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Obesity Primer for the Practicing Gastroenterologist

Jirapinyo, Pichamol MD, MPH1,2; Thompson, Christopher C. MD, MSc1,2

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The American Journal of Gastroenterology: May 2021 - Volume 116 - Issue 5 - p 918-934
doi: 10.14309/ajg.0000000000001200
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Obesity has become pandemic. It is estimated that more than 650 million adults (13% worldwide) suffer from obesity (1). In the United States, the prevalence is even higher with 42.4% of adults meeting criteria for obesity (2). As of 2013, the American Medical Association officially recognized obesity as a chronic disease (3).

There are several ways to define and categorize obesity. Per the Obesity Medicine Association, obesity is “a chronic, relapsing, multifactorial, and neurobehavioral disease, wherein an increase in body fat promotes adipose tissue dysfunction and abnormal fat mass physical forces, resulting in adverse metabolic, biomechanical, and psychosocial health consequences (4).” Traditionally, obesity has also been defined as a body mass index (BMI) of at least 30 kg/m2. It is further categorized into class I obesity (BMI 30–34.9 kg/m2), class II obesity (BMI 35–39.9 kg/m2), and class III obesity (BMI ≥40 kg/m2) (5). The use of BMI, however, is limited in certain populations, such as the elderly, muscular, and sarcopenic, because it does not distinguish between lean muscle and body fat or its location (6). Alternatively, waist circumference (WC) may be used. Specifically, for patients with a BMI of 25–34.9 kg/m2, WC of ≥40 inches (>102 cm) in men and ≥35 inches (>88 cm) in women suggest central obesity, which is associated with increased cardiometabolic risk (7–9). Finally, obesity may also be defined as body fat percentage of ≥ 25% in men and 35% in women with the healthy body fat ranging from 8% to 19% in men and 21%–35% in women (depending on age) (4,10,11). Nevertheless, accurate body composition testing can be expensive with limited availability. Furthermore, it is important to note that these cutoffs vary based on ethnicity, such as a BMI of ≥25 and ≥27 kg/m2 being used to define obesity in Asian and Middle East populations, respectively, because of their higher body fat at a lower BMI and earlier appearance of comorbidities (12,13).

This review is intended to serve as a clinical guide for the general gastroenterologist on the assessment and management of obesity. Tables containing high-yield information are also provided for quick reference.


Obesity is associated with several gastrointestinal (GI) conditions including various esophageal, gastric, small intestinal, colonic, hepatobiliary, and pancreatic diseases (14–17). Specifically, obesity may result in a higher incidence, earlier presentation, and more severe clinical manifestations of these diseases. For example, obesity increases the risk of gastroesophageal reflux disease, esophagitis, and esophageal adenocarcinoma by 2-, 1.8-, and 2.8-fold, respectively (18). Similarly, the incidence of nonalcoholic fatty liver disease is approximately 90% in patients with obesity, compared with 25% in the general population (19), and obesity has been shown to hasten the progression from compensated to decompensated cirrhosis (20). However, weight loss of at least 7%–10% total weight loss (TWL) has been shown to reverse histologic features of fatty liver (21). A more extensive list of obesity-related GI conditions is summarized in Table 1 and can be more deeply explored in the work of Camilleri et al. (14). Given these associations, gastroenterologists should have an increased suspicion and low threshold to look for these illnesses in this patient population. In addition, early diagnosis of obesity and timely evaluation and management may help reduce the prevalence and severity of such disorders.

Table 1.
Table 1.:
Gastrointestinal conditions associated with obesity


The obesity evaluation consists of several elements including medical, lifestyle, psychological, and endoscopic assessments.

Initial evaluation

During the initial encounter, physicians should assess patients' readiness to change their health behavior using the “Stages of Change” model (22,23). Specifically, the model consists of 5 stages: (i) precontemplation: the individual is unaware of the consequences of their behavior and resistant to change, (ii) contemplation: the individual is aware of the consequences and open to change, (iii) preparation: the individual shows anticipation and willingness to change within the next 6 months, (iv) action: the individual is in the process of changing their behavior, and (v) maintenance: the individual has sustained the new behavior for more than 6 months. For patients in the precontemplation stage, the goal is to help move them to the contemplation stage before referral to bariatric specialists. Motivational interviewing techniques, such as the 5 A's (Ask, Advise, Assess, Assist, and Arrange) and OARS (Open-ended questions, Affirmations, Reflections, and Summaries), can help with this process to elicit and strengthen patient's motivation along this spectrum (24,25).

