Sleeve Gastrectomy (also known as Tube Stomach Surgery) is a bariatric surgical procedure that involves the permanent surgical removal of a large portion of the stomach, transforming it into a tube-shaped structure. This operation significantly reduces the stomach's volume by making it a natural extension of the esophagus.

While organs in the digestive system such as the esophagus and intestines are naturally tube-shaped, the stomach is typically pouch-shaped to store food. In Sleeve Gastrectomy, the large, pouch-shaped part of the stomach is removed, and the remaining section forms a thin, tube-like structure that continues the digestive tract. No foreign objects are inserted into the stomach during this procedure; the term "tube stomach" refers to the stomach's new shape.

The effect of the surgery is not limited solely to reducing the physical volume of the stomach. It also leads to a significant decrease in the levels of the hunger hormone (ghrelin) secreted from the removed portion of the stomach. This hormonal change helps patients experience reduced appetite and less hunger, supporting weight loss. Thus, Sleeve Gastrectomy contributes to weight management through both mechanical volume restriction and significant hormonal effects.