The pouch initially holds about 1 ounce of food and expands to 2 to 3 ounces with time. The small outlet delays the emptying of food from the pouch and causes a feeling of fullness. After an operation, the person usually can eat only one-half to 1 cup of food without discomfort or nausea. Also, food has to be well chewed. Most people who have a restriction operation lose the ability to eat a large amount of food at one time.
Some patients do return to eating modest amounts of food, without feeling hungry.
Restriction operations for obesity include gastric banding and vertical-banded gastroplasty. Both operations serve only to restrict food intake. They do not interfere with the normal digestive and absorptive processes. These operations combine the creation of small stomach pouches to restrict food intake and the construction of bypasses of the duodenum and other segments of the small intestine to reduce nutrient absorption. This operation is the most common gastric bypass procedure.