pouch size stomach stretch after bariatric surgery

Does Pouch Size Matter & Will the Stomach Stretch After Bariatric Surgery?

March 5, 2018

The Misconception of a WLS Pouch

A big misconception in bariatric surgery from the general public is the idea that surgery works in a mechanical fashion, meaning a small WLS pouch or a small sleeve of a stomach is responsible for the individual to eat less and lose weight. The most fascinating thing about bariatric or metabolic surgery is exactly the fact that the surgical effect is derived from initial gut hormonal changes triggered by the surgery. Many patients wonder if the size of their pouch determines the rate and amount of weight they can lose. Another common question is if they should expect a stomach stretch after bariatric surgery.

It is sometimes hard to understand the concept that when bariatric surgeons create a small pouch for the gastric bypass or a small long stomach for the sleeve gastrectomy the long-term effect of this surgery is NOT based on the size of the organ created but on the long-term endocrine and metabolic effects associated to diet and lifestyle changes.

By means now understood from people who research and treat obesity, it came to light that the long-term exclusion of parts of the gastrointestinal tract will trigger release, production and secretion of certain gut hormones (substance P, PYY, Ghrelin, GLP-1, adiponectin, etc..) that will signal back the intestinal cells, fat cells, brain cells and the body in general that your metabolism is “fighting back”, putting your metabolic rate in “shape” sort of speak.

The Imbalance and Function of the Fat Cell

Let’s dive a bit into this concept: obesity is a chronic disease that has multifactorial reasons, also we agree that a major factor is a disturbance in the fat cell metabolism. Based on this and our advancement in knowledge that the fat cells are an endocrine organ, you reach the agreement that obesity is a complete imbalance between the fat cell metabolism and the rest of the body, moreover, the gut plays a major role in absorption of sources of energy (nutrients like carbohydrates, fats, and protein).

This imbalance on the function of the fat cell (an endocrine organ or gland) directly affects how we regulate the amount of energy absorbed and spent by our body. The dysfunction of those fat cells places their metabolic set points in a matter of generating impulses (in the form of small hormones or peptides) that signal the rest of our body to be less efficient on burning energy (fat, carbohydrates), in addition to less energy expended for daily routines. This is essentially why we see obese patients stating that even on a diet they stop losing weight, or slowly regain some of their weight back.

Well, the reason we are talking about all this metabolic function is to put down the concept that your bariatric surgery is based on how big or small your pouch really is!

Before we get into details of the metabolic function of bariatric surgery let’s review some basic concepts of some of the most commonly performed surgeries.

Vertical Sleeve Gastrectomy (Gastric Sleeve)

Vertical Sleeve Gastrectomy (VSG) is one of the most common weight loss procedures done in the United States.  The procedure involves surgical removal of the majority of the stomach along the greater curvature creating a tube or “sleeve” like structure.  This is done with the assistance of a calibrating tube or “bougie” that is placed through the mouth and down the esophagus into the stomach.  The sleeve is then created using a linear stapling device around the bougie.  A bougie device comes in different available sizes and it is a surgeon preference on what size device they use.

Roux en Y Gastric Bypass (Gastric Pouch)

The gastric bypass or Roux en Y gastric bypass (RNY) is the creation of a pouch based on the lesser curvature of the stomach that afterward is connected straight to the jejunum, so the nutrients bypass the “old stomach (remnant stomach) and beginning of the small bowel”.

Both procedures have in common the fact that nutrients are not triggering neuronal and hormonal impulses at an area of the stomach (the fundus) responsible mainly for increasing appetite and generating signals to the rest of the body to accumulate energy. Some common questions are: Does the size of the bougie tube that the surgeon uses affect the amount of weight a person is going to lose?

Historically the sleeve gastrectomy was thought to be a “restrictive” procedure. This means that a patient loses weight because the procedure itself restricts the overall amount of food that a patient can eat which causes weight loss. Recent studies have shown that patients will have similar weight loss at 1 and 2 years regardless of what size pouch is made.

Although this procedure does “restrict” the amount of food someone can eat, it isn’t the most important reason that patients see dramatic weight loss. More important is the part of the stomach that is being removed.  The greater curvature and even more importantly the fundus or top portion of the stomach is removed during this procedure. It is in this area that gut hormones such as ghrelin are produced that alter appetite suppression and the amount of inflammation produced by the body which ultimately leads to weight loss.

Will the Stomach Stretch After Bariatric Surgery?

Regardless of what size sleeve or gastric pouch is created, there will be some stretching of the pouch over time.

Weight gain can and does occur in some patients that have had bariatric surgery. It is important prior to surgery to start making healthy lifestyle changes and start an exercise regimen. The goal after surgery is that with the alteration of gut hormones from the surgery itself and continuing healthy eating habits and a regular exercise routine, that patients will lose weight and keep the weight off.

Exercise has been shown to increase the release of a hormone known as irisin which can help potentiate the metabolic effects of bariatric surgery. Bariatric surgery is ultimately only a tool to help patients lose weight. It is the responsibility of the patient to make the lifestyle changes to help keep the weight off.

In summary, the fact that we are excluding in one way or another the fundus of the stomach, delaying gastric emptying and some other anorexigenic effects, this associated to the diet and lifestyle changes causes surgery to be so effective in treating obesity.


David Podkameni, MD, FACS, originally from Rio de Janeiro, Brazil, started his general surgery training at Mount Sinai Hospital in New York in 1996. He then returned to Brazil, where he became board certified in general and pediatric surgery. Dr. Podkameni finished his minimally invasive/laparoscopy training at the Cleveland Clinic in 2004. He serves as medical director of the Banner Gateway Bariatric Center in Gilbert, Arizona.