Bariatric Interventions

Introduction

Bariatric intervention has evolved rapidly since its introduction in the 1950s. In the United States, the number of bariatric procedures has increased exponentially from the early 1990s until 2008. After a brief decrease, likely caused by the great recession (2007-2009) during which many patients may have deferred or delayed elective procedures, the numbers continued to increase, reaching an all-time peak of 256,000 in 2019 (Figure 10-1). The rate of increase was lower in the period between 2011 and 2019 compared to the pre-recession exponential increase; this may be due to a shift in the general perception of bariatric intervention from being a “cure” to being the first step that requires continuing commitment to major changes in lifestyle in order to maintain weight loss. Because of a lack of referrals and stigma, only a small percentage (~1%) of all eligible people receive bariatric surgery.

The most plausible explanation for the observed historical trends, however, is that bariatric intervention has gone through a period of slow acceptance by the medical and lay community and is now an established option for weight loss in patients who qualify. With the introduction of minimally invasive (laparoscopic) surgery and reversible endoscopic procedures, as well as a continuously improving interventional safety profile, the number of bariatric interventions may continue to increase. The introduction of transient bariatric devices, such as intragastric hydrogels, provides an option for patients unable or unwilling to undergo endoscopic or surgical procedures.

Bariatric Devices and Endoscopic Procedures

In recent decades, a number of devices and endoscopic procedures have been developed. Implantable devices which reduce the need for invasive bariatric surgery are therapeutic alternatives. They include gastric balloons (introduced in 1985), EndoBarrier (2007), endoscopic sleeve gastroplasty (2008) and aspiration therapy (2013), to name just a few approaches. Most recently (2019), an orally-administered hydrogel capsule received Food and Drug Administration (FDA) approval, and may represent an attractive option for patients unable to undergo other bariatric or endoscopic procedures.

Intragastric Balloons

Intragastric balloons (IGBs) are one of the most well-established bariatric procedures. An empty balloon is introduced into the stomach either endoscopically or by swallowing a capsule and then inflated with air or saline to varying volumes. This both reduces the stomach volume and alters stomach motility, resulting in a feeling of satiety which then leads to weight loss. The use of IGBs is indicated for 6 to 12 months, and they have to be removed after that period. Intragastric balloons are approved (in conjunction with diet and exercise) for use in patients with a body mass index (BMI) of 30-40; they thus represent an option for patients whose BMI (30-35) excludes them from bariatric surgery, but not for people with a BMI above 40.

There were initially three FDA-approved IGBs on the market: the ReShape Integrated Dual Balloon System, the Orbera Intragastric Balloon System (Figure 10-2 A), and the Obalon Balloon system (Figure 10-2 B). Reshape and Orbera are saline-filled balloons while Obalon is gas-filled. The Reshape system is now being phased out, leaving the other two FDA-approved systems available.

The estimated weight loss with Orbera is 8.5% at 3 months, 11.8% 6 months and 13.3% at 9 months. The most common complication was early balloon removal, with the top three causes being vomiting, patient request and nausea. Orbera has also been studied as a bridge to bariatric surgery in order to achieve pre-operative weight loss of 10% in patients with class III obesity.

In the SMART trial, the Obalon balloon system demonstrated a total body weight loss (TBWL) of 6.6%, with a weight loss maintenance rate of 88.5% at 48 weeks. Most of the reported adverse events were mild, and serious adverse events were rare. The Obalon Navigation System received FDA approval in December 2018, eliminating the need for radiography to confirm balloon positioning and instead utilizing magnetic resonance to provide a real-time image of the balloon on computer screen; this reduced both procedure costs and radiation exposure.

Another study compared fluid-filled IGBs with the gas-filled IGBs, revealing that gas-filled IGBs had lower meta-analytic rates of nausea (55.10 vs. 72.99%) and vomiting (16.2 vs. 76.95%). Gas-filled balloons may be better tolerated compared with the fluid-filled balloons and have not been associated with pancreatitis.

Weight regain is a concern after the balloon has been removed; therefore, the procedure should be combined with lifestyle changes and possibly pharmacotherapy to help maximize weight loss maintenance success rates.

Endoscopic Sleeve Gastroplasty (ESG)

Endoscopic sleeve gastroplasty is a minimally invasive technique intended to reduce the size of gastric reservoir. It utilizes a full thickness endoscopic suturing device to stitch together the anterior and posterior stomach walls and achieve a tubular structure (Figure 10-3). Successful ESG decreases gastric capacity up to 70%.

The mechanisms of ESG weight loss include delayed gastric emptying, increased early satiation and alternation of the gut and metabolic hormones: ghrelin and insulin levels decrease and insulin secretion patterns improve. The gastric fundus and neuronal innervation are left intact, so stasis and delayed transition of food induce early satiety through the stomach-brain signaling pathway.

ESG showed better results than both high intensity diet and lifestyle therapy (HIDLT) and intragastric balloon insertion in TBWL (ESG vs HIDLT: 20.6% vs 14.3%; ESG vs intragastric balloon: 20.6% vs 13.9%). A number of studies reported a TBWL of 14.5% to 20% with ESG in a timeframe of 6-12 months. ESG is safe in patients with class I-III obesity, although one study reported better %BMI loss in patients with class I obesity (BMI under 35). Available data also show that ESG may be an effective long-term weight loss strategy, with 90% of patients maintaining a TBWL of 5% and 61% a TBWL of 10% 5 years after the procedure. ESG has demonstrated significant improvements in obesity-related comorbidities (decreases in A1C, systolic blood pressure, insulin resistance, triglycerides, ALT) and health-related quality of life.

Compared to laparoscopic sleeve gastrectomy (the most common bariatric surgery), ESG is less effective in terms of %TBWL, but has a better safety profile, shorter procedure time, shorter hospital stay and lower incidence of new-onset GERD. Incidence of severe adverse events is low with ESG (1%) and mild events like nausea, vomiting and abdominal pain typically improve after a few days with postoperative care. Importantly, ESG can be reversed if patients do not respond well, though this is almost vanishingly rare (<0.01%).

Primary Obesity Surgery Endolumenal (POSE)

Primary obesity surgery endolumenal is a minimally invasive procedure that modifies the gastric anatomy using a platform which consists of a flexible tube, control handle for maneuverability, an endoscope, four working channels and specialized instruments for grasping tissue and placing anchors. The platform folds stomach tissue in the fundus and distal body using a suture and the specialized tissue anchors, thus preventing fundal accommodation and inducing antral dysmotility (Figure 10-4). This in turn triggers earlier and prolonged gastric distention, which helps patients feel full sooner and eat less. POSE is intended for patients who have not previously had any other bariatric procedures and may be an effective weight loss option for patients with class I and II obesity. Patients with class III obesity can be considered for this procedure if they agree to comply with postoperative care. The overall goal of POSE is to treat early stages of obesity and associated comorbidities and prevent disease progression.

