Bariatric procedures for the management of severe obesity: Descriptions

INTRODUCTION — 

Obesity is a serious, chronic, and progressive disease that is associated with a significant increase in mortality and major health risks. Weight management usually starts with lifestyle modification with or without drug therapy. Patients who fail or cannot tolerate drug therapy may opt for weight-loss devices or one of several endoscopic or surgical metabolic and bariatric procedures. These interventions achieve weight loss by restricting gastric volume, altering intestinal hormones, or inducing nutrient malabsorption, thereby affecting satiety, absorption, and insulin sensitivity. Long-term success relies on combining these therapies with sustained behavioral modification. (See "Obesity in adults: Overview of management".)

This topic will review the contemporary, investigational, revisional, and obsolete metabolic and bariatric procedures offered to patients with an appropriate indication. Indications, preoperative preparation, postoperative management, complications, and outcomes of bariatric surgical procedures are described in the following topics:

●(See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

●(See "Bariatric surgery: Postoperative and long-term management".)

●(See "Bariatric surgery: Postoperative nutritional management".)

●(See "Bariatric operations: Late complications with subacute presentations".)

●(See "Outcomes of bariatric surgery".)

Individuals with obesity benefit most from multimodal therapy, which may include a combination of antiobesity medications, behavioral modifications, surgery, nutritional support, and psychological therapy. Surgery is an integral component of a multidisciplinary team that delivers comprehensive obesity care; collaboration between surgery and other disciplines impacted by obesity is essential for successful, long-term management. A reliable bariatric program should provide clear and realistic information about the potential outcomes of weight loss surgery, including associated morbidities and mortalities [1]. Proper obesity care also requires lifelong surveillance.

UTILIZATION — 

Metabolic and bariatric surgery (MBS) is one of the fastest-growing operative procedures worldwide, with approximately 696,191 operations performed in 2018 [2]. In the United States, the annual volume has remained steady at around 280,000 cases [3,4]. Between 1993 and 2016, nearly two million patients in the United States underwent bariatric surgery [5]. During this time, the field evolved from predominantly open procedures (gastric bypass or vertical banded gastroplasty) to 98 percent laparoscopic surgeries (sleeve gastrectomy or gastric bypass). As techniques improved, complication and mortality rates significantly declined from 11.7 percent and 1 percent in 1998 to 1.4 percent and 0.04 percent in 2016, respectively. Despite its proven safety and effectiveness, bariatric surgery is utilized by fewer than 1 percent of the eligible population who could benefit from it [3].

This low utilization rate is driven by several factors. The demand for bariatric surgery has likely outpaced the increase in surgical volume. Some patients can be effectively managed without surgery, while others are not suitable candidates due to behavioral or psychosocial issues. Referral bias also plays a role, as some clinicians continue to view obesity as a behavioral problem rather than a chronic disease amenable to surgical treatment, or they perceive bariatric surgery as excessively risky. Payer resistance further limits access, despite strong evidence of the surgery's cost-effectiveness. Additionally, many patients remain hesitant, fearing surgical risks, expenses, or the potential loss of enjoyment associated with eating. In some cases, they are simply unaware that surgery is a viable option for them.

MECHANISM OF WEIGHT LOSS — 

Metabolic and bariatric surgery (MBS) affects weight loss through three fundamental mechanisms: malabsorption, restriction, and the neurohormonal response that regulates hunger and energy balance (table 1). Some procedures have both a restrictive and malabsorptive component; most modern procedures also elicit a neurohormonal response in addition to restriction and/or malabsorption [1,6-12].

Restriction — Restrictive procedures promote weight loss by limiting caloric intake through a reduction in the stomach's reservoir capacity. This is achieved by resection, bypass, the use of space-occupying devices such as balloons, or the creation of a gastric outlet obstruction.

Sleeve gastrectomy (SG) has become the leading restrictive procedure, largely due to its hormonal effects on hunger regulation. In contrast, endoscopic procedures such as intragastric balloon placement, the transpyloric shuttle, and aspiration therapy also reduce food intake but result in more gradual and modest weight loss. These less-invasive approaches are associated with higher recidivism rates compared with contemporary surgical procedures.

Vertical banded gastroplasty and laparoscopic adjustable gastric banding are purely restrictive procedures that rely solely on reducing stomach size to limit solid food intake, leaving the small intestine's absorptive function intact. Unlike SG, they do not influence the hormonal response to eating, making them less effective for sustained weight loss. In contemporary practice, these procedures have largely fallen out of favor due to limited long-term efficacy and high complication rates.

Malabsorption — Malabsorptive procedures promote weight loss by reducing the small intestine's functional absorptive capacity. This is achieved by either bypassing segments of the small bowel or diverting biliopancreatic secretions that aid in nutrient absorption. The extent of weight loss depends on the remaining length of the functional small bowel. Jejunoileal bypass and biliopancreatic diversion (BPD) are examples of malabsorptive procedures. However, while these operations can result in profound weight loss, their benefits are often outweighed by severe metabolic complications, including protein-calorie malnutrition and various micronutrient deficiencies. Due to these risks, both jejunoileal bypass and BPD have been abandoned.

Combination of restriction and malabsorption — Established procedures such as Roux-en-Y gastric bypass (RYGB), BPD with duodenal switch, and single-anastomosis duodenoileal bypass with sleeve gastrectomy combine both restrictive and malabsorptive mechanisms. In RYGB, a small gastric pouch limits oral intake, while the small bowel reconfiguration promotes additional weight loss through dumping physiology, favorable hormonal changes, and mild malabsorption. The procedure also reduces hunger, likely due to its hormonal effects. Less common procedures, including one-anastomosis gastric bypass and single-anastomosis duodenoileal bypass, similarly induce weight loss through a combination of restriction and malabsorption.