Medical evaluation

A weight-focused history, physical examination, and laboratory evaluation should be obtained. Weights at specific time points, including around the major life events, and the effectiveness of previous weight loss attempts should be reviewed. Certain medications can cause weight gain and should be downtitrated or substituted with weight neutral drugs (Table 2) (26,27). On physical examination, BMI, WC, waist-hip ratio, and percent body fat should be measured. Signs of obesity-associated medical conditions including hyperpigmented skin around the neck or axilla (acanthosis nigricans associated with insulin resistance), hirsutism (polycystic ovarian syndrome), large neck circumference (>17 inches for men or >16 inches for women suggesting increased risk of sleep apnea), and thin, atrophic skin (Cushing disease) should be looked for (28). Baseline laboratory should include electrolytes, renal function, fasting glucose, hemoglobin A1c (HbA1c), liver enzymes, complete blood count, lipid panel, thyroid-stimulating hormone, vitamin D, and urine albumin.

Table 2.
Table 2.:
Medications associated with weight gain, weight neutrality, and weight loss

Lifestyle evaluation

Dietary and eating habits should be reviewed using a 24-hour diet recall, food frequency questionnaire, or food log. Dietary habits including eating patterns (skipping breakfast, eating one large meal per day, emotional eating, and grazing), frequency of eating out, and grocery shopping details should be evaluated. Furthermore, onset of satiation (the point at which one becomes full ending one's desire to eat during a single meal) and period of satiety (the state of being full and satisfied which regulates the time elapsed between 2 meals) should be assessed.

Physical lifestyle should be assessed. It is important to understand whether patients have an active or sedentary lifestyle and details regarding exercise (types, duration, and frequency). Total energy expenditure (TEE) is the amount of calories burned per day. It is composed of resting energy expenditure (REE), thermic effect of meals (TEM), and energy expenditure from physical activity (EEPA), which is further broken down into exercise and nonexercise activity thermogenesis (NEAT).

REE is the energy cost of physiological functions at rest, such as respiration, cardiac output, and body temperature regulation. TEM is the energy required for digestion, absorption, and disposal of ingested nutrients. Its magnitude depends on macronutrient composition with proteins requiring the most energy (20%–35% of energy consumed), followed by carbohydrates (5%–15%) and fats (5%–15%) (29,30). EEPA consists of exercise and NEAT, which is the energy expended for physical activity that is not sleeping, eating, or exercise. As shown in the equation, changing one's lifestyle directly affects EEPA, resulting in changes in TEE and daily net calories.

Psychological evaluation

Psychiatric history including anxiety, depression, and post-traumatic stress disorder should be assessed because this may translate into eating disorders. It is important to assess whether patients suffer from bulimia nervosa (recurrent episodes of binge eating + inappropriate compensatory behavior to prevent weight gain), binge eating disorder (recurrent episodes of binge eating without compensatory behavior), purging disorder (recurrent purging behavior without binge eating), and night eating syndrome (recurrent episodes of night eating) because these require referral to a mental health specialist (31). Physicians may consider using the Eating Disorder Examination Questionnaire for screening purposes (Table 3) (32,33).

Table 3.
Table 3.:
Eating Disorder Examination Questionnaire (EDE-Q) (32,33))
Table 3-A.
Table 3-A.:
Eating Disorder Examination Questionnaire (EDE-Q) (32,33))

Endoscopic evaluation

Endoscopy may be required as part of the initial evaluation for a subgroup of patients with obesity. In addition, for those who are undergoing bariatric surgery, the International Federation for the Surgery of Obesity and Metabolic Disorders recommends that a preoperative esophagogastroduodenoscopy should be considered for all patients with and without GI symptoms (34). During this procedure, one should note the presence of a hiatal hernia (Hill Grade I–IV), esophagitis, Barrett's esophagus, gastric polyps, gastritis, Helicobacter pylori infection, and malignancy. According the systematic review and meta-analysis conducted by the International Federation for the Surgery of Obesity and Metabolic Disorders task force (63 studies/22495 patients), abnormal esophagogastroduodenoscopy findings are likely to be found in at least 55.5% of patients before bariatric surgery (25.3% for a subgroup of asymptomatic patients) with 16.5% having findings that led to modification or delay of the planned procedure and 0.2% having surgery cancelled (34).