One study of POSE efficacy demonstrated a 45% reduction in excess weight 1 year after the procedure (excess weight being the difference between the actual weight of the patient and their “ideal” weight - the weight at BMI of 25) and an average TBWL of 15%. Patients reported a 50% reduction in hunger and 60% reduction in stomach capacity after the procedure. Another trial noted that patients who had the best results at 1 year (TBWL ≥15%) were younger and had higher initial BMIs. Variables that affect weight loss include age, weight before surgery, overall condition of patient’s health, commitment to lifestyle changes and follow-up care.

The overall frequency of adverse events with POSE is 1%, with the most common serious adverse events being postoperative bleeding, perforation of the stomach, pneumothorax, and perihepatic/perisplenic abscess. No serious long-term adverse events associated with the anchors have been reported.

POSE provides individuals with an alternative option to achieve long-term weight loss and improved health related quality of life without large expenses, long hospital stays and high safety risks. If optimal weight loss is not achieved, POSE does not preclude other bariatric procedures.

Orally-Administered Gastric Hydrogel

Approved by the FDA in April 2019, Plenity (referred to as Gelesis100 in clinical studies) is a novel alternative to endoscopic and surgical bariatric procedures. Plenity is an oral, nonsystemic, superabsorbent hydrogel capsule composed of encapsulated cellulose and citric acid. The orally administered capsule disintegrates in the stomach, releasing the hydrogel particles, which hydrate up to 100 times their initial weight and mix with ingested food to create a larger volume with higher elasticity and viscosity which helps make patients feel fuller (Figure 10-5). The fiber is not absorbed systemically and once it reaches the colon, the hydrogel is broken down and the water is reabsorbed while the remaining fiber particles are eliminated with feces. Plenity works by promoting the feeling of fullness and satiety. It is indicated for adult patients with overweight or obesity with a BMI of 25 to 40 in conjunction with reduced calorie diet and exercise. It is the only intervention approved for patients with a BMI of 25-27.

The efficacy of Plenity was assessed in a 24-week Gelesis Loss of Weight Trial (GLOW) – a randomized, double-blind, placebo-controlled study in adults with BMI of 27 to 40, with or without T2D. A 24-week extension to the study (GLOW-EX) examined the effectiveness of Plenity in maintaining weight loss achieved after 6 months for an additional 6 months, as well as the safety of long-term exposure to Plenity. The co-primary efficacy end points were percent change in body weight from baseline and percent of patients who lost ≥5% body weight from baseline. Plenity was safe and effective at promoting weight loss in adults with overweight or obesity with or without T2D.

In the GLOW trial, patients self-administered three capsules containing either Plenity 2.25 g or a placebo with 500 mL of water 20 to 30 minutes before lunch and dinner (twice daily). Mean weight loss from the baseline was 6.4% in the treatment group compared with 4.4% in the placebo group (P = 0.0007; Figure 10-6 A). Among the participants, 32 subjects in the treatment group and 36 subject in the placebo group had prediabetes or drug-naïve T2D. In participants with these conditions, the mean weight loss from baseline were 8.1% and 5.6% for the treatment and placebo groups, respectively. Overall, in the Plenity group, 59% of patients achieved a weight loss of ≥5% compared to 42% in the placebo group (P <0.001; Figure 10-6 B), and 27% of Plenity-taking patients achieved a weight loss of ≥10%, compared to 15% in the placebo group (P <0.05; Figure 10-6 B).

In GLOW-EX, continuation of treatment combined with lifestyle modifications was offered to 52 eligible participants who had completed the GLOW study and demonstrated a weight loss of ≥3% from the baseline. Of those, 39 enrolled in GLOW-EX for further 24 weeks of treatment. After 48 weeks, the Plenity treatment group had a mean weight loss of 7.6% compared to 7.1% in the initial 24-week GLOW trial. Patients from the placebo group who were switched to Plenity in GLOW-EX had a mean weight loss of 9.4%, compared to 7.1% in the initial 24-week GLOW trial. These results suggest that Plenity is effective at maintaining weight loss beyond the initial 6 months when combined with diet and exercise.

Plenity was well tolerated in the GLOW study, with a favorable safety profile. The incidence of adverse events was comparable between the Plenity and the placebo groups (~70%). The most common adverse events in both groups were gastrointestinal related, with a lower incidence of infections and infestations and musculoskeletal and connective tissue disorders. Overall, gastrointestinal-related AEs were significantly different between groups (P = 0.0248). However, none of the individual gastrointestinal AEs showed statistical significance. The safety results from GLOW-EX were consistent with those from GLOW. Given the indication of Plenity for diabetic patients, another study was conducted to assess whether single-dose co-administration of Plenity and metformin has any effect on the PK parameters or safety compared to metformin co-administration with food. This trial concluded that the effect of Plenity on the pharmacokinetics of metformin was similar to the effect of food, and that Plenity is safe to co-administer with metformin for patients who have diabetes.

Aspiration Therapy (AT)

Aspiration therapy is an endoscopic procedure available for people with a BMI of 35-55 that uses an FDA-approved device called AspireAssist to drain gastric contents (Figure 10-7). Aspire Assist consists of:

• An endoscopic gastronomy tube (A-tube) with a fenestrated intragastric drainage catheter
• A flange (Skin-Port) connected to the external end of the A-tube and closed unless aspirating, to prevent gastric leakage
• A detachable connector, connected to the skin tube when aspirating, used for drainage of gastric contents
• A two-way syphon allowing gastric draining and infusion of water into the stomach
• A 600 mL reservoir
• A drain tube, allowing the disposal of aspirated gastric content.

Patients undergoing AT aspirate approximately 30% of the ingested calories, 30 minutes after meals. After 5-6 weeks (115 uses), the connector locks and can no longer be used, so patients are required to see a healthcare practitioner who will provide a new connector.

Aspiration therapy is used alongside non-high-intensity lifestyle therapy (LT). Patients should be counseled by a healthcare practitioner about LT when they come to exchange the connector.

The observed TBWL at 1 year is around 17-19%, with 80% of weight loss coming from aspiration of calories and the remaining 20% from reduced food intake. Since food particles have to be 5 mm or smaller to fit through the A-tube, this may result in longer chewing time and reduced calorie consumption. Increased water consumption to allow liquid gastric contents to flow out of the A-tube may also increase satiety. The visibility of the gastric aspirate may play a role as well, as patients report that less healthy food options have an unappealing appearance after aspiration, potentially reducing consumption of such foods.