All these procedures trigger hormonal changes that enhance satiety and reduce hunger, although the precise mechanisms behind these effects remain unclear.

PROCEDURES ENDORSED BY THE ASMBS — 

The American Society of Metabolic and Bariatric Surgery (ASMBS) publishes and maintains a list of bariatric procedures that it endorses on its website. Centers accredited by the American College of Surgeons Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) may perform the following procedures without institutional review board approval.

In 2022, the ASMBS estimated that 280,000 bariatric procedures were performed in the United States, including 57.1 percent sleeve gastrectomy (SG); 22.2 percent Roux-en-Y gastric bypass (RYGB); 2.2 percent biliopancreatic diversion with duodenal switch (BPD/DS); 1.6 percent intragastric balloon (IGB) and endoscopic sleeve gastrectomy each; and <1 percent adjustable gastric banding (AGB), one-anastomosis gastric bypass (OAGB), and single-anastomosis duodenoileal bypass with sleeve gastrectomy (SADI-S) each [4].

Sleeve gastrectomy — SG was initially offered to patients with super severe obesity (body mass index [BMI] >60 kg/m²) as a bridge procedure to a more technically challenging RYGB, BPD, or SADI-S [13-15]. It is now a single-stage primary operation [16]. Since 2016, it has been the most commonly performed bariatric procedure in the world and in the United States [17,18].

SG is technically easier to perform than the RYGB as it does not require multiple anastomoses. It is also safer as it reduces the risks of internal herniation and protein and micronutrient malabsorption [19,20]. In one meta-analysis, SG was associated with a decreased risk of all-cause mortality during follow-up compared with RYGB [21].

Description of SG — SG is a partial gastrectomy in which the majority of the greater curvature of the stomach is removed and a tubular stomach is created (figure 1 and image 1). The antrum is divided approximately 2 to 6 cm away from the pylorus, and a sleeve is created around a 32 to 40 French bougie [22]. (See "Obesity: Genetic contribution and pathophysiology".)

The laparoscopic approach to an SG can be found at the following link to the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) video library's page on SG for morbid obesity.

The techniques of laparoscopic SG are covered in more detail in their own topic. (See "Laparoscopic sleeve gastrectomy".)

Weight loss mechanism of SG — SG is a restrictive procedure by permanently removing about 75 percent of the stomach; the remaining tubular stomach is small in its capacity and resistant to stretching due to the absence of the fundus. Furthermore, gastric motility changes also occur with surgery and may affect weight loss outcomes [23,24].

The hormonal changes that occur after SG indicate that its success is not only due to restricted food intake. SG removes the fundus of the stomach, which contains most of the ghrelin-producing cells. Ghrelin levels decrease [9] and glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) levels increase, promoting less hunger [25], while insulin resistance improves and aids glycemic control [26].

Expected weight loss from SG — At two years, the expected weight loss is approximately 25 to 30 percent of a patient's total body weight [27-29].

Adverse effects of SG — SG will make the stomach a high-pressure organ with a sphincter at both ends. Consequently, leaks are more frequent after SG than RYGBs, and more difficult to manage [30]. Additionally, the SG has a much higher incidence of gastroesophageal reflux disease (GERD) because of its higher-pressure nature [31]. Severe GERD or Barrett esophagus is a relative contraindication to SG; such patients should consider RYGB instead. (See "Laparoscopic sleeve gastrectomy", section on 'Indications'.)

Roux-en-Y gastric bypass — In the 1990s to early 2000s, RYGB was the gold standard and the most performed bariatric surgery worldwide, especially in the United States and Europe. It was surpassed by SG around 2014 to 2016. Nevertheless, it remains one of the most commonly performed bariatric procedures.

Description of RYGB — The RYGB is characterized by a small (approximately 30 mL) proximal gastric pouch that is divided and separated from the distal stomach and anastomosed to a Roux limb of small bowel that is 75 to 150 cm in length (figure 2) [32,33]. This gastrojejunal anastomosis aims to be about 15 to 20 mm.

The small intestine is divided at a distance of 50 to 150 cm distal to the ligament of Treitz. By dividing the bowel, the surgeon creates a proximal biliopancreatic limb that transports the secretions from the gastric remnant, liver, and pancreas. The Roux limb (or alimentary limb) is anastomosed to the new gastric pouch and functions to drain consumed food. The cut end of the biliopancreatic limb and the Roux limb are then connected 75 to 150 cm distally from the gastrojejunostomy. Major digestion and absorption of nutrients then occurs in the resultant common channel, where pancreatic enzymes and bile mix with ingested food. The ideal Roux limb, biliopancreatic limb, and common channel length have not been determined. (See 'RYGB revisions' below.)

The techniques of laparoscopic RYGB are covered in more detail in their own topic. (See "Laparoscopic Roux-en-Y gastric bypass", section on 'Technique'.)

Weight loss mechanism of RYGB — RYGB works by restricting the amount of food one ingests (restriction), by limiting the amount of nutrients absorbed from the ingested food (malabsorption), and by altering the hormonal response to food.

●Restriction – The small gastric pouch (30 mL) and the narrow anastomotic outlet (15 to 20 mm) serve to restrict caloric intake.

