The stomach is stapled and the outer 80% is removed. The intestines are re-plumbed so that food passes from the stomach into the distal part of the small intestine (further down than with a gastric bypass).
The surgery works by altering gut signals that regulate appetite, taste and blood sugar. In addition, the stomach size is reduced and the absorption of fats and nutrients is reduced.
On average, people lose 30-40% of their total body weight. This operation carries the greatest risk of nutritional deficiencies and the sleeve component is irreversible.
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