Gastroenterologists should also be familiar with postbariatric surgical anatomy including normal and abnormal endoscopic findings. For Roux-en-Y gastric bypass (RYGB), the pouch and gastrojejunal anastomotic sizes should be assessed. The presence, location, and size of marginal ulceration and gastrogastric fistula should be documented. For sleeve gastrectomy (SG), the sleeve dimension/configuration and the presence of sleeve stenosis and/or angulation should be assessed. Furthermore, given the prevalence of de novo reflux (23%) after SG, gastroenterologists should be vigilant in assessing for the presence of esophagitis (found in up to 53%) and Barrett's esophagus (found in 11.6%) in this patient population (34,35). For laparoscopic adjustable gastric band, retroflexion to evaluate for band erosion should be performed.

Other evaluation

After the initial evaluation, additional studies, such as direct/indirect calorimetry, Homeostatic Model Assessment of Insulin Resistance, liver ultrasound with elastography, and magnetic resonance elastography, may be obtained on a case-by-case basis. Furthermore, referral to appropriate specialists for signs or symptoms of non-GI obesity-related comorbidities should be considered.


The spectrum of obesity treatment options includes lifestyle modification, pharmacotherapy, endoscopy, and surgery.

Lifestyle modification

Lifestyle modification (LM) is considered first-line therapy for the treatment of obesity. It includes 3 primary components—diet, exercise, and behavioral therapy.

To achieve weight loss, an energy deficit is required. This can be accomplished by restricting caloric intake or limiting certain food types. To reduce caloric intake, women should target 1,200–1,500 kcal/d, whereas men target 1,500–1,800 kcal/d (8). Alternatively, an individual's energy requirement may be estimated using calorimetry or available equations, and an energy deficit of 500–750 kcal/d or a 30% energy deficit can be prescribed. Alternatively, instead of a formal energy deficit target, lower calorie intake may be achieved by restriction or elimination of particular food groups, such as carbohydrates. According to the US Dietary Guidelines, the recommended macronutrient proportions consist of carbohydrate (45%–65%), protein (10%–35%), and fat (20%–35%) (36). Adjusting these proportions may facilitate weight loss in some individuals by simplifying dietary goals. Although there are no universally accepted definitions, examples of macronutrient-focused diet plans include high protein (≥20%–30% protein), low carbohydrate (<20% carbohydrate), and low fat (<15%–20% fat) diets (37–40). There are several randomized, controlled trials comparing diets with various macronutrient compositions. The largest study conducted by Sacks et al. randomized 811 overweight adults to 1 of 4 diets—low fat/average protein (highest carbohydrate: 65% of calories), low fat/high protein, high fat/average protein, and high fat/high protein (lowest carbohydrate: 35% of calories). No significant differences in weight loss were observed among the 4 groups at 2 years (41). Other trials also demonstrated similar results with meta-analyses showing that adherence is the strongest predictor for weight loss (42). Macronutrient content may affect patient preferences but is only one of many factors influencing adherence. Given the relatively equivalent efficacy of different dietary approaches, a diet plan may be chosen based on metabolic risk factors and patient preferences. Specifically, low fat diets induce greater reduction in low-density lipoprotein, whereas low carbohydrate diets are associated with greater improvement in triglycerides, high-density lipoprotein, and HbA1c (41,43–46). Table 4 summarizes the more commonly prescribed diet plans.

Table 4.
Table 4.:
Dietary interventions for weight loss
Table 4-A.
Table 4-A.:
Dietary interventions for weight loss

Physical activity is an essential component of a weight loss program. Specifically, at least 150 minutes of aerobic activity per week is recommended (at least 30 minutes per day, most days of the week) (8,47), with at least 2 resistance training days per week (minimum of 1 set of 8–12 repetitions for a total of 8–10 exercises per week) (48). Resistance training is important because it helps improve muscle strength and endurance, modify coronary risk factors, and preserve fat-free mass during weight loss to enhance metabolic rate (49,50). During the weight maintenance phase, higher levels of physical activity of 200–300 minutes per week are recommended (51).