●Malabsorption – The jejunal Roux limb connects directly to the gastric pouch, thus bypassing most of the stomach, the duodenum, and the first portion of the small intestine, which are key to absorption of iron, calcium, and certain micronutrients (eg, vitamin B12). The Roux-en-Y anatomy also causes food to enter the jejunum without first mixing with bile and pancreatic enzymes proximal to the distal anastomosis/common channel, further reducing the efficiency of fat, protein, and micronutrient absorption. The optimal length of the Roux limb in achieving the best balance between weight reduction and complications of malabsorption is controversial [34]. Others believe that the length of the biliopancreatic limb determines the best results for metabolic changes and weight loss without malabsorption complications [35,36]. In general, RYGB causes less severe malabsorption than BPD/DS and SADI-S.

●Hormonal – Gut hormones also have a role in the weight loss seen following RYGB.

•Gastrojejunostomy anatomy (connection between the stomach pouch and jejunum) is associated with dumping physiology and causes unpleasant symptoms of lightheadedness, nausea, diaphoresis and/or abdominal pain, and diarrhea when a high-sugar meal is ingested [37]. This response may serve as a negative conditioning response against the consumption of a high-sugar diet postoperatively.

•Ghrelin is a peptide hormone secreted in the foregut (stomach and duodenum) that stimulates the early phase of meal consumption. The normal pulsatile release of this orexigenic (appetite-producing) hormone appears to be inhibited by the RYGB configuration [6-8]. The reduced ghrelin levels may contribute to the characteristic loss of appetite seen in post-RYGB patients. An exaggerated response of PYY may also contribute to the loss of appetite [8]. Reduced ghrelin levels may eventually increase to their preoperative levels [38]. (See "Obesity: Genetic contribution and pathophysiology".)

•Hormones such as GLP-1 and cholecystokinin, which are increased after RYGB, may promote an anorectic state [38]. (See "Glucagon-like peptide 1-based therapies for the treatment of type 2 diabetes mellitus" and "Physiology of cholecystokinin".)

Expected weight loss from RYGB — The expected loss of total body weight after two years is approximately 30 to 35 percent [39].

Adverse effects of RYGB — RYGB is contraindicated in patients with short bowel, severe malnutrition, or prior major gastric surgery. In general, RYGB and SG have similar major complication rates, but RYGB is associated with more minor complications than SG [40]. Both have fewer complications than BPD/DS but more complications than AGB. (See "Metabolic and bariatric operations: Early morbidity and mortality".)

Because RYGB involves two gastrointestinal anastomoses, it may be riskier for patients who chronically take glucocorticoid or nonsteroidal anti-inflammatory medications because of the risk of leaks or marginal ulceration. Crohn disease, in particular, is a relative contraindication for RYGB due to the potential for strictures and leaks at the anastomoses [41]. Patients who have obesity and are candidates for a renal or liver transplant may be better suited for an SG because of their need for anti-inflammatory or antirejection medication [42]. (See "Laparoscopic Roux-en-Y gastric bypass", section on 'Indications'.)

One-anastomosis gastric bypass — The OAGB is a modification of the loop gastric bypass and is technically easier to perform than an RYGB because it requires only one anastomosis. It is also referred to as the mini-gastric bypass. Outside of the United States, OAGB is a popular operation, with an estimated 30,000 procedures done annually (third-most performed) worldwide [43]. It has been endorsed by the ASMBS as a primary procedure in 2022 [44,45].

Description of OAGB — The OAGB is usually performed laparoscopically and includes the division of the stomach starting 1 to 2 cm distal mid-stomach, extending cephalad to the angle of His, following a 36 to 38 French luminal tube placed along the lesser curvature (figure 3). This subsequent pouch is anastomosed to a loop of jejunum as an antecolic and antegastric loop gastrojejunostomy [46]. Most studies used a 150 to 200 cm biliopancreatic limb distal to the ligament of Treitz to create the afferent limb. In the Carbajo modification (lateral-lateral gastrojejunostomy), the afferent loop is sutured to the gastric pouch staple line above the anastomosis, and the apex of the loop is sutured to the bypassed stomach to divert the flow of bile away from the gastric pouch [47].

Weight loss mechanism of OAGB — The OAGB combines restrictive as well as malabsorptive properties for weight loss [46,48,49]. Though not extensively studied, there are likely hormonal changes that occur such that insulin sensitivity improves and hunger is abated because the distal stomach and proximal small intestine are bypassed.

Expected weight loss from OAGB — Weight loss outcomes after OAGB appear to be comparable with those of RYGB and SG, with most series reporting a 32 percent total weight loss at up to five-year follow-up and a 30 percent total weight loss at up to 15-year follow-up [44].

A number of studies have shown that the metabolic effect of OAGB on type 2 diabetes is similar or superior to RYGB and SG, with remission rates >80 percent reported in large prospective studies [44,50]. At 10 and 15 years, 74 percent and 67 percent of those who followed up remained in complete remission of diabetes, respectively [51].

Adverse effects of OAGB — Compared with RYGB, OAGB requires shorter mean operative time but comparable hospital length of stay [52]. Otherwise, the incidence of leaks, marginal ulcers, dumping syndrome, bowel obstruction, revisions, and mortality was all similar.

Reported early complications of OAGB include nausea/vomiting, anastomotic leak (1 percent), hemorrhage, wound infection, and death (0.1 percent). Long-term complications after OAGB include marginal ulceration (2.7 percent), bile reflux, steatorrhea, malabsorption, protein calorie malnutrition (0.7 percent), excessive weight loss, gastro-gastric fistula, and internal herniation [53].

Because of the loop reconstruction, there is a concern for the high rates of alkaline bile reflux [54,55]. The reported incidences of bile reflux ranged widely from 0.9 to 30 percent [44,56]. If the bile reflux becomes severe enough, a conversion to an RYGB is used as a rescue procedure. An associated risk of bile reflux is the development of esophageal or gastric cancer [57]. However, systematic reviews of actual cancer cases after OAGB have not validated this concern [58].

