Gastric Bypass Vs. Gastric Sleeve Surgery

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When contemplating the choice between gastric bypass vs gastric sleeve surgery, it’s crucial to consider various factors. Unlike the laparoscopic adjustable gastric band (Lap Band), both of these procedures are permanent, effectively curb hunger, and result in the most substantial weight loss percentages. To accurately compare gastric sleeve surgery with gastric bypass surgery, let’s analyze the following data:

Amount of Weight Loss

Understanding the anticipated weight loss post-surgery is crucial. Equally significant is recognizing that sustained weight loss depends heavily on your lifestyle and daily habits following the procedure. Engaging in healthy exercise routines and adopting nutritious eating habits—such as ensuring a minimum intake of 60 grams of protein per day, opting for planned meals over grazing or unplanned snacking, etc.—typically yields more substantial weight loss than the average figures provided below.

Without incorporating these healthy lifestyle changes after undergoing gastric bypass or gastric sleeve surgery, there’s an increased likelihood of regaining a significant amount of weight.

In the initial year after gastric bypass, patients typically shed 60 to 80 percent of excess body weight. Meanwhile, gastric sleeve patients experience a weight loss ranging from 50 to 70 percent of excess body weight over a two-year period.

Average of Gastric Bypass vs Gastric Sleeve

People with a BMI exceeding 45 often receive recommendations for gastric bypass. Gastric bypass is the preferred choice due to its slightly higher average weight loss and its induction of ‘dumping syndrome.’

As gastric bypass induces ‘dumping syndrome,’ patients experience adverse effects such as nausea, sweating, and an overall sense of discomfort shortly after consuming sweets, a substantial amount of carbohydrates, or high-fat foods, including fried foods. This unfavorable reaction serves as a deterrent, aiding in the reduction of binge eating and the restriction of high-sugar and high-fat food selections.

Nevertheless, numerous surgeons are discovering that gastric sleeve surgery proves highly beneficial for individuals with a BMI exceeding 45 as well.

During gastric sleeve surgery, 70% of the stomach, where the hunger hormone ghrelin is generated, is removed.

This rapidly and efficiently diminishes hunger, resulting in significant weight loss.

Interestingly, gastric sleeve surgery was initially developed as the initial phase in a multi-stage process designed for individuals with a BMI exceeding 50. Surgeons would construct a sleeve and subsequently complete the remaining steps of the procedure (such as rerouting intestines) after the patient had shed some weight. However, a majority of patients achieved sufficient weight loss from the initial part of the procedure (the sleeve), obviating the need for a second intervention.

Utilize this calculator to determine your estimated weight post-gastric sleeve surgery and gastric bypass surgery.

Comparison of Surgical Times

Gastric Bypass vs Gastric Sleeve Operation Time

Undergoing anesthesia inherently carries risks, with a higher risk profile for individuals classified as obese. This risk escalates further when coupled with co-morbidities such as high cholesterol and high blood pressure. While procedure time is a relatively minor consideration in the overall decision-making process, it should be factored in.

By assimilating this data alongside other relevant factors, individuals can make more informed decisions regarding which procedure aligns better with their needs.

A review published in Obesity Surgery, titled “A Review of Laparoscopic Sleeve Gastrectomy for Morbid Obesity,” scrutinized numerous studies, calculating the average procedural times for the two bariatric procedures. The gastric bypass procedure had an average duration of 2 hours and 44.8 minutes (164.8 minutes), while the gastric sleeve procedure averaged 1 hour and 40.4 minutes (100.4 minutes).

Weight Loss Speeds

As mentioned in the introduction of this article, gastric bypass surgery initially results in greater weight loss; however, over three years or more from the procedure date, the weight losses from gastric sleeve surgery begin to approach those achieved with gastric bypass surgery.

Additionally, the Body Mass Index (BMI) must be considered in the equation, as it significantly influences the speed and extent of weight loss. A patient’s Initial Body Mass Index (IBMI) plays a crucial role, with a higher IBMI correlating with a more substantial drop in the patient’s BMI, especially after three years or more, irrespective of the chosen procedure. Essentially, individuals with a higher body weight before surgery are likely to experience faster weight loss immediately after the procedure.

The majority of weight loss with gastric bypass occurs within the initial year. In contrast, patients undergoing gastric sleeve surgery continue to experience weight loss through the second year before reaching their target weight.

The Benefit of Gastric Bypass Over Gastric Sleeve

What makes gastric bypass the ‘Gold Standard’ while gastric sleeve surgery is not accorded the same status?

Gastric bypass surgery holds the status of being the longer-established option. Its outcomes and complications have undergone extensive study, confirming its benefits. Every bariatric surgeon with fellowship training has dedicated a significant portion of their training to performing this procedure.

The malabsorptive aspect of gastric bypass, achieved by bypassing a segment of the intestines (resulting in a shorter intestinal tract), effectively reduces calorie absorption time, contributing to weight loss. Although gastric bypass is more complex and carries a slightly higher overall risk, it is associated with greater weight loss and often induces dumping syndrome.

For individuals with a history of acid reflux (GERD), surgeons may recommend gastric bypass over gastric sleeve surgery due to the lower risk of GERD post-gastric bypass.

Gastric Sleeve vs Gastric Bypass Side Effects

Bariatric surgery is considered a relatively safe procedure.

As per the American Society for Metabolic and Bariatric Surgery (ASMBS), the risk of a major complication is approximately 4%, significantly lower than the risk associated with developing severe health issues related to obesity.

Some factors that can complicate any surgery, including bariatric surgery, encompass:

  • Hemorrhage, involving excessive blood loss.
  • Deep vein thrombosis, characterized by the formation of blood clots in the leg.
  • Pulmonary embolism, marked by the development of blood clots in the lung.
  • Side effects stemming from general anesthesia.
  • Infection at the incision site.
  • Postoperative pain.
  • Pneumonia.

Gastric Sleeve vs Gastric Bypass Pros and Cons

According to the ASMBS, approximately 90% of individuals undergoing bariatric surgery achieve a 50% reduction in their excess body weight and are able to sustain a significant portion of this weight loss in the long term.

Success rates, however, vary based on the specific type of surgery performed.

In a 2014 study focusing on individuals with morbid obesity who underwent bariatric surgery between 2008 and 2010, participants who had laparoscopic gastric sleeve surgery exhibited an average loss of 49.2% of their excess body weight after 6 months. During the same period, those who underwent laparoscopic gastric bypass surgery experienced an average loss of 52.9% of their excess body weight.

A subsequent 2018 follow-up study investigated the weight loss outcomes of the same participants 5 years post-surgery. Over this period, individuals who had laparoscopic gastric sleeve surgery maintained an average weight loss of 49% of their excess body weight, while those who had laparoscopic gastric bypass surgery achieved an average loss of 57% of their excess body weight.

One of the notable advantages of both gastric sleeve and gastric bypass surgery is their substantial reduction in the risk of obesity-related conditions.

  • type 2 diabetes
  • high blood pressure
  • stroke
  • fatty liver disease
  • sleep apnea
  • hyperlipidemia
  • heart disease
  • knee or hip pain


Bariatric surgery procedures. (2021).

Carter J, et al. (2014). Predictors of hospital stay following laparoscopic gastric bypass: Analysis of 9,593 patients from the National Surgical Quality Improvement Program.

Metabolic and bariatric surgery. (2021).

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