AT is associated with significant improvements in hypertension, hyperlipidemia, type 2 diabetes (T2D) and non-alcoholic fatty liver disease. This improvement in metabolic functions is likely related to the amount and type of weight loss following AT.

The disadvantages of AT include the visibility of the catheter and the time and effort required to aspirate. The safety profile is acceptable, with a serious adverse event incidence of 4.1%, the most common being buried bumper.

EndoBarrier

EndoBarrier is an implantable duodenal-jejunal bypass sleeve shown to be effective at reducing excess weight and minimizing cardiovascular disease (CVD) risk factors (Figure 10-8). It is a fluoropolymer sleeve that is reversibly fixated to the duodenal bulb and extends 80 cm into the small bowel, terminating in the proximal jejunum. This endoscopically inserted device aids weight loss through induction of malabsorption and activating hormonal triggers. Studies using the EndoBarrier found that patients were able to achieve between 11.9% and 23.6% excess weight loss within 12 weeks. A longer trial found that patients were able to achieve 47% mean excess weight loss in 52-weeks. In addition to weight loss, one study found that this procedure resulted in statistically significant reductions in fasting blood glucose (-30.3 ± 10.2 mg/dL), fasting insulin (-7.3 ± 2.6 μU/mL) and A1C (-2.1 ± 0.3%) compared with baseline. The EndoBarrier may also have a positive impact on CVD risk factors, including a reduction in lipid levels and blood pressure.

vBloc

The vBloc (Maestro Rechargeable System; marketed by ReShape Lifesciences) is a laparoscopically-implantable device which is capable of delivering low-energy electrical pulses to the intra-abdominal vagal trunks (Figure 10-9). The role of the vagus nerve in the regulation of metabolism, appetite/satiety and autonomic control of the upper GI tract provided the rationale for developing a therapy that can intermittently deliver a vagal block and reduce the feeling of hunger. The vBloc is indicated in patients with a BMI of 40 to 45, or a BMI of 35 to 39.9 and at least one obesity-related co-morbid condition and who have not achieved the goal weight loss on at least one supervised weight management program in the past five years.

The efficacy of vBloc was assessed in ReCharge, a multicenter, randomized, double-blind trial that enrolled 239 patients to receive either a vBloc device capable of delivering electric pulses or a sham device that was not; the patients in the pulse-capable group received at least 12 hours of vagal block therapy per day. Patients in the vagal block therapy group demonstrated greater TBWL at 12 months (10% vs 6% with sham; P<0.001) and 18 months (9% vs 4% with sham; P<0.001) following implantation. Twenty-four months after implantation, patients who continued vagal block therapy maintained a similar TBWL (8%). The vBloc demonstrated a favorable safety profile, with 94% of reported AEs being of mild or moderate intensity.

The vBloc device thus represents a reasonable and safe option for patients with class III obesity who are hesitant to undergo procedures which modify GI anatomy. While the vBloc has been FDA approved, it is not currently commercially available.

Transpyloric Shuttle

The TransPyloric Shuttle (TPS; developed by BAROnova) is a device composed of a two silicon-based balloons connected by a catheter (Figure 10-10). The TPS is endoscopically introduced into the stomach where is self-assembles, with the smaller balloon positioned in the duodenum and the larger balloon positioned in the pylorus. Properly positioned, the TPS results in more rapid filling and slower gastric emptying. It is indicated for adult patients who have not achieved the desired weight loss with medical strategies and who have a BMI of 35-40, or 30-34.9 with an associated comorbidity. The TPS can remain in the stomach for up to 12 months. In a randomized controlled trial in 302 patients, the TPS group demonstrated a significantly greater TBWL (9.5%) compared to the control group (2.3%; P<0.0001).

Conclusion

Non-surgical endobariatric interventions, including endoscopic procedures and orally-administered intragastric hydrogels, represent a significant leap in bariatric management. Their favorable safety profile and greater reversibility make them an attractive option to patients who qualify and can help bridge the “treatment gap” for patients who do not qualify for or are not interested in bariatric surgery.

Candidates and Qualifications for Bariatric Surgery

Surgical bariatric procedures currently represent the most successful treatment for obesity, but only 1% of the eligible population opts for surgical treatment. The 2019 joint guidelines by the American Association of Clinical Endocrinologists (AACE), The Obesity Society (TOS), American Society for Metabolic & Bariatric Surgery (ASMBS), Obesity Medicine Association (OMA) and American Society of Anaesthesiologists (ASA) present the following eligibility criteria for bariatric surgery:

• Patients with a BMI ≥40 without co-existing medical problems and for whom bariatric procedures would not be associated with excessive risk

According to the AACE/TOS/ASMBS/OMA/ASA guidelines, bariatric surgery may also be considered in:

• Patients with a BMI of ≥35 and at least one obesity-related comorbidity, including T2D, insulin resistance, prediabetes, metabolic syndrome, poorly-controlled hypertension, nonalcoholic steatohepatitis, obstructive sleep apnea, osteoarthritis of the knee or hip and urinary stress incontinence
• Patients with a BMI of ≥35 and any of the following, though the evidence is less clear: obesity hypoventilation syndrome and Pickwickian syndrome (after a careful evaluation of operative risk), idiopathic intracranial hypertension, GERD, severe venous stasis disease, impaired mobility due to obesity and considerably impaired quality of life
• Patients with a BMI of 30-34.9 and T2D with inadequate glycemic control despite optimal lifestyle and medical therapy

The guidelines also state that the BMI eligibility criteria should be adjusted for ethnicity and that bariatric procedures should be considered when there are significant obesity-related complications that cannot be prevented or treated with the amount of weight loss achieved on lifestyle change and medical therapy only.

The rates of overweight and obesity continue to rise among children and adolescents. Recent data has demonstrated the safety and efficacy of bariatric surgery in adolescent patients; intervening early can reduce the risk of persistent obesity. The 2018 ASMBS guidelines present the following indications and contraindications for bariatric surgery in adolescents:

Indications:

• BMI ≥35 or 120% of the 95th percentile, with clinically significant co-morbid conditions, including obstructive sleep apnea (AHI >5), T2D, IIH, NASH, Blount’s disease, SCFE, GERD, or hypertension
• BMI ≥40 or 140% of the 95th percentile

Contraindications:

• A medically correctable cause of obesity
• An ongoing substance abuse problem (within the preceding year)
• A medical, psychiatric, psychosocial, or cognitive condition that prevents adherence to postoperative dietary and medication regimens
• Current or planned pregnancy within 12 to 18 months of the procedure

The ASMBS guidelines also state that before bariatric surgery is attempted, a multidisciplinary healthcare team must decide whether the patient and his/her family members are both able and motivated to adhere to recommended pre- and postoperative treatments.