Behavioral therapy targets maladaptive eating behaviors, activity, and thinking habits that contribute to obesity. It includes several components. Self-monitoring is perhaps the most important component of behavioral therapy. Patients are advised to record the type, amount, and total calories of their food consumption, and physical activity and body weight. Studies show that individuals that routinely record their food intake lose more weight than those who do not (52). Other components of behavioral therapy include (i) stimulus control (such as storing food out of sight, limiting eating places to the kitchen and dining table, and refraining from eating while engaging in other activities), (ii) problem solving (such as planning meals ahead of time while traveling), (iii) cognitive restructuring (such as recognizing a setback as a temporary lapse and continuing to move forward instead of giving up), and (iv) relapse prevention focusing on high-risk situations (such as vacations, illness, or periods of high stress). Traditionally, behavioral therapy is offered in group sessions of 10–20 individuals by registered dietitians, psychologists, exercise specialists, or other health professionals, with each session lasting 60–90 minutes. It is often held weekly during the active weight-loss phase (6 months) and may taper to biweekly during the weight-maintenance phase (53).

In clinical practice, LM is usually prescribed comprehensively to modify both eating and activity habits. To date, there are 2 landmark studies evaluating the efficacy of LM: the Diabetes Prevention Program and Look AHEAD studies (54). The Diabetes Prevention Program study compared LM (16 sessions during the first 6 months, followed by monthly contacts) with metformin with placebo at delaying or preventing development of type 2 diabetes (T2DM) in 3,200 patients with impaired glucose tolerance. At 1 year, LM patients lost 7 kg compared with 0.1 kg for placebo. The risk of developing T2DM was reduced by 58% in the LM group compared with placebo and 31% compared with metformin. At 10 years, participants regained almost all of their lost weight (with no differences in weight loss among groups). Nevertheless, the incidence of T2DM remained the lowest in the LM group (55). In comparison, the Look AHEAD study evaluated the effect of intensive lifestyle intervention (ILI) (24 sessions during the first 6 months, followed by 18 sessions in months 7–12) vs usual care (diabetes support and education) in 5,100 overweight participants with T2DM. At 1 and 4 years, patients in the ILI and diabetes support and education experienced 8.6% vs 0.7% TWL and 4.7% vs 1.1% TWL, respectively. The ILI group also experienced significantly greater improvement in HbA1c and several measures of cardiovascular diseases (56,57).

Overall, a comprehensive LM program should be incorporated as part of every weight loss intervention. LM alone may result in weight loss ranging from 1.4% to 8.6% TWL depending on the intensity (56,58,59). Key components to success include a diet plan that patients can adhere to, incorporation of physical activity, and a behavioral treatment plan to reinforce the necessary strategies to maintain the lost weight.


Weight-loss medications may be considered when patients fail to respond to lifestyle modification and have a BMI of ≥30 or ≥27 kg/m2 with obesity-related comorbidities (8,60). Before initiation of a weight-loss medication, current medications should be reviewed to identify any that are associated with weight gain and should be substituted with more weight-neutral medications (Table 2). To date, there are 5 antiobesity medications approved by the Food and Drug Administration (FDA)—phentermine, orlistat (Xenical), phentermine/topiramate (Qsymia), naltrexone/bupropion (Contrave), and liraglutide (Saxenda) (Table 5). With the exception of orlistat, which blocks absorption of 25%–30% of fat calories, these medications target appetite mechanisms specifically by working in the arcuate nucleus to stimulate pro-opiomelanocortin neurons to promote satiety. It is important to discuss both potential benefits and adverse events of each medication before its initiation and to document the conversation, especially when the medication is used off-label. Furthermore, pregnancy is contraindicated for all weight-loss medications, and patients should be advised to use dual contraceptive methods.

