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Sleeve Gastrectomy vs Gastric Bypass

The Surgeons Collective Weight Loss

Sleeve or Bypass - What’s the difference? Which is best?

Both sleeve gastrectomy and gastric bypass are surgeries designed to restrict the intake of food long term, with the aim of reducing weight. However, the two operations are performed very differently. 

The goal is the same as traditional gastric bypass surgery: to reduce the size of the stomach as well as bypassing a stretch of the intestines. This decreases the amount of food that can be consumed and causes some malabsorption of calories, resulting in weight loss.

Gastric Sleeve Surgery

A gastric sleeve surgery is a common and new type of weight loss surgery, performed via keyhole surgery.

The name comes from the process itself. It refers to the way your stomach is transformed into a narrow “sleeve” like shape, by removing approximately 80% of the stomach.

The stomach normally holds a volume of between 2-4 litres. Using a stapling device, the bariatric surgeon will reduce that volume to roughly 15-20% of its original size. Typically the stomach size after a gastric sleeve procedure is around 200ml.

Gastric Bypass Surgery

During a gastric bypass, the top of the stomach is first separated from the rest of the stomach, creating a small and narrow “pouch”. The second step is the “bypass” component, where the new stomach pouch is joined to the small intestines. There are various ways this can be done, such as: 

  • Roux-en-Y Gastric Bypass (RYGB)
  • Single Anastomosis Gastric Bypass (also known as the “Mini-Bypass”)

What are the benefits and risks for each procedure?

Each surgery has specific benefits and risks that you may like to consider. It is important to know that each situation is unique, and what is right for you will depend on your specific health and long-term goals.

Here, we list some of the pros and cons to consider for these two bariatric surgeries. 

The pros of gastric sleeve surgery:

  • Highly effective in terms of weight loss results and almost comparable to Roux-en-y gastric bypass (RYGB).
  • There is no foreign body implanted (like the band in a Gastric Band procedure).

  • No anastomoses (the joining of small intestines) needed like a RYGB.
  • No risk of internal hernia as seen with RYGB.

  • Less complex procedure, therefore, shorter procedure time and less anaesthetic used.
  • Limits the ingestion of food and hunger by reducing the hunger hormone “ghrelin”. 
  • Maintains natural digestion afterwards.
  • Lower risk of mal-absorption and malnutrition compared to RYGB.
  • Lower risk of nutritional deficiencies.

The cons of a gastric sleeve surgery:

  • Not reversible.
  • Risk of “staple line leaks”.
  • Narrowing of the sleeve stomach causing difficulties when eating.
  • Heartburn (which may sometimes require additional surgery).

The pros of roux-en-y gastric bypass:

This is often the surgery of choice for patients with significant heartburn (GORD -  Gastro-oesophageal reflux disease), or with complications related to heartburn such as oesophagitis, ulcers or Barrett’s oesophagus.


Can be offered as a “revision” or additional operation to treat problems arising from other types of weight loss operations, such as Gastric bands or Gastric Sleeve.

Gastric bypass risks include:

  • More complex procedure with a longer duration.
  • Lifelong dependence on nutritional and vitamin supplements.
  • Medical and dietician follow-ups are lifelong and compulsory.
  • Ongoing need for regular blood tests.
  • Risks of nutritional deficiency, especially Vitamin B12 and folate, with the risk of anaemia.
  • Risk of serious malabsorption and malnutrition.
  • Risk of dumping syndrome.
  • Risk of internal hernia and small bowel obstruction.
  • Risk of leaking along the staple line or anastomoses.
  • Risk of ulcers between the stomach and intestinal anastomoses (marginal ulcers).

So which one is right for me?

As you can see, there are many pros and cons to consider for each surgery. The right choice for you will depend on a number of specific factors, including your current state of health and your goals for after the surgery. If you’d like to discuss this in more detail, come in to speak with our team. We’re ready to give you all the help you need to make your decision.

Make an appointment

Gemma Gilbert Dietitian at The Surgeons Collective Perth

About the author

Mr Siva Sundararajan | Bariatric & General Surgeon

Mr Siva Sundararajan is a qualified general and obesity surgeon. His main areas of interest are weight loss surgery, gall bladder and hernia surgery. To ensure that the best possible care is provided to his patients, he has undertaken extensive training in the UK, Australia and Europe.

More information about Mr Siva Sundararajan