Patients considering bariatric surgery need to understand the procedure and its potential benefits and risks and be willing to accept the responsibility of long-term compliance to lifestyle changes and medical follow-up. Answers to the following questions may help patients decide whether weight-loss surgery is right for them.

Is the patient:

• Unlikely to lose weight or keep it off over the long-term using other methods?
• Well informed about the surgery and treatment effects?
• Aware of the risks and benefits of surgery?
• Ready to lose weight and improve his or her health?
• Aware of how life may change after the surgery? (For example, patients need to adjust to side effects, such as the need to chew food well and the loss of ability to eat large meals.)
• Aware of the limits on food choices and occasional failures?
• Committed to lifelong healthy eating and physical activity, medical follow-up and the need to take extra vitamins and minerals?

Bariatric Surgical Procedures

• Currently, the following five bariatric procedures are the most commonly used in the United States:
• Roux-en-Y gastric bypass (RYGB)
• Laparoscopic sleeve gastrectomy (LSG)
• Biliopancreatic diversion with or without duodenal switch (BPD or BPD/DS)
• Single Anastomosis Duodeno-Ileal Switch (SADI-S)
• Adjustable gastric banding (AGB).

LSG is the most commonly performed procedure in the United States as of 2019, accounting for 61.4% of bariatric surgeries performed. It is followed by RYGB (17.0%). LSG has become very popular due to the simplicity of the procedure, the durability of weight loss and the potential that side effects such as vitamin and mineral deficiencies are less common than with RYGB. Initially, these procedures were performed using open surgical techniques; however, there has been an overwhelming trend toward the use of laparoscopic technologies. For example, the proportion of laparoscopic bariatric operations increased from 20.1% in 2003 to 90.2% in 2008.

Although the mechanisms by which bariatric surgery causes weight loss have not been completely elucidated, the three generally accepted weight loss mechanisms are restriction, malabsorption and hormonal changes. The active mechanism depends on the type of intervention; some procedures can have a restrictive effect on the amount of food (thus the total number of calories consumed), while others involve a combination of restriction plus the bypass of portions of the stomach and small intestine, resulting in changes in the gut biome and hormone milieu. These changes alter appetite, satiety and possibly even metabolism, leading to weight loss.

Roux-En-Y Gastric Bypass (RYGB)

RYGB (often simply called “gastric bypass”) is generally considered the gold standard of weight loss surgery and is the second most commonly performed bariatric procedure worldwide as of 2019, having been overtaken by LSG as in the United States. There are two major steps in this procedure (Figure 10-11). In the first step, the top of the stomach is divided from the rest of the stomach to create a small stomach pouch (~30 mL in volume). Next, the proximal portion of the small intestine is divided (30-40 cm from the junction between the duodenum and jejunum), and the distal end is brought up and connected to the newly created small stomach pouch. The procedure is completed by connecting the top portion of the small intestine to the rest of the small intestine (100-150 cm further down) so that the stomach acids and digestive enzymes from the bypassed stomach and first portion of small intestine will eventually mix with the food. The RYGB is generally considered a nonreversible procedure but can reversed in “emergency” situations.

RYGB leads to weight loss through restrictive, malabsorptive and hormonal changes. First, the newly created stomach pouch is considerably smaller and facilitates significantly smaller meals, which translates into fewer calories consumed. Most importantly, the rerouting of the food stream produces changes in gut hormones that promote satiety and suppress hunger. The concept that RYGB is a strictly malabsorptive procedure has been disproven due to the discovery that there are changes in the gut microbiome and hormone milieu that occur after RYGB, including reduced ghrelin levels and increased nutrient-stimulated peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) levels.

The potential advantages and disadvantages of RYGB according to the American Society for Metabolic and Bariatric Surgery are listed in Table 10-1.

Laparoscopic Sleeve Gastrectomy (LSG)

LSG (often simply called the “sleeve”) is a procedure that permanently removes ~80% of the stomach. (Figure 10-12) The remaining stomach is a tubular pouch that resembles a banana. LSG was originally performed as a modification to another bariatric procedure (BPD/DS) and then later as the first part of a two-stage gastric bypass operation on patients with a BMI >55 for whom the risk of performing gastric bypass surgery was deemed too great. The initial weight loss in these patients was so successful that it began to be investigated as a stand-alone procedure.

Since the new stomach pouch holds a considerably smaller volume than the normal stomach, there is a significantly reduced amount of food (and thus calories) that can be consumed. In addition, like RYGB, LSG alters the gut microbiome and the gut hormone milieux. Ghrelin levels are reduced to a greater extent than after RYGB (since the primary location of ghrelin production - the gastric fundus - is removed), while GLP-1 and PYY are increased, though to a smaller degree than following RYGB. These changes result in reduced hunger, increased satiety and improved blood sugar control.

The potential advantages and disadvantages of LSG according to the American Society for Metabolic and Bariatric Surgery are listed in Table 10-2.

Biliopancreatic Diversion With Duodenal Switch (BPD/DS)

BPD/DS is a two-step procedure. First, a smaller, tubular stomach pouch is created by removing a portion of the stomach, very similar to the sleeve gastrectomy (Figure 10-13). Next, a large portion of the small intestine is bypassed. The duodenum is divided just past the outlet of the stomach. A segment of the distal small intestine is then brought up and connected to the outlet of the newly created stomach. Therefore, when the person eats, the food goes through a newly created tubular stomach pouch and empties directly into the last segment of the small intestine. Roughly three fourths of the small intestine is bypassed by the food stream. The bypassed small intestine, which carries the bile and pancreatic enzymes that are necessary for the breakdown and absorption of protein and fat, is reconnected to the last portion of the small intestine so that they can eventually mix with the food stream. Currently, the BPD/DS is not used very frequently in the United States, although there are a few states in which it is currently performed.

Unlike the other procedures, there is a significant amount of small bowel that is bypassed. Additionally, the food does not mix with the bile and pancreatic enzymes until very far down (100 cm from the end of the small intestine). This results in a significant decrease in the absorption of calories and nutrients (particularly protein and fat) as well as nutrients and vitamins dependent on fat for absorption (fat soluble vitamins and nutrients). Lastly, the BPD/DS, similar to the gastric bypass and sleeve gastrectomy, affects gut hormones in a manner that impacts hunger and satiety as well as blood sugar control.

The potential advantages and disadvantages of BPD/DS according to the American Society for Metabolic and Bariatric Surgery are listed in Table 10-3.

