery creates a small stomach pouch, which limits the amount of food that can be consumed at one time. This restriction helps patients feel fuller after eating smaller portions.

In addition to this restrictive mechanism, gastric bypass also introduces a malabsorptive component. The surgical procedure reroutes a portion of the small intestine, which leads to a reduction in the absorption of calories and nutrients as food passes through a shorter length of the small intestine. This combined approach of restricting food intake while also reducing nutrient absorption plays a crucial role in the significant weight loss and metabolic changes observed in patients post-surgery.

The option focused solely on restrictive mechanisms would not encompass the full-effectiveness of the surgery, while the mal-absorptive-only option would ignore the critical role that restriction plays in patient outcomes. Ghrelin modulation, although potentially impacted by the surgery, is not the primary mechanism of action but rather a secondary effect related to appetite regulation post-surgery.