Gastric Sleeve Vs Gastric Bypass Surgery: Which is Safer & Effective?

Gastric Sleeve Vs Gastric Bypass

Gastric Sleeve Vs Gastric Bypass is a comparison of the two commonly performed bariatric surgical procedures. Both these procedures have outperformed most medical interventions for weight loss and diabetes control.

However, the efficacy and safety of each procedure need to be discussed with the patient before embarking on the procedure.

What is Morbid Obesity?

Morbid obesity and Super obesity are rather new terms as the pandemic of obesity spreads. As an obese person gets fatter and fatter, he/ she enters the circle of “Morbid Obesity“.

Not very uncommonly, we also come across very huge people who cross the cut-offs of “Morbid Obesity“. They are now termed “Super Obese“.

These terms may involve a little stigma as well, but from an obesity physician’s or a bariatric surgeon’s point of view, these terms reflect the severity of the disease and its associated complications.

Overweight is generally considered as people with a BMI exceeding 24 kg/m². For Asians, a BMI exceeding 23 kg/m² is considered obese.

Obesity is defined as a BMI of 30 to 35 kg/m². This is also called Class 1 Obesity. For Asians, this value corresponds to a BMI of 28 – 32 kg/m².

Moderate Obesity or Class II obesity is a BMI in the range of 35 to 40 kg/m².

Morbid Obesity or Class III Obesity is a BMI exceeding 40 k/m².

Other terminologies and definitions of obesity are being defined as more and more people gaining weight. These include:

  • Super Obese: When the BMI exceeds 50 kg/m²
  • Super Super or Supra Super Obese: BMI exceeding 60 kg/m²
  • Mega Obese: BMI exceeding 70 kg/m²

Obesity is not just the weight of the person. Because of its association with multiple diseases, it has recently been categorized as a disease state.

Diseases associated with obesity may range from mild illnesses like GERD to life-threatening such as cancers.

One good thing about Obesity as a disease is that it is totally preventable with a low-calorie diet, exercise, and medical interventions.

Although there has been a huge development in weight loss medications. The novel GLP-1, Semaglutide (Ozempic, Rybelsus, Wegovy), and the latest dual GLP-1 and GIP analogs such as Tirzepatide (Mounjaro) have been associated with significant weight loss.

However, these drugs still can not compete with bariatric surgical procedures (weight loss procedures).

Bariatric surgery is considered the best, if not the “Gold Standard” treatment of Morbid Obesity.

The field of Bariatric Surgical Procedures is also evolving and newer less invasive methods are being developed.

Some procedures are the least invasive such as the intragastric balloon, others are very invasive such as the Duodenal Switch.

However, until now the most commonly performed procedures are laparoscopic sleeve gastrectomy and Roux-en-y gastric bypass surgery. Both procedures have their pros and cons which are discussed here.



Procedures: Gastric Sleeve Vs Gastric Bypass

Gastric Sleeve is a rather simple procedure compared to Gastric Bypass which requires rearranging the gut and multiple anastomoses.

What is Gastric Sleeve or Sleeve Gastrectomy?

A gastric sleeve is a procedure that is performed under general anesthesia. The patient is completely unconscious during the procedure, unlike endoscopic procedures where the patient is awake.

The stomach is mobilized and a specifically sized bougie is placed in the stomach. A Bougie is shaped like a banana that helps the surgeon decide as to how much volume of the stomach needs to be preserved and how much to resect.

The volume of the stomach equivalent to the volume of the bougie is preserved while the rest of the stomach is resected with the help of a linear stapler.

Gastric Sleeve Surgery
Gastric Sleeve Surgery



The stomach that remains is roughly 20% of the original volume. This means before Gastric Sleeve, one can store about 2 to 4 liters of food while after Gastric Sleeve, one can only store 400 ml to 800 ml of food in the stomach.

This volume is sufficient enough to store the required amount of food and helps a person lose a significant amount of weight over six months.