Single Anastomosis Duodeno-Ileal Switch (SADI-S)

SADI-S was developed in 2007 as an attempt to simplify the BPD/DS procedure, primarily by reducing the number of anastomoses (surgical connections between elements of the GI tract). SADI-S consists of a sleeve gastrectomy combined with an end-to-side duodeno-ileal diversion which creates a 200-300 cm channel from the pylorus to the cecum (Figure 10-14). Compared to BPD/DS, SADI-S reduces operation time and the overall complication rate. Postoperative complications are rare. In patients with a shorter (200 cm) common limb between the stomach and the large intestine, nutritional issues such as undernutrition and diarrhea may be present; a common limb of 250-300cm is now the standard. Because of a good record of weight loss (TBWL at 1 year ranged from 21.5% to 41.2% in one meta-analysis) and relatively reduced technical complexity, SADI-S is becoming more widely used.

Adjustable Gastric Band (AGB)

AGB (often simply called the “lap band”) is a laparoscopic procedure in which an inflatable band is placed around the upper portion of the stomach, creating a small pouch above the band and the rest of the stomach below the band (Figure 10-15).

The common explanation of how this device works is that with the smaller stomach pouch, eating just a small amount of food will satisfy hunger and promote the feeling of fullness. The size of the stomach opening can be adjusted by filling the band with sterile saline, which is injected through a subcutaneous port. The size of the opening is gradually reduced over time with repeated adjustments or “fill” until a so-called “sweet spot” is achieved where restriction of the size causes decreased food intake but no regurgitation or obstruction.

The notion that the band is a restrictive procedure (works by restricting how much food can be consumed per meal and by restricting the emptying of the food through the band) has been challenged by studies that show the food passes rather quickly through the band, and that absence of hunger or feeling of being satisfied was not related to food remaining in the pouch above the band. What is known is that there is no malabsorption; the food is digested and absorbed as it would be normally. The clinical impact of the band seems to be that it reduces hunger, which helps the patients to decrease the amount of calories that are consumed.

AGB used to be one of the most common bariatric surgeries, but has declined precipitously: in 2011, it accounted for 35.4% of all bariatric procedures, but constituted less than 1% of bariatric surgeries in 2019. The primary reasons for this shift away from AGB is a high complication and removal rate.

The potential advantages and disadvantages of AGB according to the American Society for Metabolic and Bariatric Surgery are listed in Table 10-4.

Clinical Experience

While there are considerable and increasing clinical trial data on the clinical efficacy and safety of bariatric surgery, the quality of the studies varies considerably due to the difficulties implicit in performing high quality, randomized, controlled trials of surgeries. As a result, most of the data come from studies with less rigorous designs. Nevertheless, the efficacy of the various bariatric procedures is supported by systematic reviews and meta-analyses, as well as the results of individual studies.

Systematic Reviews and Meta-analyses

One early analysis of 147 studies concluded that surgery resulted in a weight loss of 20 to 30 kg, which was maintained for up to 10 years and was accompanied by improvements in some comorbid conditions. One large, matched cohort analysis reported greater weight loss with surgery than with medical treatment in individuals with an average BMI ≥40. For BMIs of 35 to 39, data from case series strongly supported superiority of surgery but was not considered to be conclusive.

A subsequent systematic review included three randomized controlled trials (RCTs) and three cohort studies that compared surgery with nonsurgical interventions and 20 RCTs that compared different surgical procedures. Overall, bariatric surgery was a more effective intervention for weight loss than nonsurgical options. RYGB was more effective for weight loss than LSG and AGB. All comparisons of open vs laparoscopic surgeries found similar weight losses in each group. Comorbidities after surgery improved in all groups, but with no significant differences between different surgical interventions.

Another systematic review analyzed the results of 14 trials (one randomized trial) of at least 1 year of follow-up that compared RYGB and AGB. Excess body weight loss at 1 year was consistently greater for RYGB than with AGB (median difference, 26%; P <0.001). Resolution of comorbidities also was greater after RYGB. In the highest-quality study, excess body weight loss was 76% with RYGB vs 48% with AGB. Both operating room time and length of hospitalization were shorter for those undergoing AGB and perioperative complications were more common with RYGB (9% vs 5%). However, long-term reoperation rates were lower after RYGB (16% vs 24%).

In one systematic review and meta-analysis, Chang and associates analyzed data from 37 randomized clinical trials and 127 observational studies published from 2003 to 2012. A total of 161,756 patients with a mean age of 44.5 years and mean BMI of 45.6 were included. As shown in Figure 10-16, RYGB was more effective for weight loss than AGB.

Although data were limited for LSG, it appeared to be more effective for weight loss than AGB and comparable to RYGB.

Individual Studies

O’Brien and colleagues reported the 15-year follow-up data from their prospective longitudinal cohort study of AGB that enrolled 3,227 patients with a mean BMI of 43.8. Seven hundred fourteen patients completed ≥10 years of follow-up. Among patients who were at ≥10 years post procedure, the mean excess weight loss was 47.0%. This weight loss occurred regardless of whether any revisional procedures were needed. These results were compared with a systematic review of the literature that reported weight loss at ≥10 years after other bariatric procedures. In this review, there was ≥50% excess weight loss with all current procedures (Table 10-5).

The weighted mean excess weight loss with AGB was 54.2% and 54.0% with RYGB. Revisional procedures were performed for proximal enlargement (26%), erosion (3.4%) and port and tubing problems (21%). The band was explanted in 5.6%. Although this was a single-center study, the results support the long-term durability of weight loss with bariatric surgery, specifically laparoscopic ABG.

The Longitudinal Assessment of Bariatric Surgery (LABS) Consortium reported the 3-year follow-up results of a multicenter observational cohort study in 2,458 adults who underwent first-time bariatric surgical procedures between 2006 and 2009 and then followed up until September 2012. At baseline, 79% were women, median BMI was 45.9 and median weight was 129 kg. RYGB was the initial procedure in 1,738 participants; AGB was the initial procedure in 610 participants, while 110 underwent other procedures. At baseline, 774 (33%) participants had T2D, 1,252 (63%) had dyslipidemia, and 1,601 (68%) had hypertension. Three years after surgery, median actual weight loss was 41 kg in RYGB recipients, corresponding to a percentage of baseline weight loss of 31.5%. In AGB recipients, actual weight loss was 20 kg corresponding to 15.9% baseline weight loss. The majority of weight loss was evident 1 year after surgery for both procedures. Among participants who had T2D at baseline, 216 (67.5%) RYGB recipients and 28 (28.6%) LAGB recipients experienced partial remission at 3 years. The incidence of T2D was 0.9% after RYGB and 3.2% after LAGB. Dyslipidemia resolved in 237 (61.9%) RYGB recipients and 39 (27.1%) in AGB recipients; remission of hypertension occurred in 269 (38.2%) of RYGB recipients and in 43 (17.4%) of AGB recipients.

