Gastric Sleeve vs. Gastric Bypass: Differences, Pros, Cons

Dr. Christopher McGowan
August 20, 2020

If you’re like most Americans, you’ve tried multiple times to lose weight over the years, but you haven’t been able to get the body you really want. Even with focused discipline, a restricted diet, and exercising religiously, the results often never come. Some people in this situation have opted for bariatric surgery, but that can be an intimidating prospect. At True You Weight Loss, we focus on non-surgical approaches that produce results that are similar to surgery, without the surgery. If you are reviewing current weight loss options, including non-surgical ones, it’s still important to understand the two most popular bariatric surgeries performed today: gastric bypass and gastric sleeve.

What’s the Difference Between These Two Surgeries?

In a way, both types of weight loss surgery are similar in that they rely on the same basic idea: reduce the size of the stomach in order to automatically reduce the number of calories that can be consumed in a single sitting. Such a reduction in stomach volume—and the resultant caloric deficit—is designed to promote weight loss over the long term by essentially retraining the body to expect fewer calories. The decreased stomach capacity means feeling full sooner, and the net effect of feeling full is that it becomes very difficult to overeat. 

Though they both work by decreasing stomach capacity, one of the main differences between the two surgeries is the primary means of achieving a caloric deficit. In gastric sleeve surgery, the smaller stomach size simply means you’ll generally be less hungry; this essentially forces you to eat less because the new stomach simply can’t hold the same amount of food. With gastric bypass, the nature of the procedure makes it so that fewer nutrients are actually absorbed by the body because the stomach and part of the intestinal tract are bypassed. 

This bypass of the stomach is another major difference between the two; in gastric bypass, the stomach is divided into two parts: a small gastric pouch and a larger portion of the stomach that is bypassed (known as the gastric remnant). The most popular version of gastric bypass surgery is called Roux-en-Y gastric bypass, and it involves connecting the pouch directly to the small intestine further down the digestive tract. Bypassing a significant portion of the small intestine means that fewer nutrients (and, by extension, calories) are absorbed from food. The surgeon also re-forms the bypassed section of intestine into a Y-shape so that digestive juices from the stomach and duodenum can still empty into the small intestine and aid in digestion.  

Gastric sleeve (also known as sleeve gastrectomy, or laparoscopic sleeve gastrectomy) surgery is a somewhat less complicated bariatric procedure because it doesn’t require re-routing and bypassing the small intestine. The bariatric surgeon similarly reduces the size of the stomach, but it involves actually removing about 80% of the stomach lengthwise along the greater curvature. After this is removed, the remaining stomach tissue is formed into a banana-shaped “sleeve” that is still connected to the digestive tract exactly as before. But with only 20% of the capacity left, you are unable to eat as much food as before; weight loss is realized through reduced capacity and decreased appetite.

How Much Weight Can You Lose From Gastric Sleeve & Gastric Bypass?

Both types of surgery aim to achieve weight loss results in a similar way, but through different means. Both methods are irreversible, so getting the surgery is a lifelong commitment. But because of the permanence of the procedures, they have the potential to lead to significant weight loss, especially during the first two years after the surgery. Though results vary by person, many gastric bypass patients and gastric sleeve patients report losing between 60% to 80% of excess body weight (which is defined as the amount of weight over the expected weight for someone’s age, build, and sex). 

What are the Pros and Cons of a Gastric Bypass Procedure?

Gastric bypass surgery has been around since the 1960s, so it is a well-known procedure with relatively low risk and a high chance of a patient successfully losing weight. But as with any type of surgery, it’s important to weigh the pros and cons before committing to the procedure:


  • Quick results: many patients report seeing substantial results (sometimes up to half of total weight loss) within the first six months or first year.
  • Improvement in overall health: for people who are obese, losing weight can provide a variety of benefits such as reduced high blood pressure, reduced high cholesterol, improvement in sleep apnea, and less chance of developing cardiovascular disease. Gastric bypass may even have an immediate effect on diabetes, even before significant weight loss occurs.
  • Improvement in quality of life: in addition to looking slimmer, losing weight can have a profound effect on mental health, self-esteem, and any number of other small joys.
  • Performed laparoscopically: in past decades, gastric bypass could only be performed through a major incision in the abdomen, but new medical technology means the surgery can be done laparoscopically with just a few small incisions to insert a laparoscope.


  • Surgery risk: even though mortality rates (0.1%) and complications rates (5%) are exceedingly rare, there is always some amount of risk with surgery. This can especially be a concern for morbidly obese people who may have other health conditions that make any surgery a higher risk.
  • Potential complications and side effects: these can include blood clots, infections, and gallstones.
  • Nutrient malabsorption: because of how a portion of the small intestine is bypassed, a significant amount of nutrients isn’t absorbed from digested food; as a result, gastric bypass patients must take vitamins long-term, to ensure they’re getting all the nutrients the body needs.

What are the Pros and Cons of a Gastric Sleeve Procedure?

Gastric sleeve surgery (also known as sleeve gastrectomy) is currently the most common bariatric surgery, and it is similarly low risk and effective:


  • Similar improvements to overall health as with gastric bypass.
  • Fewer complications, in part because the procedure itself is less involved, so it can be a better option for obese patients who might be more likely to develop complications as a result of surgery.
  • Though permanent, a gastric bypass can be additionally performed down the road if the doctor and patient aren’t happy with the magnitude of weight loss.
  • Malabsorption is not a problem since all ingested food still travels through the entirety of the small intestine.


  • Similar to gastric bypass, complications can arise as a result of the surgery; this can include infection if partially digested food were to “leak” out of the sutures used to form the sleeve.
  • The stomach can potentially stretch out over time and therefore reduce the effectiveness of the procedure.

Learn About Other Weight Loss Options

While both gastric bypass and sleeve gastrectomy are relatively safe ways to help people lose weight, they’re obviously not without the risk of complications. Surgery of any kind can be hard on the body, and even the small incisions associated with laparoscopy can be unpleasant and can take up to 4-6 weeks to fully heal. Moreover, most patients will not qualify for these surgeries unless their BMI (body mass index) is 40 or more, or they have medical comorbidities such as diabetes.

Fortunately, there are new weight loss options available that are lower risk, minimally invasive, and don’t require actual surgery at all. At True You, we specialize in offering these solutions as a distinct alternative to traditional surgery. With methods like Endoscopic Sleeve Gastroplasty (ESG), the ORBERA® gastric balloon, you can achieve the weight loss of bariatric surgery without the actual surgery. Or, if you’ve already had gastric bypass or sleeve gastrectomy surgery but have started to regain weight, we can also perform an endoscopic revision procedure that returns the gastric pouch or sleeve to its originally intended size. If you are interested in learning more about these weight loss procedures and how they compare to bariatric surgery, request a consultation today to speak with a weight loss professional.

Dr. Christopher McGowan
Dr. Christopher McGowan

Dr. Christopher McGowan, MD, a leader in endobariatrics, specializes in non-surgical obesity treatments and is triple-board-certified in Internal Medicine, Gastroenterology, and Obesity Medicine. Renowned for pioneering endoscopic sleeve gastroplasty (ESG) with over 2,000 procedures, his global influence and research contributions define him as a top expert.

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