Roux-en-Y Gastric Bypass


Roux-en-Y  Gastric Bypass

The Roux-en-Y gastric bypass is a commonly performed weight loss surgery that, when combined with diet and lifestyle changes, enables significant weight loss. It is particularly popular in those with diabetes due to hormonal changes caused by the surgery often leading to a reduction in the need for diabetic medication.

Who Qualifies for A Gastric Bypass?

You may be considered for a gastric bypass if you have a body mass index (BMI) that is greater than 40 (or greater than 35 if you experience a weight-related illness, such as type 2 diabetes, hypertension, sleep apnoea etc.) and you have tried other methods of weight loss, such as dieting, without long-term success.

The Surgery

The gastric bypass procedure takes between 2-3 hours and is performed with laparoscopic (keyhole) technique under general anaesthesia. This involves making several small cuts (between 5 and 15mm in length) into the abdomen where the surgical instruments, including a camera, are inserted. The top of the stomach is then stapled to form a small pouch (that is able to hold 30-50ml), which becomes the new, smaller, stomach and is completely separate to the rest of the stomach. The new stomach pouch is then joined to the middle part of the small intestine (the jejunum) so that the first part of the small intestine (the duodenum) is bypassed. The rest of the stomach and the duodenum remain in the body but are no longer used for food digestion.

How does the surgery help you to lose weight?

The gastric bypass procedure assists patients to lose weight in two ways:

  • Reducing the size of the stomach. This limits the amount of food that can be eaten at any one time to less than a 1/4 of what you can eat now.
  • Decreasing the amount of calories you absorb from your food as a result of bypassing the duodenum (the first part of the small intestine).

It is important to remember that surgery is a tool to assist your weight loss journey and not the whole solution. It is vital that healthy lifestyle behaviours are practiced to get the best result from the procedure. Eating a variety of vegetables, fruits and lean proteins as well as limiting your intake of high-calorie foods such as sweets, take-aways and sugary-drinks will maximise your weight loss after surgery. If eating behaviours are not adapted after surgery, weight loss will be slowed and limited and weight regain can occur. More detailed information about healthy eating behaviours will be provided during your visit with the dietitian.

Expected weight loss

The gastric bypass is successful in initial weight reduction as well as long-term weight maintenance. Most people can expect to lose 25 to 35% of their total body weight in the first 12 - 18 months after surgery.

Advantages of the Gastric Bypass

  • It is particularly effective for patients with a larger BMI as the procedure has more predictable weight loss outcomes compared to other less-invasive procedures, such as gastric banding.
  • There is a strong, positive effect on diabetes. Hormonal changes resulting from surgery mean that most patients have an almost immediate reduction in their need for diabetic medication and some are able to completely stop diabetic medication altogether.
  • It tends to produce the greatest improvement in blood pressure, cholesterol levels, and other obesity-related health issues.
  • It does not require any on-going adjustments that are required with other procedures, such as the gastric band. However, regular follow-up is necessary to ensure your rate of weight loss is appropriate and food intake is nutritionally adequate.
  • It is effective for people who tend to prefer high sugar or high fat foods. Gastric bypass can result in dumping syndrome following the ingestion of high sugar and high fat foods. Symptoms of dumping syndrome, such as stomach cramps and diarrhoea, are unpleasant and therefore patients tend to reduce their intake of high calorie, sweet foods in order to avoid them. 

Disadvantages of a Gastric Bypass

Disadvantages of the Roux-en-Y gastric bypass are generally related to the magnitude of the surgery:

  • Although it is technically possible to reverse this operation, this is much more involved than with gastric banding (for example) and reversal is only undertaken in very rare situations.
  • Complications, although rare, are generally more serious than with other weight loss procedures, such as the gastric band.
  • There is a higher risk of nutritional deficiency due to the reduced absorption of vitamins and nutrients. Life-long vitamin and mineral supplementation is essential to prevent deficiency following surgery. Long-term follow-up with your surgeon and dietitian to monitor your nutritional status is very important.

Risks of the Gastric Bypass

As with any surgical procedure, there are risks associated with the gastric bypass procedure. It is important to understand these risks before proceeding with the operation. The following is a comprehensive list of the risks that can occur. It is extensive and is not intended to worry you, but simply inform you about the range of possible complications, regardless of how rare some of them may be.