Biliopancreatic diversion with duodenal switch — BPD/DS, a modified BPD, reduces marginal ulceration, dumping, severe malabsorption, and diarrhea seen in the now-abandoned original BPD. It profoundly impacts fat metabolism, often achieving near-complete remission of type 2 diabetes and lipid disorders.

In the United States, the role of BPD/DS is not clear. Because it maximizes malabsorption of calories and fat, BPD/DS leads to greater weight loss and diabetes control than RYGB and SG [59-62]. Some surgeons perform this procedure for patients with a BMI >50 kg/m² [63], while others reserve it as a revisional procedure for failure to lose weight or weight recidivism after other procedures. Because BPD/DS is a technically difficult operation with a high complication rate, it has not been fully embraced by all bariatric surgeons. Although complex, BPD/DS can be performed laparoscopically by experienced surgeons [64,65].

Description of BPD/DS — The BPD/DS procedure involves creating an SG with preservation of the pylorus and creation of a Roux limb with a short common channel of about 150 to 200 cm (figure 4). The BPD/DS procedure differs from the BPD in the portion of the stomach that is removed, as well as in the preservation of the pylorus, like an SG, and prevents dumping syndrome (a major issue in RYGB). The duodenal switch also allows more forward flow of the contents of the biliopancreatic limb and avoids the complications of stasis that plagued the jejunoileal bypass [66,67]. It is associated with a lower incidence of stomal ulceration and diarrhea than with BPD alone.

Weight loss mechanism of BPD/DS — BPD/DS is a combination of restrictive and malabsorptive weight loss mechanisms. Though less studied than the hormone responses for the SG and RYGB, there is most likely some contribution of altered hormone production to sustained weight loss. For example, ghrelin appears to be suppressed after a BPD/DS [68]. The contribution of gut hormones to weight loss and insulin sensitivity with a BPD/DS is largely unknown.

Expected weight loss from BPD/DS — BPD/DS is widely associated with the greatest weight loss and remission of diabetes among all currently performed bariatric operations and procedures [69]. At two years, the expected weight loss is 40 percent or greater of total body weight [39].

Adverse effects of BPD/DS — However, BPD/DS also has the highest surgical and nutrition complication rate of all bariatric operations [70]. Its use has been limited by the high rates of protein malnutrition, anemia, diarrhea, and stomal ulceration [39,66]. The rate of malnutrition was 8.3 percent after BPD/DS, with 5.4 percent requiring revisional surgery for malnutrition and 24.6 percent requiring cholecystectomy for gallbladder diseases [63].

Single-anastomosis duodenoileal bypass with sleeve gastrectomy — SADI-S is a simplified variant of the BPD/DS operation [71]. The SADI-S procedure was developed in part to reduce the complexity and risks of BPD/DS (ie, performing a Roux-en-Y configuration with small-diameter distal bowel and a need for two anastomoses). SADI-S has been endorsed by the ASMBS as an appropriate primary or revisional metabolic bariatric procedure [69,72].

Description of SADI-S — After an SG is created, the duodenum is divided about 4 cm from the pylorus. A single anastomosis is then created between the side of the first or second part of the duodenum and the distal jejunum/proximal ileum, creating an afferent limb of biliopancreatic fluid and an efferent limb that acts like a common channel (figure 5). Most contemporary publications on SADI-S use a common channel length of no less than 300 cm, which makes the afferent limb length variable [71]. SG sizes also vary widely, from 34 to 54 French, though most bariatric surgeons will make an SG that is more generous to avoid high-pressure lumens that can cause reflux and perpetuate leaks [73].

Weight loss mechanism of SADI-S — The weight loss occurs due to restrictive, malabsorptive, and hormonal mechanisms.

Expected weight loss from SADI-S — There are still limited long-term data available for single anastomosis duodenal switch. In the absence of published prospective randomized trials, the best estimate of total weight loss two years after SADI-S is between 35 to 40 percent [69,73-76]. In nonrandomized comparative studies, SADI-S achieved similar percent excess weight losses compared with RYGB [77], SG [78], and BPD/DS [79,80].

Adverse effects of SADI-S — SADI-S patients had fewer anastomotic complications, bowel obstructions, internal hernias, and volvulus, presumably because SADI-S required one fewer anastomosis than RYGB and BPD/DS [81]. SADI-S, however, was associated with a greater risk of chronic diarrhea, even with a 300 cm common channel. With a common channel length of less than 300 cm, the rates of malnutrition were very high. It is not clear why a BPD/DS can have a common channel of 150 to 200 cm but the SADI-S does better with a 300 cm common channel.

Intragastric balloon — IGB therapy is an option for patients with a BMI of >27 kg/m² in Europe or >30 kg/m² in the United States who have tried and failed previous attempts at weight management with lifestyle changes alone. It remains open whether IGB therapy should be used alone, sequentially, with concomitant therapies, as a bridge to bariatric surgery, or as a bridge to other surgeries such as hernia repair or organ transplant [82]. Balloon placement is contraindicated in patients who have had previous gastric surgery or who have large hiatal hernias (>5 cm) [83]. (See "Intragastric balloon therapy for weight loss", section on 'Indications'.)

Description of IGB — The IGB consists of a soft, saline- or gas-filled balloon that promotes a feeling of satiety and restriction (figure 6) [84]. Commercially available IGB systems vary by design, material, insertion/extraction methods, volume, and maximal duration of treatment (table 2). Two IGB devices, Orbera and Obalon balloons, have been approved by the US Food and Drug Administration (FDA). Other IGB systems are commercially available in various regions and countries but have not received FDA approval in the United States.

