Gastric Bypass

Laparoscopic Gastric Bypass Surgery


What is gastric bypass surgery?

Gastric bypass surgery, (Roux-en-Y gastric bypass), is a form of weight loss surgery that operates by reducing the size of your stomach and rerouting a portion of your digestive system. As a result, your meal portions are restricted, and your body absorbs less food. The procedure is carried out using laparoscopic (keyhole) surgery while you are under general anesthesia, typically lasting from one to three hours.

On average, individuals undergoing this procedure generally achieve weight loss ranging from 60% to 70% of their excess body weight.

About the operation:

Initially, a small pouch is made near the upper section of your stomach using staples. A segment of your intestine is connected to this gastric pouch, bypassing the remainder of your stomach and the upper portion of the intestine, where the majority of nutrients and calories are typically absorbed.

The small upper part of your stomach promptly fills with food, inducing a sensation of fullness, and then directly traverses to the middle portion of your small intestine before progressing through the remainder of your digestive tract. Due to the shortened length of the digestive system, calorie absorption should be reduced.

This procedure can be executed in two ways: through standard open surgery or via laparoscopic surgery. The laparoscopic approach involves the creation of several (5-6) minuscule incisions and offers numerous advantages over open surgery, such as faster recuperation, shorter hospital stays, and a significantly reduced risk of wound infection. Patients also commonly report less discomfort and a quicker return to regular activities.

What are the alternatives?

Additional surgical alternatives include laparoscopic gastric banding or laparoscopic sleeve gastrectomy.

Typically, surgery is advised solely when non-surgical interventions like dietary adjustments, physical activity, and medications have not yielded the desired outcomes.

What are the advantages of having a gastric bypass?

Substantially more and swifter weight loss compared to gastric band or sleeve gastrectomy procedures.

In up to 80% of cases, an immediate remission of type 2 diabetes and improvements in blood pressure occur within days of undergoing the operation.

What are the risks?

Gastric bypass surgery is typically considered a safe procedure.

Nevertheless, to ensure you can make an informed decision and provide consent for the surgery, it's important that you are aware of potential side effects and the associated risks and complications of this procedure.


These are the unwanted yet mostly temporary outcomes of a successful treatment.

You are likely to experience bruising, pain, and skin swelling around the healing incisions.

After meals, you might encounter nausea or vomiting, particularly if you comsume too much. Eating excessive amounts of sugary foods can lead to an uncomfortable sensation known as "dumping," which may trigger feelings of sickness, faintness, or diarrhea. During such episodes, it's recommended to hydrate and reduce sugary intake until the sensations subside.

Over the long term, your controlled diet might lead to deficiencies in nutrients like iron, calcium, and vitamins. This could necessitate the ongoing use of multivitamin/mineral supplements.


These are instances where problems arise during or after the surgery.

Most individuals undergoing this surgery will not encounter significant complications.

As with any surgical procedure, undergoing general anesthesia carries inherent risks. Potential complications include unforeseen reactions to the anesthesia, excessive bleeding, or the development of blood clots, typically within leg veins (deep vein thrombosis, DVT) or the lungs (pulmonary emboli, PE). These risks escalate for individuals with pre-existing medical conditions like heart disease or high blood pressure.

Listed below are some of the potential complications that may arise after a gastric bypass operation:

  • Infection: Typically, antibiotics are administered during surgery to prevent infection.
  • Organ Damage in Abdomen: Damage to other abdominal organs might necessitate subsequent surgical repair.
  • Anastomotic Leak (Join): The point where your intestine is reconnected to your stomach pouch could leak within the initial days, potentially requiring further corrective surgery.
  • Anastomotic Stricture or Ulceration (Join): The reconnection point between your intestine and stomach pouch might narrow or develop ulcers post-surgery, requiring endoscopy with or without dilatation or additional surgery for resolution.
  • Internal Herniation and Adhesion Issues: Additional surgery might be needed to address internal herniation and adhesion problems.
  • Gallstones: Swift weight loss carries a risk of gallstone formation, which might necessitate surgical removal due to associated pain.
  • Inadequate Weight Loss: It's plausible that you may not achieve the desired weight loss, or previously lost weight might be regained after bypass surgery.
  • Conversion to Open Surgery: In certain instances, your surgeon might need to shift from keyhole surgery to open surgery if safety concerns arise. This involves a larger abdominal incision.

The specific risks are tailored to your circumstances and will vary from person to person. Overall, there is a 2-5% risk of encountering adverse effects (as outlined above) and a 1 in 200 (0.5%) chance of death attributed to this procedure. 

How long does it take to get better from surgery?

After the operation, a typical hospital stay lasts around two to three days. Full recuperation from a gastric bypass generally takes two to three weeks.

Is the gastric bypass operation reversible? 

The gastric bypass operation is primarily regarded as a lasting approach to weight loss.

Yet, in exceptional cases, full or partial reversals are feasible, such as in emergencies or when severe side effects or complications emerge from the procedure.

A complete reversal necessitates another operation of comparable or greater scale, carrying comparable or greater risks than the initial surgery. Consequently, reversal operations are typically contemplated only if lasting side effects or complications are encountered. A complete reversal often results in the regain of previously lost weight.

An alternative to full reversal, occasionally performed, is a procedure to reduce the portion of the bypassed bowel. This doesn't enable larger food intake but enhances food absorption.

This factsheet caters to individuals considering or seeking information about gastric bypass surgery. While every effort has been made to provide details about gastric bypass surgery, certain details might not have been addressed here. Additionally, your care will be tailored to your specific needs, potentially varying from the description provided here.

Further information:

Association for the Study of Obesity (ASO) 020 8503 2042

British Obesity Surgery Patients Association (BOSPA) 0845 602 0446