Table 5.
Table 5.:
Commonly prescribed obesity medications
Table 5-A.
Table 5-A.:
Commonly prescribed obesity medications

Although there is no generalizable hierarchical algorithm for medication selection, specific medications are preferred in certain clinical settings based on efficacy, adverse events, warnings, contraindications, organ clearance, and mechanisms of action (61). For example, phentermine/topiramate should be considered in patients with migraine, bupropion/naltrexone for those with smoking or depression history, and liraglutide for those with diabetes/prediabetes. In addition, certain medications should be avoided in patients with specific comorbidities. For example, patients with uncontrolled hypertension or a history of heart disease should not be prescribed phentermine. Patients with an elevated seizure risk should avoid bupropion/naltrexone.

An effective response is defined as ≥5% TWL at 3 months after the initiation of a weight-loss medication. If the response is deemed ineffective (<5% TWL at 3 months) or if safety or intolerability issue arises, the medication should be discontinued and switched to an alternative medication or treatment approach (26).

Gelesis100 is a procedureless intervention that was FDA-approved based on pharmacotherapy thresholds and represents a new class of obesity treatments. It is a hydrogel capsule that is orally administered with water before a meal. When hydrated, Gelesis100 occupies about one-fourth of the gastric volume. The particles maintain their gel form while passing through the small intestine before breaking down in the colon. A pivotal trial (GLOW trial) randomized 436 patients to Gelesis100 vs placebo. At 6 months, the Gelesis100 group experienced 6.4% TWL (vs 4.4% TWL for placebo), with 59% achieving ≥5% TWL (62). This technology is not yet commercially available.

In addition to the medications listed above, there are several antiobesity agents under development and currently undergoing clinical trial. For a new drug to be approved for weight loss, it must meet the FDA thresholds, defined as significant placebo-adjusted weight loss of ≥5% TWL at 1 year or ≥35% of patients achieving ≥5% TWL (which must be at least twice that induced by placebo).

Bariatric Endoscopy

Bariatric endoscopy may be divided into gastric and small bowel interventions (63,64). In general, gastric interventions primarily induce weight loss with secondary effects on metabolic conditions. By contrast, small bowel interventions have direct effects on metabolic conditions with or without weight loss. To date, there are 3 types of bariatric endoscopic devices that are FDA-approved and available (Figure 1).

Figure 1.
Figure 1.:
Primary bariatric endoscopic interventions. BMI, body mass index; GI, gastrointestinal; ITT, Intention-to-treat; TWL, total weight loss.

Intragastric balloons occupy space in the stomach and seem to alter gastric motility (65). There currently are 2 IGBs available in the United States—Orbera (Apollo Endosurgery, Austin, TX) and Obalon (Obalon Therapeutics, Carlsbad, CA). Orbera is a single fluid-filled balloon that is placed and removed endoscopically at 6 months. Obalon is a 3-balloon system, filled with nitrogen gas, swallowed 4 weeks apart, with positioning confirmed via x-ray or magnetic resonance. All balloons are removed endoscopically at 6 months. An Orbera meta-analysis (17 studies/1,638 patients) demonstrated an 11.3% TWL at 12 months. The most common AEs were pain and nausea (33.7%). The severe adverse event (SAE) rate was 1.6%, including migration (1.4%), perforation (0.1%), and death (0.08%) (66). For Obalon, a randomized sham-controlled trial revealed a 6.9% TWL at 12 months with an SAE rate of 0.4% (67). However, the real-world experience (1,343 patients) showed a 10% TWL with an SAE rate of 0.15% including severe abdominal pain and gastric perforation (68).

Gastric remodeling may be performed via endoscopic suturing or plication and dates back to as early as 2008 (69–71). Currently, there are 2 devices that are cleared by the FDA for tissue approximation and are used for this purpose, however, without specific weight loss claims—Overstitch (Apollo Endosurgery) and Incisionless Operating Platform (USGI Medical, San Clemente, CA). Endoscopic sleeve gastroplasty is the most common gastric remodeling procedure that involves placing several sutures in a running fashion along the greater curvature. A second layer of sutures may also be placed medially for reinforcement (72). A meta-analysis (8 studies/1772 patients) revealed its efficacy to be 16.5% TWL at 12 months and an SAE rate of 2.2% including pain/nausea, bleeding, perigastric leak, and fluid collection (73). At 5 years, a single center study (56 of 68 patients who were eligible for the 5-year follow-up from the original cohort of 216 patients) revealed a 15.9% TWL (compared with 15.6% at 1 year) (74). In comparison, gastric plication, also known as Primary Obesity Surgery Endoluminal (POSE), involves placement of tissue plications in the stomach. In contrast to endoscopic sleeve gastroplasty which may be endoscopically reversible, POSE focuses on serosal apposition and is not reversible. The traditional POSE procedure involves placement of plications primarily in the fundus (75). A more recent pattern, also known as distal POSE or POSE2, however, involves placement of plications solely in the gastric body (76–78). A meta-analysis (5 studies/586 patients) demonstrated that traditional POSE was associated with 12.1% and 13.2% TWL at 6 and 12–15 months, respectively, with an SAE rate of 3.2% including chest pain, low-grade fever, extragastric bleeding, and hepatic abscess (79). With the new plication pattern, the efficacy seemed to be higher with approximately 15% and 17.5% TWL at 6 and 9 months, respectively (76–78,80). Preliminary results suggest that patients with class III obesity may experience greater weight loss (19-20% TWL at 1 year) following ESG or distal POSE compared to those with class I and II (80,81).