IGB therapy for weight loss is discussed in detail in its own topic. (See "Intragastric balloon therapy for weight loss".)

Weight loss mechanism of IGB — The weight loss mechanism of IGB therapy is by restriction and likely by a change in gut motility (ie, delayed gastric emptying).

Expected weight loss from IGB — IGBs can produce 6 to 15 percent total body weight loss initially [85,86]. However, they are temporary measures, and weight regain is expected after their removal [87].

Adverse effects of IGB — Adverse events include nausea, vomiting, reflux, balloon migration, balloon intolerance, balloon leak, and intestinal or stomach perforation. IGBs are typically filled with blue-dyed saline. If the patient's urine turns blue or green, then a balloon leak should be suspected. Patients should seek immediate medical attention as the balloon would then be at risk for migrating and causing an intestinal obstruction. It is also essential that IGBs are not kept beyond the manufacturer's suggested maximal duration of therapy, beyond which time the leak rate increases significantly. (See "Intragastric balloon therapy for weight loss", section on 'Serious adverse events'.)

OTHER FDA-APPROVED DEVICES — 

There are several other procedures in various stages of acceptance due to efficacy and availability. Most do not achieve the weight loss success of the aforementioned operations (with the exception of the intragastric balloon [IGB], as these procedures are equivalent); however, some procedures have shown much greater promise than others. As such, there can be a niche for these procedures who are poor operative candidates, in those who need a better body mass index (BMI) for other procedures, or in those with hostile abdomens. They can even be considered as prehabilitation for patients with extremely high BMIs (>60 kg/m2), making them better operative candidates for a more permanent procedure. These procedures, thus, are part of the surgical armamentarium for treating obesity.

Endoscopic gastric remodeling — Endoscopic gastric remodeling (EGR) is an endoscopic, luminal version of the sleeve gastrectomy. It may be performed using the Overstitch Endoscopic Suturing System (as endoscopic sleeve gastrectomy [ESG] or endoscopic gastric plication), Incisionless Operating Platform (as primary obesity surgery endoluminal [POSE] procedure), or Endomina System.

EGR may be performed as an adjunct to lifestyle modification in patients with a BMI >30 or from 27 to 29.9 kg/m² with comorbidities [88,89]. EGR is approved by the US Food and Drug Administration (FDA), and the American Medical Association has recognized it as an effective procedure with its own Current Procedural Terminology code, indicating its acceptance as a bariatric procedure. The choice of device is based on clinical context, patient values, availability, and operator experience, as there is insufficient evidence to recommend one device over another.

Description of EGR — Two techniques of EGR exist:

●ESG uses full-thickness bites of sutures placed endoscopically to plicate the anterior and posterior walls of the stomach. The first technique uses several running sutures to plicate the greater curvature of the stomach in a "U" shape [90,91].

●POSE places three circular sets of plications: two near the incisura, and one at the fundus-body juncture [92]. The circular plications are designed to limit gastric expansion during meals. Additional vertically arranged plications along the gastric body are then placed to further restrict the stomach.

Weight loss mechanism of EGR — The mechanism for weight loss appears to be purely restrictive. All EGR procedures reduce the width and length of the stomach and are believed to delay gastric emptying and early satiety without inducing hormonal effects [89,93].

Expected weight loss from EGR — According to several systematic reviews and meta-analyses, the pooled total weight loss at 12 months was 10.5 percent in randomized trials and 17.3 percent in observational studies [88,89]. In nonrandomized comparative studies, total body weight loss achieved with ESG is significantly less than that achieved with laparoscopic sleeve gastrectomy (LSG; 19.1 versus 28.9 percent) [94]. For studies with follow-up of two and three years, most reported that the initial weight loss achieved by ESG was sustained [94-97].

Adverse effects of EGR — Mild gastrointestinal symptoms such as nausea, vomiting, and abdominal pain are common after EGR, but all typically resolve within seven days. Serious adverse events, such as bleeding or abscess formation, occurred in 2 to 3 percent of patients across most studies [88,89]. There is a trend toward fewer overall complications compared with LSG (relative risk 0.51, 95% CI 0.23-1.11); new onset gastroesophageal reflux disease developed in <3 percent of those who underwent ESG, which is less common than after LSG (1.3 versus 17.9 percent) [94]. The outcomes of the ESG beyond two years are not known.

Transpyloric shuttle — The transpyloric shuttle (TPS) is a gastric device that is endoscopically placed into the distal stomach meant to block the pylorus and prevent food from moving into the duodenum. The TPS has received FDA approval in the United States but has not yet been commercialized.

Description of TPS — During ingestion of food, it is propelled forward by peristalsis to the pylorus, and it becomes lodged in the pylorus, making the patient feel full (figure 7) [98]. The mechanism of action is related to the device causing intermittent gastric outlet obstruction with the larger portion of the device, bobbing between the antrum and pylorus with gastric contractions. Unlike the IGB, it is not a space-occupying device. Because the larger portion of the device is filled with silicone, it does not have a risk of deflation and has FDA approval for 12 months of dwell time.

Weight loss mechanism of TPS — The TPS system works by restriction and delaying gastric emptying to make the patient feel satisfied.

Expected weight loss from TPS — To date, only one randomized trial has been reported in abstract form [99]. A United States multicenter randomized sham-controlled trial demonstrated greater total weight loss with TPS than sham control (9.5 versus 2.8 percent). An early report had the percent total body weight loss at six months to be about 14.5 percent [98]. Larger studies are reported in the making, but have yet to be published [100].

