<> <>
Health Hub

Gastric bypass vs sleeve: What's the difference?

Each offers a distinct approach to achieving weight reduction, but... what's the difference?

Gastric Bypass vs Sleeve: What's the Difference? | Juniper

When it comes to weight loss surgeries, gastric bypass and gastric sleeve are two of the most prominent procedures. Each offers a separate and distinct approach to achieving significant weight reduction, but... what's the difference? What are the risks? Is one more effective than the other?

The decision to undergo bariatric surgery is a serious one, so understanding the differences between the two methods is crucial for anyone who's considering having weight loss surgery. While both gastric bypass and gastric sleeve aim to promote weight loss, they diverge in their surgical techniques, mechanisms of action, and potential outcomes.

In this article, we'll dive into the nuanced dissimilarities between gastric bypass and gastric sleeve surgery, shedding light on the key factors that anyone should consider when navigating the path to transformative weight management.

What is gastric bypass surgery?

During gastric bypass surgery, the surgeon will create a small pouch from the stomach and connect it directly to the small intestine in order to reduce the size of the stomach and alter the digestive process [1][2]. A very effective weight loss surgery, it's also known as Roux-en-Y gastric bypass, because of the Y-shaped connection it creates between the stomach pouch and the small intestine.

A gastric bypass procedure is often recommended for people who are struggling with obesity, particularly when other weight loss methods have been ineffective. It is also recommended as an option for those dealing with obesity-related health issues, like type 2 diabetes, hypertension, and sleep apnoea. It is proven to be an effective method for long-term weight loss and improvement of obesity-related conditions [7].

However, gastric bypass is a major surgery, so it's crucial to consult with healthcare professionals to understand the potential risks and benefits of this bariatric surgery.

What is gastric sleeve surgery?

Gastric sleeve surgery (also known as sleeve gastrectomy), is another bariatric surgery designed to help people achieve significant weight loss [3]. Unlike gastric bypass, the gastric sleeve procedure does not involve rerouting the digestive system.

Rather, it permanently removes a part of the stomach, creating a new stomach pouch that is smaller and shaped like a sleeve or banana. This reduction in stomach size not only limits the amount of food one can consume but also reduces the production of the hunger hormone ghrelin, which helps to decrease one's appetite.

Generally considered a less complex surgery than gastric bypass, gastric sleeve surgeries may be recommended as a first-stage procedure for patients dealing with significant obesity or other surgical risks.

Of course, a gastric sleeve procedure is still a major surgery that carries potential risks and complications, and its success depends on the patient's commitment to lifestyle changes, including a healthy diet and regular exercise.

What are the differences between gastric bypass and gastric sleeve?

When it comes to gastric sleeve vs gastric bypass surgeries, there's a lot to consider. While they're both effective bariatric surgeries, their approaches, risks, and long-term considerations differ. The choice will most likely depend on factors like individual health, weight loss goals, and medical history. 

Some other factors to consider when weighing up gastric bypass vs sleeve surgeries are:


The eligibility criteria for gastric sleeve and gastric bypass surgeries share some commonalities, but there will also be differences based on individual health factors, weight loss goals, and healthcare providers.

Both procedures usually require candidates to undergo a thorough medical evaluation that will look at a person's medical history, psychological well-being, and commitment to post-surgical lifestyle changes.

Ultimately, the decision between gastric sleeve vs gastric bypass depends on individual health considerations, but some general considerations are:

Gastric sleeve surgery

  • Body mass index (BMI): Typically, individuals with a BMI of 40 or higher are eligible [4]. Those with a BMI of 35-39.9 may also be considered if they have obesity-related health issues.
  • Health conditions: Gastric sleeve surgery may be recommended for individuals with obesity-related health conditions, such as diabetes, high blood pressure, or sleep apnoea.
  • Commitment to lifestyle changes: Candidates should demonstrate a commitment to making long-term lifestyle changes, including dietary modifications and regular physical activity.

Gastric bypass surgery

  • BMI and health conditions: People with a high BMI, usually 40 or above, will often be considered eligible for gastric bypass surgery. Some people with a BMI of 35-39.9 who are also dealing with obesity-related health conditions may be eligible as well [4].
  • Type 2 diabetes: Specifically, bypass surgery may be considered more suitable for individuals with type 2 diabetes due to its potential impact on diabetes remission.
  • Gastroesophageal reflux disease (GERD): Gastric bypass may be preferred for individuals with GERD, as it can help alleviate symptoms [5].
  • Previous weight loss attempts: Some providers may consider the number of previous weight loss attempts when determining eligibility for gastric bypass.


The cost of gastric bypass and gastric sleeve surgery can vary widely based on several factors, including your location, the surgeon's fees, anaesthesia costs, pre-operative testing, post-operative care, and whether the procedure is covered by health insurance.

In the UK, the cost of gastric bypass surgery can range between £8,000 and £15,000 [6], while a sleeve gastrectomy can cost between £8,000 and £10,000.

However, private health insurance can cover part of these costs, so it's essential to thoroughly research and understand the breakdown of costs provided by the healthcare provider and consult with the insurance provider to determine coverage and out-of-pocket expenses.


The preparation for gastric sleeve and gastric bypass surgeries share many common elements.

Before any bariatric surgery, your doctor will perform a thorough medical evaluation that includes a review of your medical history, a physical examination, and any necessary blood tests or imaging. Some healthcare providers may also require a psychological evaluation, to ensure that the person is mentally ready to undergo the surgery and cope with the emotional aspects of significant weight loss, and is ready to make the necessary, ongoing nutritional and lifestyle changes after the surgery.