Possible Acute Complications

Complications that can occur during the surgery or shortly after include:

  • Bleeding - which can require blood transfusion and occasionally repeat operation. Bleeding occurs in roughly 1% patients.
  • Infection – which may require treatment with antibiotics and occasionally repeat operation.
  • Leak - a leak of fluid can occur through the new join between the stomach and intestines. This can occur in the first few days after surgery and may require repeat operation. If a leak persists it can create a passage between the stomach wall and the skin or wound (fistula) or cause persistent infections within the abdomen (abscesses). This complication is potentially life-threatening and can extend the length of stay in hospital to weeks or potentially months after surgery. Leakage occurs in less than 1% of cases.
  • Ulcers - may form in the new stomach pouch after a gastric bypass. For this reason, patients need to take anti-ulcer medication for 3 months after surgery. Sometimes ulcers develop despite this and require additional therapy to manage.
  • Damage to organs – unintentional injury to the organs near the area of operation. This may require a repeat operation to repair the damaged organs.
  • Blood clots – such as deep vein thromboses (clots in the veins, usually of the legs) and pulmonary embolus (clots in the lungs).
  • Pneumonia/ chest infection

We take measures directly aimed at reducing these risks, but if complications occur, additional treatment may be necessary.

Possible Long-Term Complications

  • Wound hernia – hernia formation at the site of wound closure. This may require repeat surgery, sometimes in the emergency setting.
  • Internal hernia – occasionally, loops of intestine can become entangled and get stuck. This requires a repeat operation. If there are any unexpected abdominal complaints it is important to be assessed quickly by the surgeon.
  • Anastomotic stricture – It is important to keep the new connection between the stomach and the intestines small so as to achieve the right amount of weight loss. Sometimes this means the connection is too tight. This complication occurs in less than 10% of patients and may require stretching under endoscopy (camera inserted through the mouth into the stomach).
  • Adhesions – any surgical procedure in the abdomen can cause adhesions (scar tissue). This can occur any time after the operation and can sometimes cause problems with the bowel getting stuck or twisted. Hospitalisation and repeat operation may be necessary.
  • Other - As this surgery affects the function of the gut, some patients are unable to tolerate adequate intakes of food, which can result in the need for long-term nutritional support via intravenous methods, called TPN (total parenteral nutrition).
  • Failure of weight loss/weight regain – this usually occurs when dietary advice is not followed. Regular over-eating can stretch the new small stomach pouch making it easier to eat larger volumes at meal times in the future.

Dumping syndrome

Dumping syndrome is a group of signs and symptoms that usually occurs due to poor food choices. It is caused by high sugar or high fat foods passing through the stomach and into the small intestine too quickly. Symptoms can include cramping, diarrhoea, nausea, dizziness, weakness and fatigue. More information regarding dietary advice to avoid dumping will be provided during your visit with the dietitian.

Pre-Operative Diet

After receiving your date for surgery, you will be advised to start a very low-calorie liquid meal replacement diet for the 14 days prior to your surgery. OptifastTM is the recommended meal replacement and is readily available from your local Chemist. The diet is intended to kick-start your weight loss prior to surgery, with the aim of reducing the size of your liver to optimise the safety of the procedure. More detailed information will be provided to you during your appointment with the dietitian.

Post-Operative Care

Generally, patients will stay in hospital for 2-3 days following the procedure. After the procedure you will slowly sip clear fluids only (water, black tea, broth, juices). Once the size and function of the pouch is confirmed, you will be able to drink fluids freely for the remainder of your hospital stay. During the next 4-6 weeks, while your body heals, you will gradually increase the consistency and volume of food you eat. Further information, including a healthy dietary guidelines booklet, will be provided at your appointment with the dietitian.



Your first post-operative clinic visit will be arranged for 2-4 weeks after your surgery. At this appointment your surgical wounds will be assessed, and any other issues will be discussed.


The dietitian will phone you within the first week following your surgery to review your food intake. Your first post-operative clinic visit with the dietitian will be at 3 to 6 weeks following surgery and then monthly for the first 6 months, and every 3 to 6 months for the first two years.

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