At the end of the stomach is a functional valve called the “Pylorus” which is preserved in this procedure. This helps the person to keep the food flowing slowly into the small intestine. Thus the chances of “Dumping Syndrome” is minimized.

Dumping syndrome is a condition when food with high osmolality is suddenly absorbed from the intestine into the systemic circulation. This draws in fluid from the systemic circulation resulting in hypotension and dizziness. The patient may feel bloated and develop nausea, vomiting, or diarrhea.

What is Roux En Y Gastric Bypass or Simply Gastric Bypass?

Compared to Gastric Sleeve, Roux en Y Gastric Bypass or Gastric Bypass is a more complex procedure.

Gastric Bypass requires resection of the gut at multiple points and anastomosis or joining of different parts of the intestine. Hence, Gastric bypass requires complex dissection.

Because of the complex nature of the procedure, Gastric Bypass is associated with an increased risk of postoperative complications.

The most common complications that are not seen in patients who undergo Sleeve Gastrectomy are:

  • Leak at the site of the surgical anastomosis (Leak at the joints, where two parts of the intestines have been joined)
  • Intestinal dehiscence resulting in intestinal obstruction
  • Dumping syndrome
  • Late recovery following the surgery.

Gastric bypass surgery is performed in the following manner:

  • First, the stomach is cut to make a small pouch for food. The volume of the stomach that remains functional can accommodate about 150 to 300 ml of food.
  • The rest of the stomach is excised with a linear stapler.
  • Next, about 100 cm of the proximal jejunum is cut. One end of the jejunum is joined with the distal portion of the stomach, the other end is joined with the duodenum, and with a side-to-side anastomosis, the remaining part of the jejunum is connected, making a “Y“.
  • The term “Rou-en-Y” is derived from its complex anatomy.
Gastric Bypass Surgery
Gastric Bypass Surgery


The Roux-en-Y Gastric Bypass helps a person lose weight by:

  • Reducing the volume of the stomach
  • Reduces the small intestinal length to effectively mix with biliary and pancreatic juices.

Because the gut is shortened, patients who undergo Gastric Bypass may develop nutrient, mineral, and vitamin deficiencies.

It may also impair the absorption of life-saving medicines in patients with multiple co-morbid conditions. Therefore, it is the least preferred procedure in patients who are on multiple medications or have serious cardiovascular illnesses.



Weight Loss Comparison of Gastric Sleeve Vs Gastric Bypass:

Both Gastric Sleeve and Gastric Bypass are effective bariatric surgical procedures. These types of weight-loss surgical procedures can help you lose half of your weight in just six months.

The weight loss effects of both these procedures are not solely related to the restrictive effects of the newly made tiny stomach. This does not allow the stomach to accommodate food exceeding 300 ml in cases of RYGB and 800 ml in cases of Sleeve Gastrectomy.

These bariatric surgical procedures also have a significant impact on the gut-brain and neuroendocrine axis. This causes a marked reduction in the levels of the satiety hormone, Ghrelin.

Hence, patients do not feel like eating and are full all the time. There is also a significant reduction in cravings for foods with a high glycemic index.

RYGB and gastric sleeve have both been found to be effective in reducing significant body weight in multiple clinical trials and meta-analyses over both short-term (18 to 36 months) and long-term (more than 36 months) periods.

In one study patients who underwent a bariatric surgical procedure were followed for five years. These included 228 patients who had undergone Laparoscopic sleeve gastrectomy and 229 patients who had Roux-en-Y gastric bypass (RYGB) done.


Gastric Sleeve

RYGB (Gastric Bypass)

% Weight Loss55.5%62.7%

RYGB or gastric bypass was considered more effective in reducing body weight compared to Gastric Sleeve or LSG.

Another multicentered trial compared the weight loss effects of Gastric Sleeve Vs Gastric Bypass at 1, 2, and 3 years of follow-up. The results were comparable. Patients in the RYGB group had a greater weight loss but the results were not statistically significant.