Adverse effects of TPS — In the United States pivotal trial, the TPS was generally well tolerated, while 2.8 percent of patients had a serious adverse event, these being mostly shuttle impaction. However, long-term complications are not known since very few patients have undergone the TPS treatment.

OTHER WEIGHT LOSS PROCEDURES

Endoscopic gastrointestinal bypass devices — A barrier device is deployed to prevent luminal contents from being absorbed in the proximal small intestine. It is primarily used to treat patients who have both diabetes and obesity in conjunction with lifestyle modification.

Currently, no barrier device is US Food and Drug Administration (FDA) approved. Only a duodenal-jejunal barrier liner (DJBL) has been tested in randomized trials. In two small trials, the use of a DJBL resulted in a 5.4 percent greater total weight loss and 0.73 percent greater decrease in hemoglobin A1c than lifestyle modification alone [101,102]. In observational studies, DJBL was associated with 18.9 percent total weight loss (95% CI 7.2-30.6) after a longer implantation period [103]. The safety profile of DJBL appears to be acceptable, with a 15.7 percent serious adverse event rate and with <1 percent of patients requiring surgical intervention to address adverse events.

Laparoscopic gastric plication — Similar to endoscopic sleeve gastrectomy (ESG), laparoscopic gastric plication (LGP) forms a gastric sleeve without requiring resection. Unlike ESG, however, LGP is done laparoscopically and does not require special endoscopic equipment; the gastric sleeve is formed by plicating the greater curvature to itself to reduce the lumen of the stomach.

Compared with laparoscopic sleeve gastrectomy, LGP appears to have worse long-term outcomes (eg, weight loss, diabetes resolution), more complications, and similar operating time and length of hospital stay [104,105]. Thus, it is doubtful at this point that the LGP will become a meaningful metabolic and bariatric operation.

Bariatric arterial embolization — This endovascular approach promotes weight loss by embolizing the left gastric artery to induce localized ischemia in the gastric fundus, which in theory modulates the endocrine functions to suppress appetite. Multiple studies have demonstrated appetite suppression and weight loss (8 percent total body weight; 11 to 17 percent excess body weight at one year) with a favorable safety profile [106].

Although there is a benefit over diet and lifestyle modifications, bariatric arterial embolization does not approach the weight loss efficacy of other bariatric surgeries [107], but it appears to be as effective as many available weight loss medications [108]. It remains an investigational procedure.

REVISIONAL PROCEDURES

AGB revisions — Nearly half of the patients who undergo adjustable gastric banding (AGB) require revision surgery due to insufficient weight loss or other complications [109]. For such patients, the band can be replaced, or it can be converted to a sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), or biliopancreatic diversion with duodenal switch (BPD/DS) [110]. The timing of the revision can be important, as the gastric tissue may be inflamed or fibrotic due to the band. As a result, some authors have advocated a staged approach [111]. The band is first removed, and then, after a period of 8 to 12 weeks, the stomach is converted to another bariatric procedure.

RYGB revisions — Weight recidivism is a common problem following RYGB surgery. On average, patients regain between 20 and 30 percent of their lost weight, while one-third of patients experience excessive weight gain (defined as ≥25 percent of total lost weight) [112].

While most people who experience weight recidivism after RYGB because the initial procedure was not effective or they are unable to adhere to a healthy lifestyle, there are some anatomical reasons that an RYGB might fail. Over time, the patient may lose the sense of restriction if their gastric pouch enlarges, a fistula occurs between the gastric pouch and the remnant stomach that would accommodate more food intake, or the anastomosis between the gastric pouch and the Roux limb enlarges, typically to greater than 20 mm.

These conditions may be an indication to recreate the gastric pouch and gastrojejunal anastomosis [113,114], or to revise the jejunojejunostomy anastomosis. Alternatively, RYGB can be converted to a different bariatric procedure. The indication to operate for weight regain has the same body mass index requirement as primary bariatric operations. (See "Bariatric surgery for management of obesity: Indications and preoperative preparation", section on 'Indications'.)

●The endoscopic approach to gastrojejunal anastomotic revision, transoral outlet reduction (TORe), is a US Food and Drug Administration (FDA)-approved minimally invasive treatment that aims to reduce the diameter of the gastrojejunal anastomosis, delaying gastric emptying and increasing satiety [115]. Total body weight loss of 8.5 percent at one year, 6.9 percent at three years, and 8.8 percent at five years after TORe has been shown [116]. TORe is also an effective treatment for refractory dumping symptoms after RYGB. In one study, 88 and 85 percent of patients had resolution of dumping symptoms at one month and three years, respectively, after TORe [117].

●The concept of "distalization," or revising the jejunojejunostomy anastomosis to make the biliopancreatic limb longer, has gained some traction. For these patients, there are no issues with the gastric pouch, but they have regained a significant amount of weight. The biliopancreatic limb is lengthened without sacrificing too much of the common channel. This has led to some positive results for renewed weight loss and comorbidity control [118].

●Alternatively, the RYGB can be converted to another bariatric procedure. The choice of procedures is not standardized and depends on individual anatomy and risk factors [119]. As an example, the laparoscopic conversion of a failed RYGB to a BPD/DS can be found on the following link to the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) video library's page on laparoscopic conversion of RYGB to biliopancreatic diversion with duodenal switch.

SG revisions — One criticism of the SG was the durability of the operation, as one theorized that, over time, the SG could expand and patients would lose their restriction. In a French database study of 224,718 patients who underwent SG, the rate of revision surgery was 4.7, 7.5, and 12.2 percent, at 5, 7, and 10 years, respectively [120]. The main reasons for revision surgery were persistence of obesity, recurrence of diabetes [121], and intractable symptoms of gastroesophageal reflux disease [122]. The most common revision procedure was RYGB (75.2 percent), followed by re-SG (18.7 percent) [120].