In a 7-year follow-up published by the LABS Consortium in 2018, mean weight loss (from baseline weight) was 28.4% in the RYGB group and 14.9% in the AGB group, with a mean regain of 3.9% and 1.4% mean weight regain between years 3 and 7 in the RYGB and AGB groups, respectively. The prevalence of dyslipidemia was lower than at baseline in both groups, while diabetes and hypertension were lower in the RYGB group only. Of the patients with diabetes at baseline, 60.2% in the RYGB group and 20.3% in the AGB group experienced remission 7 years after surgery.

Although many studies of short-term to mid-term outcomes of LAGB have been published, long-term outcomes reports with a follow-up of ≥10 years are still scarce. One study assessed the long-term results of AGB in 60 consecutive patients (44 women, 16 men) who were treated for class III obesity by AGB between 1996 and 1999. The median age of the patients at the time of operation was 45 years and their median preoperative BMI was 45. All patients were instructed to adhere to a strict follow-up program. Complete data on all 60 patients could be assessed; thus, the overall rate of follow-up was 100%. After a median follow-up of 14.1 years, the mean BMI decreased from 45 to 36, with a mean 49% excess weight loss (EWL). At 15 years of follow-up, 48% of bands had been removed. In those patients with the band still in place at 14 years, 40% had >50% EWL while 20% had <25% EWL.

The efficacy and complications of LSG were assessed in a prospective cohort of 68 patients who underwent LSG either as primary bariatric procedure (n = 41) or as a redo operation after failed AGB (n = 27) between August 2004 and December 2007. At the time of LSG, the mean BMI was 43, the mean age was 43.1 years and 78% were female. The follow-up rate was 100% at 1 year postoperatively, 97% after 2 years and 91% after 5 years; the mean follow-up time was 5.9 years. The average EWL was 61.5% after 1 year, 61.1% after 2 years and 57.4% after 5 years. Comorbidities improved considerably. For example, remission of T2D was achieved in 85% of cases. Complications included: one leak (1.5%), two incisional hernias (2.9%) and new-onset gastroesophageal reflux in 11 patients (16.2%). Reoperation due to insufficient weight loss was necessary in eight patients (11.8%).

A retrospective cohort analysis compared clinical outcomes in 190 consecutive patients who underwent primary BPD/DS between 2005 and 2010, of whom 178 (93.7%) were available for follow-up. These patients were matched with 139 patients who underwent primary RYGB in the same medical center during the same period. While percentage changes from baseline in each group were significant, there was no significant difference in percent total weight loss between groups. T2D, hypertension and hyperlipidemia all improved significantly within each group, although the improvements were significantly higher in the BPD/DS group. Loose stools and bloating symptoms were more frequently reported among BPD/DS patients. With the exception of increased emergency department visits among BPD/DS patients (P <0.01), overall complication rates were not significantly different between BPD/DS and RYGB. There was no difference in mortality rates between the groups.

In an Israeli trial of 8,385 patients with obesity who underwent bariatric surgery (AGB, RYGB, or LSG) and 25,155 matched controls who received usual care (non-surgical, including dietary and behavioral counseling), the all-cause mortality over a course of ~4.5 years was lower in the surgery group (1.3% overall; 1.7% for AGB, 1.3% for RYGB, 0.8% for LSG) than in the non-surgery group (2.3%; adjusted hazard ratio = 2.02). These results underscore the benefit of bariatric surgery to overall health beyond weight loss.

The Swedish Obese Subjects Study

The Swedish Obese Subjects (SOS) study is an ongoing, nonrandomized, prospective, controlled study conducted at 25 public surgical departments and 480 primary health care centers in Sweden that included 2010 participants with obesity who underwent bariatric surgery and 2037 contemporaneously matched participants with obesity who received usual care. Participants were followed up for a median of 14.7 years. The objectives of the SOS study were to determine the long-term effects of weight-loss surgery on “hard” clinical endpoints, including overall mortality, CV events, incidence of diabetes and stroke. Of the patients who had surgery, 13% underwent a bypass procedure, 19% underwent a banding procedure, while 68% had vertical banded gastroplasty.

In the surgery group, the mean changes in body weight after 2, 10, 15 and 20 years were -23%, -17%, -16% and -18% while the mean changes in the usual care group were 0%, 1%, -1% and -1%. Compared with usual care, bariatric surgery was associated with a long-term reduction in overall mortality (adjusted HR = 0.71, P = 0.01). Bariatric surgery also was associated with a reduced number of CV deaths (28 events among 2010 patients in the surgery group vs 49 events among 2037 patients in the control group (HR = 0.47; P = 0.002). The number of total first time (fatal or nonfatal) CV events (myocardial infarction or stroke, whichever came first) was also lower in the surgery group (199 events among 2010 patients) than in the control group (234 events among 2037 patients; HR = 0.67; P <0.001). Perhaps the most striking finding was that during the follow-up period, the incidence of T2D was substantially lower than in the usual care group (6.8 cases per 1000 person-years vs 28.4 cases per 1000 person-years, respectively (HR = 0.17; P = 0.54).

Safety

Operative (30-day) mortality for bariatric surgery has been reported to range from 0.1% to 2%. These rates depend on several factors: complexity of the operation, patient comorbidities and experience of the surgeon and the center. AGB typically has the lowest mortality rate of 0.1%, whereas the rate with RYGB or VSB is ~0.5%. Higher mortality rates have been correlated with visceral obesity, sex, BMI ≥50, diabetes mellitus, sleep apnea and older age.

In the meta-analysis of 147 studies discussed above, the overall rate of AEs in bariatric surgery was 20%. Laparoscopic approaches resulted in fewer wound complications than open procedures.

Early general complications include thromboembolism (1%), pulmonary or respiratory insufficiency (<%), hemorrhage (1%), peritonitis (1%) and wound infection (2%). The increased use of laparoscopy has been instrumental in decreasing these rates. GI obstructions are of most concern among long-term complications. The cause of the obstruction typically depends on the type of bariatric procedure. For example, gastric obstruction associated with AGB may be due to food entrapment at the narrowed banded area, from overinflation of the band, or from band “slippage,” which causes pouching over the band. Symptoms can be resolved by loosening the band but in certain circumstances, surgical repositioning of the band is necessary. Gastric obstruction associated with RYGB or LSG may be caused by stenosis of the gastric outlet secondary to scar tissue and may be treated with endoscopic dilation. Intestinal obstruction can occur after gastric bypass or other malabsorptive procedures and typically requires urgent surgical intervention.