The table here summarizes the results:

% Weight loss

Gastric Sleeve

Gastric Bypass

After 1 year72.3%76.6%
After 2 years74.7%77.7%
After 3 years70.9%73.8%

Another study comprising about 240 patients was conducted and patients were followed for 7 years. After 7 years, patients in the RYGB group (Gastric bypass) had significantly greater weight loss compared to those who underwent Gastric Sleeve.

% Weight Loss



After 7 year47%55.5%

Almost all the studies conducted on obese and morbidly obese patients who underwent gastric sleeve or gastric bypass had significant weight loss, usually exceeding more than 50%.

However, Gastric Bypass (RYGB) was associated with greater weight loss compared to gastric sleeve.

In a Korean study, the percentage of weight loss in patients who underwent Gastric Sleeve Vs Gastric Bypass was comparable, however, the resolution in comorbid conditions was greater in patients who underwent Gastric Bypass. Re-operation rates were higher in patients who had RYGB done.

The weight loss effects in the study at three-month intervals are tabulated below [Ref]:

Results of Gastric Sleeve Vs Gastric Bypass after 3 Months

 Gastric SleeveGastric Bypass
Weight loss in Kgs11.59.8
% Weight Loss10.69.1


Results of Gastric Sleeve Vs Gastric Bypass after 6 Months

 Gastric SleeveGastric Bypass
Weight loss in Kgs21.320.9
% Weight Loss19.119.1


Results of Gastric Sleeve Vs Gastric Bypass after 9 Months

 Gastric SleeveGastric Bypass
Weight loss in Kgs24.228.6
% Weight Loss22.225.2


Results of Gastric Sleeve Vs Gastric Bypass after 12 Months

 Gastric SleeveGastric Bypass
Weight loss in Kgs2629
% Weight Loss2426.1


Results of Gastric Sleeve Vs Gastric Bypass after 15 Months

 Gastric SleeveGastric Bypass
Weight loss in Kgs27.333.7
% Weight Loss25.428


Results of Gastric Sleeve Vs Gastric Bypass after 18 Months

 Gastric SleeveGastric Bypass
Weight loss in Kgs26.829.3
% Weight Loss22.326.6

Curing Diabetes Type 2 with Gastric Sleeve Vs Gastric Bypass:

Weight loss has a significant impact on Diabetes. The term “Diabesity” was coined when researchers found that Obesity is the number 1 cause of Diabetes and curing obesity can cure diabetes.

Since Bariatric Surgical Procedures are associated with significant weight loss, they also help in the control and remission of type 2 Diabetes Mellitus.

The effect of bariatric surgical procedures on diabetes control and remission is because of:

  1. The direct effects of bariatric surgical procedures on the gut-neuroendocrine axis result in hormonal changes such as a reduction in the levels of Ghrelin, increased insulin production, reduced insulin resistance, and enhanced insulin sensitivity.
  2. The weight loss caused by a Gastric sleeve or gastric bypass can have a significant effect on diabetes. It has been proven in studies that a 10% reduction in body weight from baseline is associated with about 0.8 % improvement in HbA1C.

Both Gastric Sleeve and Gastric Bypass procedures have been associated with marked improvement in diabetes and a reduction in the dose of oral antidiabetic drugs as well as insulin.

Multiple randomized clinical trials evaluated and compared the rates of remission of Diabetes Mellitus Type 2 in people who had undergone Gastric Sleeve or Gastric Bypass surgery for complicated obesity (Morbid obesity and diabetes).

Diabetes Remission was defined per the ADA criteria as a person who has glycated hemoglobin (HbA1C) of less than 42 mmol/L and fasting blood glucose of less than 100 mg/dl for at least one year or more in the absence of antidiabetic drugs.

One study found complete remission of Diabetes in 60% of patients who had undergone Gastric Sleeve vs 77% of patients who had undergone Gastric Bypass (RYGB).

These are incredible numbers. 60 to 77% remission in diabetes has not been seen with any medical intervention so far.