RARELY PERFORMED PROCEDURES

Adjustable gastric banding — Adjustable gastric banding (AGB) is a purely restrictive procedure that compartmentalizes the upper stomach by placing a tight, adjustable prosthetic band around the entrance to the stomach. It is most commonly performed laparoscopically.

AGB is performed less often in contemporary bariatric practices, declining from 24 percent of all bariatric procedures in 2003 to 0.9 percent in 2019 [17,18]. The decline may be due to its relatively modest amount of expected weight loss, coupled with high rates of revision and weight recidivism [17,109]. It has been gradually replaced by other bariatric surgical procedures, especially SG, which offers better results for weight loss and comorbidity resolution [123]. However, over 160,000 bands have been placed during the last decade, and AGB is still performed at some centers [124].

Description of AGB — The gastric band consists of a soft, locking silicone ring connected to an infusion port placed in the subcutaneous tissue (figure 8). The port may be accessed with relative ease by a syringe and needle (figure 9). Injection of saline into the port leads to a reduction in the band diameter, resulting in an increased degree of restriction. The band is adjustable and is placed laparoscopically [125,126]. The goal of band adjustments is to give the patient a restriction of approximately one cup of dried food and satiety for at least 1.5 to 2 hours after a meal.

The laparoscopic approach to the placement of a gastric band can be found at the following link to the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) video library's page on laparoscopic adjustable gastric band placement.

Weight loss mechanism of AGB — AGB is a purely restrictive procedure. The amount of restriction can be modified over time, and it allows increased restriction to occur if the patient requires it.

Expected weight loss from AGB — AGB results in an approximate 10 to 15 percent total weight loss at one to five years after surgery [127].

Adverse effects of AGB — Vomiting, regurgitation, reflux with saliva, dysphagia, and food intolerances are common complications early after AGB that may delay diet progression or lead to maladaptive eating behaviors [124]. The 30-day rate of major adverse events after AGB is 2.9 percent [127].

Band removal is the best treatment option for long-term complications such as band slip/gastric prolapse, gastroesophageal reflux disease, and esophageal dilatation. In a 15-year study of AGB, there has been a notable need for additional surgery due to late adverse events, with nearly half of the patients requiring one or more revisional procedures during the follow-up period [109]. (See 'AGB revisions' above.)

OBSOLETE PROCEDURES — 

The following procedures are obsolete and no longer performed.

Jejunoileal bypass — The jejunoileal bypass was one of the first bariatric operations, performed initially in 1969 (figure 10) [128,129]. It has since been abandoned due to the high complication rate and frequent need for revisional surgery. Its importance lies in the care of surviving patients who have undergone this procedure. Although excess weight loss was excellent, jejunoileal bypass was associated with multiple complications, such as liver failure (up to 30 percent), death, diarrhea, electrolyte imbalances, oxalate renal stones, vitamin deficiencies, malnutrition, and arthritis [130-134].

The procedure was performed by dividing the jejunum close to the ligament of Treitz and connecting it a short distance proximal to the ileocecal valve, thereby diverting a long segment of small bowel, resulting in malabsorption.

Patients who have undergone this procedure should be monitored closely for complications (particularly liver disease) and undergo reversal if such complications arise. (See "Bariatric operations: Late complications with subacute presentations".)

Vertical banded gastroplasty — A gastroplasty narrows the area of food passage between the proximal and distal stomach. This procedure did not result in significant weight loss, and the vertical banded gastroplasty (VBG) was subsequently created to put a more permanent restrictive barrier between the proximal and distal stomach [135].

VBG is a purely restrictive procedure in which the upper part of the stomach is partitioned by a vertical staple line with a tight outlet wrapped by a prosthetic mesh or band (figure 11). The small upper stomach pouch fills quickly with solid food and prevents the consumption of a large meal. Weight loss occurs because of decreased caloric intake of solid food. Patients who have undergone VBG can be expected to have excess weight loss of 58 percent [136]. The effectiveness of such a restrictive mechanism depends upon the durability of the pouch and the stoma (outlet) size. Ingestion of high-calorie liquid meals and gradually increased pouch capacity due to overeating have been some of the major causes of its failure. Sweets eaters who rely on soft meals (ie, ice cream, milk shakes) do not benefit significantly from this procedure [137].

VBG has been replaced largely by other procedures and is rarely performed due to a lack of sustained/desired weight loss, as well as the high incidence of complications requiring revision (20 to 56 percent) [137-142]. The majority of revisions are required for staple line disruption, stomal stenosis, band erosion, band disruption, pouch dilatation, vomiting, and gastroesophageal reflux disease. (See "Bariatric operations: Late complications with subacute presentations".)

Vagal blockade — The abdominal vagal nerve controls gastric emptying and signals the satiety center in the brain. A surgically implanted device that sends intermittent electrical pulses to the abdominal vagal nerve has been approved by the US Food and Drug Administration (FDA) as a possible treatment for obesity, but this system is not currently commercially available.

Aspiration therapy — Aspiration therapy induces weight loss by removing a portion of ingested caloric intake after each meal via a modified percutaneous endoscopic gastrostomy tube system. An example of aspiration therapy, the AspireAssist, was FDA approved but withdrawn from the market for financial reasons in 2022.

