Bariatric Surgery
Ebariatric Surgery

Digestive Changes After Bariatric Surgery

Major weight loss surgeries have a tremendous impact on your digestive tract. Whatever type of bariatric surgery you are considering, the major organs of the digestive tract: the stomach, small intestines, and in some cases, the duodenum, are surgically altered, causing major changes to your digestive system. Bariatric surgery interferes with digestion because of the alterations performed to the stomach and small intestine. These changes are what trigger weight loss.

Less food intake

Bariatric surgery shrinks the size of the stomach, causing you to eat less. The stomach is made smaller using different methods in each type of bariatric surgery.

Gastric bypass

In gastric bypass surgeries, the stomach is made smaller and is bypassed by the rest of the small intestine; therefore, food travels much more quickly into the lower part of the small intestine. Calories and nutrients in food are restricted, leaving only a small amount to be absorbed by the body, causing dramatic weight loss.

More about gastric bypass, including Roux-en-Y, BDP, and duodenal switch

Digestive Changes After Bariatric Surgery

Adjustable gastric banding

In gastric banding surgeries, the band around the stomach controls the stomach outlet (stoma) between the lower and upper parts of the stomach due to the narrow passage. This restriction creates a full feeling for the patient because food is moving much more slowly through the narrow stomach passage.

More about adjustable gastric banding, LAP-BAND®, and REALIZE Band™

Digestive Changes After Bariatric Surgery

How much food can I eat?

The stomach is greatly reduced in size-by about 90 percent. Its capacity to hold food is about the size of three - four tablespoons. The quantity of food that you eat is greatly reduced.

Hormonal changes

Ghrelin is a hormone that stimulates hunger. Ghrelin is produced by the fundus, or lower portion, of the stomach. Patients who undergo gastric bypass surgery experience an immediate and significant drop in ghrelin production. The gherlin reduction is caused by the food bypassing the fundus and therefore not stimulating the cells that produce this appetite-stimulating hormone. Gastric bypass is the only bariatric surgery that reduces gherlin production ( Frühbeck).

Risks of bariatric surgery

For an overview of the risks and complications that can accompany bariatric surgery, please see Risks of Bariatric Surgery.

Find out more about bariatric surgery

For more information on bariatric surgery, browse the menu options above. To find a bariatric surgeon near you, use our bariatric surgeon locator.

Find out if you are a candidate for bariatric surgery.


Frühbeck, G, Caballero, A, Gil, M. 2004. "Fundus Functionality and Ghrelin Concentrations after Bariatric Surgery." New England Journal of Medicine. January 15. (350;3):308-309. Pamplona, Spain: University of Navarra. (accessed July 12, 2009).

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