Aspiration therapy removes a portion of food from the stomach after ingestion. The system consists of a large fenestrated gastrostomy tube (A-tube), an external port at the skin for aspiration, and a portable device to perform aspiration. The A-tube is placed endoscopically via a standard pull technique, and the port is attached at 1–2 weeks. A meta-analysis (5 studies/590 patients) demonstrated a 17.8% TWL at 1 year with an SAE rate of 4.1% including buried bumper, peritonitis, abdominal pain, and product malfunction (82).

In addition to weight loss efficacy, all of the approved gastric devices and/or procedures discussed above have been shown to improve obesity-related comorbidities, such as diabetes and fatty liver (82–86). The effect of endoscopic bariatric procedures on conception, however, remains unknown.

Other gastric devices including the Spatz and Elipse balloon systems are currently undergoing FDA review, whereas some small bowel interventions such as duodenal-jejunal bypass liner and duodenal mucosal resurfacing are undergoing US clinical trials. According to the ASGE/ASMBS, a new endoscopic procedure intended as a primary obesity intervention should achieve ≥25% excess weight loss (EWL) at 1 year with a minimum of 15% EWL over control with an SAE rate <5% (87).

Bariatric surgery

Bariatric surgery should be considered for patients with a BMI of ≥40 or ≥35 kg/m2 with at least 1 comorbidity (88). Although several bariatric surgical procedures are available (Figure 2), SG and RYGB remain the most commonly performed.

Figure 2.
Figure 2.:
Bariatric surgeries. Outcome data from meta-analyses or largest available series. DI, duodeno-ileal; EWL, excess weight loss; GEJ, gastroesophageal junction; GJA, gastrojejunal; ICV, ileocecal valve; II, ileoileal; JJA, jejunojejunal; PE, pulmonary embolism; SBO, small bowel obstruction; TWL, total weight loss.

SG involves removal of the fundus and greater curvature to create a tubular structure along the lesser curvature. The small bowel remains unaltered. A meta-analysis (11 studies/over 3,000 patients) revealed that patients experienced 51.5% EWL at 1 year. The pooled mortality rate was 0.6% with an AE rate of 8.9% and reoperation rate of 3% (89). In a single center study, 51 of the original cohort of 165 patients experienced 60.5% EWL at 5 years (compared with 82% EWL at 1 year) (90).

RYGB is the preferred surgery for patients with obesity and concomitant metabolic diseases or gastroesophageal reflux disease. During RYGB, the stomach is divided into a small pouch and a larger remnant stomach. The jejunum is transected, followed by connecting one end to the pouch at the gastrojejunal anastomosis and the other end to the proximal jejunum at the jejunojejunal anastomosis. A meta-analysis (17 studies/over 8,000 patients) revealed that patients experienced 63.3% EWL at 1 year after RYGB. The pooled mortality rate was 1.1% with an AE rate of 12% and reoperation rate of 5.3% (89). At 12 years, the average weight loss is 27% TWL (n = 387) (91).

In addition to SG and RYGB, other procedures that are still being performed at a smaller proportion include gastric banding and biliopancreatic diversion with duodenal switch. Furthermore, there are several emerging procedures, such as minigastric bypass and single anastomosis duodenoileal bypass with sleeve gastrectomy, which gastroenterologists should become familiar with (Figure 2).