Topart and colleagues retrospectively reviewed their 2-year, single institution bariatric surgery experience to compare the 30-day morbidity and 90-day mortality rates with LSG (n = 88), RYGB (n = 360), and BPD-DS (n = 59). Thirty-day morbidities were significantly more frequent with LSG and BPD-DS than with RYGB. The global complication rate was significantly higher after BPD-DS (P = 0.0017) compared with RYGB, however, there was no difference between RYGB and LSG. Compared with RYGB, bleeding was more frequent, after comparison with BPD-DS and LSG.

In the meta-analysis by Chang and colleagues (discussed above), the overall complication rate was 17% in RCTs (Table 10-6). This pattern persisted across all of the surgical procedures. In RCTs, complications rates were relatively low for LSG (13%) and AGB (13%) compared with VGB (21%). Reoperation rates were not as high as complication rates. In RCTs, RYGB appeared to have the lowest reoperation rate (3%) followed by LSG (9%).

Surgery as Diabetes Treatment

Weight loss has long been regarded as the first approach to prevent T2D in high-risk subjects and to manage the metabolic derangements of established T2D. The attractiveness of weight control as a therapeutic intervention and the limited efficacy of producing medically induced weight loss has led to increased interest in the effect of surgically produced weight loss to correct the metabolic abnormalities in patients with established T2D and to prevent or remit T2D in high-risk individuals.

Although the results of clinical trials so far have been promising, there still is a lack of consensus regarding the minimum BMI requirement and uncertainties regarding the comparative effectiveness of different bariatric procedures, especially in the long term. For example, in one literature review, bariatric surgery in T2D patients with a BMI of ≥35 resulted in a 56% EWL and remission of T2D in 57% to 95% of patients, depending on the type of surgery and the definition of diabetes resolution. Four other reviews reported similar benefits of surgery in adults with T2D or other metabolic conditions and a BMI of 30.0 to 34.9. In many trials, there also were significant benefits in other comorbidities.

Several trials also reported beneficial effects of bariatric surgery in patients with T2D. However, it is difficult to compare the studies due to the difference in type of procedures used as well as different definitions of remission of diabetes. A randomized, non-blinded, single-center trial evaluated the efficacy of intensive medical therapy alone vs medical therapy plus RYGB or LSG in 150 patients with obesity and uncontrolled T2D. The mean age of the patients was 49 years, and 66% were women. The average baseline A1C was 9.2%. The primary end point was the proportion of patients with an A1C level of 6% or less 12 months after treatment. Of the 150 patients, 93% completed 12 months of follow-up. The proportion of patients with the primary end point was 12% in the medical-therapy group vs 42% in the RYGB group (P = 0.002) and 37% in the LSG group (P = 0.008).

Glycemic control improved in all three groups, with a mean A1C level of 7.5% in the medical-therapy group, 6.4% in the RYGB group (P <0.001) and 6.6% in the LSG group (P = 0.003). The index for homeostasis model assessment of insulin resistance (HOMA-IR) improved significantly after both bariatric procedures. Weight loss was greater in the RYGB and LSG groups (-29.4 kg and -25.1 kg, respectively; P <0.001 for both comparisons) than in the medical-therapy group (-5.4 kg; P <0.001 for both comparisons). In addition, use of drugs to lower glucose, lipid and BP levels decreased significantly after both surgical procedures but increased in patients receiving medical therapy only. Four patients underwent reoperation. There were no deaths or life-threatening complications.

Another single-center, non-blinded, randomized, controlled trial in 60 adult patients compared the effects of bariatric surgery vs conventional medical therapy for T2D in patients with BMI ≥35 and a history of T2D for at least 5 years and a baseline A1C level of ≥7.0%. Patients were randomly assigned to receive conventional medical therapy or undergo either RYGB or BPD. The primary end point was the rate of T2D remission at 2 years (defined as a fasting glucose level of <100 mg per deciliter [5.6 mmol/l per liter] and an A1C level of <6.5% in the absence of pharmacologic therapy). At 2 years, no patients in the medical-therapy group experienced T2D remission compared with 75% of those in the RYGB group and 95% of those in the BPD group (P <0.001 for both comparisons).

Age, sex, baseline BMI, duration of T2D and weight changes were not significant predictors of T2D remission at 2 years or of improvement in glycemia at 1 and 3 months. At 2 years, the average baseline A1C level (8.65%) had decreased in all groups, but patients in the two surgical groups had the greatest degree of improvement in average A1C levels, 7.69% in the medical-therapy group, 6.35% in the RYGB group and 4.95% in the BPD group.

An analysis of clinical outcomes in 217 patients with T2D who underwent bariatric surgery (RYGB [n = 162]; AGB [n = 32]; LSG [n = 23]) between 2004 and 2007 and had at least 5-year follow-up assessed the effects of bariatric surgery on long-term T2D remission rates. Overall, RYGB resulted in the greatest short-term and long-term reductions in total and EWL weight loss (Table 10-7). Complete remission was defined as A1C <6% and FBG <100 mg/dL off diabetic medications. At a median follow-up of 6 years after surgery a mean EWL of 55% was associated with mean reductions in A1C from 7.5% to 6.5% (P = 0.001) and FBG from 155.9 to 114.8 (P <0.001). Long-term complete and partial remission rates were 24% and 26%, respectively, whereas 34% of patients improved (>1% decrease in A1C without remission) from baseline and 16% remained unchanged. Shorter duration of T2D (P <0.001) and higher long-term EWL (P = 0.006) predicted long-term remission. Recurrence of T2D after initial remission occurred in 19% of patients and was associated with longer T2D duration (P = 0.03), less EWL (P = 0.02) and weight regain (P = 0.015).

On the basis of evidence available, the IDF issued a position statement stating that bariatric surgery can be considered an appropriate treatment for individuals with a BMI of ≥35 or greater and T2D who have not achieved recommended treatment targets with medical therapies, especially in the presence of other major comorbidities.

Bariatric Surgery and Obstructive Sleep Apnea

Obesity, older age, male sex and heredity are well-established risk factors for OSA, with obesity being the single most important modifiable risk factor. If untreated, OSA is associated with increased risk of diabetes, CV disease, driving accidents and all-cause mortality. However, few studies have compared the effect of surgical and conservative weight loss strategies on OSA in patients with obesity.

A one-year study in a total of 133 patients with class III obesity (70% females) were treated with either a 1-year ILI program (n = 59) or bariatric surgery (RYGB) (n = 74) and underwent repeated sleep recordings with a portable somnograph. At baseline, participants had a mean age of 44.7 years, a mean BMI of 45.1 and an AHI of 17.1 events/hour. Eighty-four patients (63%) had a diagnosis of OSA. The average weight loss was 8% in the ILI-group and 30% in the RYGB-group (P <0.001). The mean AHI decreased in both treatment groups, although significantly more in the RYGB group (group difference 7.2; P = 0.017) and 66% of RYGB-treated patients experienced remission of OSA compared with 40% of the ILI-patients (P = 0.028).