We call diabetes the mother of all diseases, hence we are not just curing diabetes but all the diseases associated with diabetes.



Effect of Gastric sleeve Vs Gastric Bypass on other weight-related co-morbid conditions:

As morbid obesity is linked with many other medical conditions such as osteoarthritis, sleep apnea, hypertension, dyslipidemia, and cardiovascular diseases, treating morbid obesity may reduce the incidence of these co-morbid conditions as well.

Both Gastric Sleeve and Gastric Bypass surgeries are associated with a significant improvement in lowering the incidence of obesity-associated comorbid conditions.

However, Gastric Bypass (RYGB) is considered more effective in reducing the incidence and improving the condition in a person who has already acquired it.

RYBG (Gastric Bypass) better controls most of the comorbid conditions than Sleeve Gastrectomy.

The table below compares the effect of Gastric Sleeve vs Gastric bypass on obesity-linked comorbid conditions:

Co-morbid conditions

Gastric Sleeve

Gastric Bypass

GERDWorsensBetter Control
DyslipidemiasEqual to gastric bypass in short-termBetter in the long-term (after 7 years)
Sleep apneaSameSame
HypertensionReduction is not as much as Gastric bypassBetter Control
Quality of lifeSameSame


Safety of Gastric Sleeve Vs Gastric Bypass:

Until now, we know that Gastric Bypass is somewhat more effective than Gastric Sleeve. But, whether it is equally safe as well or not?

We know that RYGB or Gastric Bypass is a complex procedure and requires multiple anastomoses of different parts of the gut.

It is understandable that the more complex the procedure is going to be, the more complications and the less safe it is going to be.

Hence, Gastric bypass is associated with more complications than Gastric sleeve. Gastric Sleeve is a much safer procedure both in terms of short and long-term complications.

Some complications may be directly linked to the procedure anatomy while others may be a result of the physiological changes the procedure brings about.

GERD (gastroesophageal reflux disease) is more common in patients who undergo Gastric Sleeve whereas marginal ulcer and Dumping Syndrome are more common in patients who have undergone Gastric Bypass surgery (RYGB).

The percentage of patients undergoing a repeat surgery or a second operation within 30 days following Gastric Bypass Vs Gastric Sleeve was much greater in the Gastric Bypass group Vs Gastric Sleeve surgery.

One RCT found that 9 patients had to undergo repeat surgery after Gastric Sleeve vs 16 patients in the RYGB (Gastric Bypass) who had to undergo a repeat surgery within 30 days following the initial operation.

Similarly, the death or mortality rates following RYGB or Gastric bypass are also higher compared to Gastric Sleeve surgery.

In one study that comprised 207 patients, none of the patients in the Gastric Sleeve died within one year of the surgery, while 4 patients in the RYGB (Gastric Bypass) died within one year of the surgery.

Table summarizing the complications associated with the Gastric Sleeve Vs Gastric Bypass:


Gastric Sleeve

Gastric Bypass

Kidney StonesNoYes
Nutrient DeficiencyNoYes
Marginal UlcerNoYes
Dumping SyndromeNoYes
DeathsUncommonDocumented in clinical trials

In Conclusion:

Both Gastric Sleeve and Gastric Bypass surgeries are very effective in reducing body weight and the incidence of obesity-associated medical conditions.

RYGB or Gastric Bypass is more effective in reducing body weight and controlling or curing diabetes compared to Gastric Sleeve.

However, a Gastric sleeve is a much safer procedure compared to RYGB (Gastric Bypass).

It is important to select the appropriate patient for the appropriate surgery and discuss the pros and cons of each procedure with the patient before deciding which procedure to perform.



What do you think?

Written by Dr. Ahmed

I am Dr. Ahmed (MBBS; FCPS Medicine), an Internist and a practicing physician. I am in the medical field for over fifteen years working in one of the busiest hospitals and writing medical posts for over 5 years.

I love my family, my profession, my blog, nature, hiking, and simple life. Read more about me, my family, and my qualifications

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