Bariatric surgery will usually come with some level of nutritional counselling, also. Some people will be required to go on a pre-operative diet in the lead-up to the surgery, which can reduce the size of the liver and minimise the risk of complications during the surgery. Patients will also learn about the dietary and lifestyle changes that they will need to make after the surgery, which is crucial for long-term success, as well as overall health and well-being.

Regardless of which bariatric surgery someone is having, it's crucial they follow their doctor's instructions to the best of their ability and attend all the required pre-operative appointments. Doing so will minimise the risk of any possible complications, and set the patient up for the greatest chance at long-term success.

Potential side effects

If you're considering any kind of weight loss surgery option, it's important to understand the potential side effects that may occur.

While the majority of people who undergo bariatric surgeries will see positive outcomes, like the loss of excess body weight and improved overall health, both surgeries have potential risks and side effects. It's also important to note that the severity and occurrence of these side effects can vary from person to person.

With that being said, here are some of the potential side effects of gastric sleeve vs gastric bypass procedures.

Gastric bypass surgery

  • Dumping syndrome: When food moves too quickly from the stomach into the small intestine, it can cause dumping syndrome [9]. Dumping syndrome can occur after eating foods high in sugar or fat, with symptoms of nausea, vomiting, weakness, sweating, and dizziness.
  • Nutritional deficiencies: Because the procedure reroutes the digestive tract, there is a higher risk of nutritional deficiencies, including deficiencies in iron, calcium, vitamin B12, and folate [8]. Lifelong supplementation and regular monitoring of nutrient levels are essential.
  • Marginal ulcers: Some individuals may develop ulcers near the surgical connection between the stomach pouch and the small intestine, leading to symptoms such as abdominal pain and bleeding.
  • Gallstones: Rapid weight loss increases the risk of gallstones, and some individuals may need to have their gallbladder removed during or after the surgery.

Gastric sleeve surgery

  • Reflux or heartburn: In some cases, gastric sleeve surgery may lead to increased reflux symptoms or heartburn. This can typically be managed with dietary modifications or medications.
  • Stenosis: Narrowing of the sleeve can occur, causing difficulty swallowing. This is a less common side effect but may require intervention.
  • Leakage: While rare, there is a risk of leakage along the staple line where the stomach is divided. This can lead to serious complications and may require additional surgery.
  • Nutritional deficiencies: Similar to gastric bypass, gastric sleeve surgery may also lead to nutritional deficiencies over time, particularly in iron and vitamin B12. Lifelong supplementation and regular monitoring are recommended.


The recovery process for gastric bypass and gastric sleeve surgeries shares some similarities, but there are differences due to the nature of each procedure. Bypass patients typically have a longer hospital stay (2-3 days) compared to gastric sleeve patients (1-2 days).

Both gastric sleeve and bypass patients will start with a diet of clear liquids and transition to pureed and soft foods before reintroducing solid foods, which helps the digestive system to adjust as the stomach heals.

Both procedures involve significant lifestyle changes, including dietary modifications and regular physical activity [4]. Patients are usually advised to avoid heavy lifting and strenuous exercise during the initial weeks post-surgery and gradually reintroduce physical activity under medical guidance.

Success rate

Comparing gastric sleeve vs gastric bypass surgery success rates is tricky because it can vary based on several individual factors.

Generally speaking, success in bariatric surgery is often measured by weight loss, improvement in obesity-related health conditions, and overall patient satisfaction.

Both gastric bypass surgery and sleeve surgery can result in significant, sustainable and long-term weight loss, although bypass surgery does tend to have slightly higher weight loss rates [8]. Likewise, both surgeries are associated with significant improvements to overall health in relation to obesity-related conditions, like type 2 diabetes, hypertension, and sleep apnoea [7].

With that being said, it's important to consider that these success rates can be influenced by factors such as adherence to post-operative guidelines, lifestyle changes, and ongoing medical management.

What are the pros and cons of each surgery?

Both gastric bypass and gastric sleeve surgeries are effective weight loss procedures, each with its own set of pros and cons.

Ultimately, the choice between gastric bypass and gastric sleeve should be based on individual health factors, preferences, and discussions with a healthcare professional.

As you know now, both procedures can be effective in promoting weight loss and improving obesity-related health conditions, but they have different considerations and potential risks [7]. It's important for individuals to thoroughly understand the pros and cons of each option before making a decision.

Here's a summary of the pros and cons of gastric bypass surgery:


  • Significant weight loss
  • Improvement in health conditions


  • Nutritional deficiencies
  • Dumping syndrome
  • Complex procedure
  • Potential for long-term issues

As for gastric sleeve surgery:


  • Effective weight loss
  • Simplicity of procedure
  • No rerouting of the digestive tract
  • No dumping syndrome
  • Improvement in health conditions


  • Potential for reflux
  • Non-reversible
  • Risk of stenosis
  • Weight loss slightly less than gastric bypass

Non-surgical weight loss options

Whether it's gastric sleeve or gastric bypass surgery, any bariatric surgery is a major decision to make, and generally only recommended if other weight loss methods have been unsuccessful.

If you want to lose weight without undergoing weight loss surgery, Juniper's Weight Reset Programme might be the option for you.

Designed by
UK clinicians and dietitians, this programme is a medical pathway for long-term weight loss, without any surgical procedure. With breakthrough weight loss medication that helps suppress appetite and improve metabolic function, as well as ongoing support and lifestyle coaching from our dietitians and health coaches, Juniper can help you achieve your weight loss goals.

Image credit: Getty Images