SUGGESTIONS FOR CHOOSING A BARIATRIC PROCEDURE FOR PATIENTS — 

In deciding which procedure to offer, surgeons must consider the patient's desire as well as their physiology, their current body mass index (BMI), their comorbidities, and what the desired outcome is. As examples:

●Patients who have severe gastroesophageal reflux disease (GERD) and esophagitis may not do as well with a sleeve gastrectomy (SG). By contrast, Roux-en-Y gastric bypass (RYGB) is a good treatment option for GERD in individuals with obesity.

●Patients with difficult-to-control type 2 diabetes mellitus will likely do better with a biliopancreatic diversion with duodenal switch (BPD/DS), a single-anastomosis duodenoileal bypass with sleeve gastrectomy (SADI-S), or a RYGB with a long biliopancreatic limb.

●Patients with a BMI >50 kg/m² need more weight loss, and thus, may do better with a BPD/DS or a SADI-S.

●Patients with a BMI >60 kg/m² or who are at high cardiopulmonary risk for surgery may do better with a staged approach. Initially, these patients would get an SG followed by an SADI-S, RYGB, a BPD/DS, or a one-anastomosis gastric bypass (OAGB) a year later after some improvement in their cardiopulmonary profile and some weight loss. They may be too sick for a procedure that might take three to four hours in a single setting.

●Patients who are candidates for organ transplant will likely do better with an SG as there is less concern for being on chronic immunosuppression after the transplant.

●In patients with very complex abdominal wall hernias, an SG may be a better option because the dissection needed to create a Roux or biliopancreatic limb may be extensive and lead to enterotomies. In these patients, it may even be better to do an endoscopic SG to avoid additional surgery before undertaking a complex hernia repair with a component separation.

There are also some important randomized controlled trials to consider [143]:

●The SLEEVEPASS trial compared the SG with the RYGB and showed that the percent total body weight loss at 10 years was superior for the RYGB, with similar outcomes for the comorbidities [144]. (See "Outcomes of bariatric surgery", section on 'RYGB and SG'.)

●The YOMEGA trial showed that OAGB and RYGB resulted in similar weight loss and comorbidity resolution, but more patients who underwent OAGB developed GERD (41 versus 18 percent) [145].

●A randomized trial comparing SG with OAGB showed that OAGB was superior in weight loss, quality of life, and comorbidity resolution at seven years [146].

Regardless of the procedure chosen, it is important for the bariatric surgeon, the rest of the team, and even referring providers to emphasize to the patient that medications and surgery are complementary rather than mutually exclusive. It is equally important for the patient to understand that surgery is only one aspect of obesity management, and that maintaining a healthy lifestyle (which includes a nutritional plan, regular activity, and adequate sleep), seeking psychiatric help, and taking necessary medications to prevent obesity recurrence, when necessary, after surgery will go a long way towards long-term weight maintenance.

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bariatric surgery".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Weight loss surgery (The Basics)")

●Beyond the Basics topics (see "Patient education: Losing weight (Beyond the Basics)" and "Patient education: Weight loss surgery and procedures (Beyond the Basics)")

SUMMARY

●Mechanism of weight loss – Metabolic and bariatric surgery (MBS) affects weight loss through three fundamental mechanisms: malabsorption, restriction, and the neurohormonal response that regulates hunger and energy balance. Some MBS procedures (eg, sleeve gastrectomy [SG]) are purely restrictive, while others (eg, Roux-en-Y gastric bypass [RYGB]) are both restrictive and malabsorptive, while most procedures also elicit a neurohormonal response on eating (table 1). (See 'Mechanism of weight loss' above.)

●ASMBS-endorsed procedures – The following MBS procedures are endorsed by the American Society of Metabolic and Bariatric Surgery (ASMBS) (see 'Procedures endorsed by the ASMBS' above):

•Sleeve gastrectomy (see 'Sleeve gastrectomy' above and "Laparoscopic sleeve gastrectomy")

•Roux-en-Y gastric bypass (see 'Roux-en-Y gastric bypass' above and "Laparoscopic Roux-en-Y gastric bypass")

•One-anastomosis gastric bypass (see 'One-anastomosis gastric bypass' above)

•Biliopancreatic diversion with duodenal switch (see 'Biliopancreatic diversion with duodenal switch' above)

•Single-anastomosis duodenoileal bypass with sleeve gastrectomy (see 'Single-anastomosis duodenoileal bypass with sleeve gastrectomy' above)

•Intragastric balloon (see 'Intragastric balloon' above and "Intragastric balloon therapy for weight loss")

•Adjustable gastric banding – Rarely performed due to the high risk of requiring revision surgery. (See 'Adjustable gastric banding' above and 'AGB revisions' above.)

●Other FDA-approved devices – The following weight loss devices are approved by the US Food and Drug Administration (FDA) but not yet endorsed by the ASMBS. All of them are deployed endoscopically.

•Endoscopic gastric remodeling (see 'Endoscopic gastric remodeling' above)

•Transpyloric shuttle (see 'Transpyloric shuttle' above)

●Revisional procedures – While most people who experience weight recidivism do so because of a failure to adhere to a healthy lifestyle, technical problems such as gastric pouch enlargement can be corrected endoscopically (eg, with transoral outlet reduction [TORe]) or surgically. (See 'Revisional procedures' above.)

●Comprehensive obesity management – In deciding which MBS procedure to offer, surgeons must consider the patient's desire as well as their physiology, their current body mass index (BMI), their comorbidities, and what the desired outcome is. (See 'Suggestions for choosing a bariatric procedure for patients' above.)

Providers should emphasize that surgery is one aspect of obesity care and that it should always be used in conjunction with nutritional, lifestyle, and psychiatric care. Medical care should also be used when appropriate. Comprehensive care is underutilized when addressing obesity, and it is needed to effectively treat the obesity epidemic.