As the number of bariatric surgeries continues to rise, gastroenterologists will see more patients with surgically altered anatomy. In addition to understanding normal and abnormal endoscopic findings in this patient population (see above), gastroenterologists should be familiar with potential complications and their management. Table 6 summarizes complications after each of the common bariatric surgeries, presenting symptoms, and management strategies (92). Furthermore, nutrient deficiencies may be seen after all bariatric surgeries, such as vitamins B1/B12, D, A, folate, iron, and calcium, with the addition of zinc and copper for biliopancreatic diversion with duodenal switch and RYGB (93,94). Therefore, adherence to vitamin supplements should be assessed with a low threshold to check these levels, especially for those who are not routinely followed by bariatric surgery. In addition, weight regain after bariatric surgery is not uncommon and is likely caused by several etiologies including medical, behavioral, hormonal, pharmacologic, and anatomical factors. Gastroenterologists should routinely ask for prebariatric surgical, nadir, and current weights. If weight regain is encountered, referral to a multidisciplinary team, including dietitian, obesity medicine expert, bariatric endoscopist, and bariatric surgeon, for consideration of pharmacotherapy and/or endoscopic revision of bariatric surgery is recommended. There are several effective endoscopic treatment options for weight regain; however, this is beyond the scope of this article.

Table 6.
Table 6.:
Complications of common bariatric surgeries


There are several resources available for gastroenterologists who plan on specializing in Obesity Medicine and Bariatric Endoscopy (95). These programs focus on cognitive elements, skill set development, and center requirements. American Board of Obesity Medicine credentialing is also available for board-certified gastroenterologists without the need for additional training.

From a center standpoint, there are also several infrastructure and personnel considerations. These include having a patient-friendly waiting area (such as wide chairs and reinforced toilets) and medical equipment (such as extra-large blood pressure cuffs and bariatric scales). Staff training to reduce bias and stigma and to encourage the use of people-first language and terms such as unhealthy weight rather obese is also encouraged. Furthermore, a multidisciplinary team, which includes bariatric surgeons, bariatric endoscopists, obesity medicine experts, dietitians, psychologists, health coaches, and/or social workers, is essential and can be assembled with the help of modern virtual platforms. In addition, these platforms may be used as part of the aftercare program. Moreover, fitness applications and calorie tracking devices may be useful to encourage adherence to LM.


Gastroenterologists will continue to see an increasing number of patients with obesity. These patients are at greater risk of GI comorbidities and require special consideration. Similarly, bariatric surgery carries various complications that necessitate unique management strategies. Finally, gastroenterologists are well positioned to manage obesity medically and endoscopically and should adopt a greater role in addressing this pandemic.


Guarantor of the article: Christopher C. Thompson, MD, MSc.

Specific author contributions: P.J.: wrote the manuscript. C.C.T.: critically reviewed the article for important intellectual content. All authors approved the final draft of the article.

Financial support: NIH T32 DK007533 and P30 DK034854.

Potential competing interests: P.J. has received research support from Apollo Endosurgery - Research Support, Boston Scientific - Research Support, Endogastric Solutions - Consultant, Fractyl - Research Support, GI Dynamics - Consultant (Consulting fees), Research Support, Lumendi - Consultant. C.C. Thompson: Apollo Endosurgery - Consultant/Research Support (Consulting fees/Institutional Research Grants), Aspire Bariatrics - Research Support (Institutional Research Grant), BlueFlame Healthcare Venture Fund - General Partner, Boston Scientific - Consultant (Consulting fees)/Research Support (Institutional Research Grant), Covidien/Medtronic - Consultant (Consulting fees), EnVision Endoscopy - Board Member, ERBE - Institutional Research Grant, Fractyl - Consultant/Advisory Board Members (Consulting fees), FujiFilm - Institutional Research Grant, GI Dynamics - Consultant (Consulting fees)/Resaerch Support (Institutional Research Grant), GI Windows - Ownership Interest, Lumendi - Consultant/Institutional Research Grant, Olympus/Spiration - Consultant (Consulting fees)/Research Support (Equipment Loans), USGI Medical - Consultant (Consulting fees)/Advisory Board Member (Consulting fees)/Research Support (Institutional Research Grant)


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