At follow-up, after adjusting for age, gender and baseline AHI, the RYGB-patients had significantly lower adjusted odds for OSA than the ILI-patients (OR 0.33; P = 0.0150). However, after further adjustment for BMI change, the treatment group difference was no longer statistically significant (OR 1.31; P = 0.709). The authors concluded this study demonstrates that RYGB was more effective than ILI at reducing the prevalence and severity of OSA. However, further analysis also suggests that weight loss, rather than the surgical procedure per se, explains the beneficial effects bariatric surgery in individuals with obesity.

Many studies have reported significant improvement of OSA in patients with obesity after bariatric surgery. It also has been noted that weight loss following surgery often is rapid in the first few months but often can take at least 1 year to reach the maximum effect. In order to assess the time course of the benefits of bariatric surgery, one study compared the effects of bariatric surgery on its effects at two postoperative intervals.

Patients who had been diagnosed with OSA preoperatively were invited to undergo PSG at least 6 months postoperatively and again at least 12 months postoperatively if OSA persisted. At a mean of 7.7 months after surgery, 110 patients completed a first postoperative PSG. At that time, the mean AHI had decreased significantly from 39.5/hr to 15.6/hr. In 26% of patients, the AHI was reduced to <5/hr. Fifty patients underwent a first PSG at a mean of 7.1 months and a second PSG at a mean 16.9 months after surgery. The mean AHI decreased significantly from a baseline of 49.1/hr to 2.7/hr and 17.4/h following bariatric surgery. Thus, while the beneficial effects of bariatric surgery occur early in the postoperative period, they continue at a slower rate. Therefore, the authors suggest that follow-up PSG after surgery should be considered to check for residual disease and possible retitration of continuous positive airway pressure.

Bariatric Surgery in Adolescents

The most recent (2017-2018) national data on obesity prevalence indicate that about 19.3% US children and adolescents had obesity, presenting a major current and future health problem as many of these individuals age and become adults with obesity and longstanding comorbidities. Weight-loss surgery is used to treat selected adolescents with obesity, although with very limited data regarding the safety of currently used, minimally invasive procedures.

An ongoing prospective, multisite observational study (Teen-LABS) assessed the preoperative clinical characteristics and perioperative safety outcomes in 242 adolescent patients with class III obesity aged 19 years or younger who underwent weight-loss surgery from February 28, 2007 through December 30, 2011. The mean age of participants was 17.1 years and the median BMI was 50.5. At baseline, 51% demonstrated four or more major comorbid conditions. The procedures included RYGP, LSG and AGB in 66%, 28% and 6% of patients, respectively. There were no deaths during the initial hospitalization or within 30 days of operation.

Major complications (e.g., reoperation) occurred in 19 patients (8%). Minor complications (e.g., readmission for dehydration) were noted in 36 patients (15%). All reoperations and 85% of readmissions were related the surgery itself. At this time, this study reported a favorable short-term complication profile, supporting the early postoperative safety of weight-loss surgery in selected adolescents with obesity. At the 3-year follow-up, mean weight was reduced by 27% in the patients who underwent gastric bypass and by 26% in those who underwent a sleeve gastrectomy. At this time point, high percentages of participants achieved a remission in T2D (95%), abnormal kidney function (86%), prediabetes (76%), elevated blood pressure (74%) and dyslipidemia (66%). In a 5-year follow-up report, mean weight was 26% lower compared to baseline and remission rates of T2D and hypertension remained high (86% and 68%, respectively).

A recent analysis of Teen-LABS data has revealed few differences in the post-surgical outcomes of younger (13-15 years of age) and older (16-19 years of age) adolescents, suggesting that younger age should not by itself be a criterion for not considering bariatric surgery. This cohort is still being followed in order to provide longer-term data.

Postsurgical Care

It is important for patients to have long-term follow-up with their bariatric surgeon; after the first year the expectation is that patients will see their surgeon annually.

Follow-up of the patients with obesity who have had bariatric surgery can be divided into three categories: the issues of surgical complications and weight loss during the first year, the nutritional and metabolic concerns that typically arise after the first postoperative year, and the problem of weight maintenance over the longer term.

Female patients should be advised that pregnancy is contraindicated for at least 18 months after surgery because of the rapid weight loss and nutritional requirements. In addition, all patients should be encouraged to stop both smoking and the use of alcohol.

Short-term complications of bariatric surgery include vomiting, wound infections, stomal stenosis (i.e., narrowing of the gastrojejunostomy), marginal ulceration and constipation.

Common long-term complications of bariatric surgery include cholelithiasis, dumping syndrome, persistent vomiting and nutritional deficiencies.

Because bariatric surgery affects a number of metabolic and neuro-hormonal processes, it is the most successful intervention for lowering the body weight “set point”. However, a variable proportion of patients still experience some degree of weight regain - depending on the study population and surgery type, observed weight regain has ranged from <10% to >90%. Overall, it appears that a substantial minority (25-35%) of patients experience significant (at least 15%) weight regain following surgery. Preoperative predictors of weight regain include a higher BMI and psychiatric comorbidities. Postoperatively, the most important factors are diet/exercise noncompliance, hormonal or metabolic imbalance and psychiatric comorbidities. Behavioral support (dietary counseling/intervention, cognitive behavioral therapy) has been shown to be efficacious in counteracting weight regain. Pharmacological support may also be useful - significant postoperative weight-loss effects have been reported for orlistat, topiramate, phentermine/topiramate and liraglutide.

Table 10-8 provides a list and suggested schedule of laboratory tests useful for long-term follow-up of patients who have had bariatric surgery.

Summary

Bariatric surgery has evolved since the 1950s with the emergence of the jejunoileal bypass and now includes the RYGB, LSG, BPD/DS, SADI-S and AGB. These procedures have been shown to produce significant and durable weight loss as well as reduction or resolution of the serious comorbidities associated with obesity including mortality. Comparative studies on surgical procedures vs control groups have suffered from the inability to conduct randomized controlled clinical trials; however, long-term studies have been published which clearly show benefit. The introduction of endoscopic techniques and orally-administered devices in recent decades has revolutionized the field; while it is too early to say how such modalities will develop in the future, they are likely to complement traditional surgical interventions and pharmacotherapy in the management of obesity and its comorbidities. The exact mechanism of action of the durable weight loss in especially the combination procedures are still being researched, but a combination of restriction and change in gut hormone milieu seems to be partly if not completely responsible for the reduction in appetite and increase in satiety, and hence, weight loss. Despite the known benefits, only a small number of eligible patients undergo bariatric surgery every year. Physicians should consider discussing bariatric surgery and endobariatric procedures with patients who qualify.