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Chapter Objectives

  1. 1.

    To report the high level of evidence studies regarding efficacy of metabolic procedures in treatment of type 2 diabetes mellitus (T2DM)

  2. 2.

    To present and compare established and novel gastrointestinal procedures aimed at controlling T2DM

  3. 3.

    To overview underlying mechanisms for improvement of T2DM following metabolic procedures

  4. 4.

    To present published guidelines in the field of metabolic surgery

Introduction

The growing intertwined pandemics of obesity and type 2 diabetes mellitus (T2DM) are major global public health threats. Obesity is considered a major contributing factor in the pathogenesis of T2DM, such that more than 80 % of diabetic patients are overweight or obese. Although lifestyle modifications and pharmacotherapy are the cornerstone for treatment of obesity and T2DM, adequate glycemic control is not obtained in most obese patients with T2DM. In addition to achieving substantial and long-lasting weight loss, bariatric procedures cause amelioration, and even complete remission, of T2DM in a substantial number of severely obese patients. No other currently available intervention has been shown to have an ability to provide complete remission of this progressive disease. Although long-term durability of diabetes remission following bariatric surgery has yet to be validated by multiple studies, long-term improved glycemic control resulting from surgery may result in less end-organ damage, even if there is an eventual relapse [1–6].

Bariatric surgery is not only considered an extremely effective therapeutic intervention in T2DM, but it also prevents the development of diabetes in the severely obese population. A recent longitudinal study, Swedish Obese Subjects Study, compared the incidence of T2DM between 1,658 patients who underwent bariatric surgery and 1,771 obese matched controls, none of whom had diabetes at baseline. During the follow-up period of 15 years, bariatric surgery, as compared with standard care, reduced the incidence of T2DM by 78 %, and diabetes did not develop in approximately 10 of 13 obese patients who underwent bariatric surgery [7].

In addition to impressive antidiabetic effects, bariatric surgeries are associated with other favorable metabolic outcomes including resolution or improvement of metabolic syndrome, hypertension, dyslipidemia, and improved overall survival. In light of such dramatic metabolic impacts of these procedures, many which may be independent of weight loss, the term “metabolic surgery” is favored over “bariatric surgery” especially when the primary goal of surgical treatment is to improve diabetes [1–6].

Considering the mounting worldwide enthusiasm for metabolic surgeries, the Diabetes Surgery Summit published the first consensus guidelines for the use and study of metabolic surgery in 2010. The recommendations were made by a multidisciplinary group of 50 voting international experts (Table 29.1) [2]. A year later, the International Diabetes Federation released its position statement on the role of surgery and other gastrointestinal interventions in the treatment and prevention of T2DM (Table 29.2) [1]. Both documents provide practical recommendations for clinicians who treat diabetic patients [1, 2].

Table 29.1 Diabetes Surgery Summit Consensus Guidelines [2]
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Table 29.2 International Diabetes Federation Recommendations for Management of T2DM [1]
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Currently, metabolic operations are considered an appropriate treatment for diabetic patients with body mass index (BMI) ≥ 35 kg/m2, especially those with other weight-related comorbidities such as hypertension and dyslipidemia, who are acceptable surgical candidates and have not responded adequately to nonsurgical management (i.e., glycated hemoglobin >7 % despite of conventional therapies). Since T2DM has a progressive course and severely obese diabetic patients are often refractory to conventional therapies secondary to severe insulin resistance, metabolic operations should be considered earlier in the treatment plan of diabetics [1–4]. According to the International Diabetes Federation, for Asian and some other ethnicities of increased risk, BMI action points may be reduced by 2.5 kg/m2 [1].

Standard Metabolic Procedures

The International Diabetes Federation places emphasis on performing metabolic operations in high-volume centers with multidisciplinary teams that are experienced in the management of obesity and diabetes. Surgeons must have undertaken relevant supervised training and attained specific clinical expertise for each surgical procedure [1].

The International Diabetes Federation has considered Roux-en-Y gastric bypass (RYGB), laparoscopic adjustable gastric banding (LAGB), sleeve gastrectomy (SG), biliopancreatic diversion (BPD), and the duodenal switch variant (BPD-DS) as currently accepted metabolic operations. Vertical banded gastroplasty (VBG) has fallen out of favor because of suboptimal long-term results. The first two procedures have been considered acceptable procedures in adolescents [1]. Of note, variations in the steps of each procedure are associated with dissimilar metabolic responses. For example, the size of the gastric pouch and gastrojejunostomy anastomosis, placement of a band around the anastomosis, and the length of the limbs may affect metabolic outcomes after RYGB [8].

The morbidity and mortality rate associated with metabolic operations is generally low. It has been shown that the laparoscopic approach is associated with fewer postoperative complications than the open approach, most notably the risk of wound infection and incisional hernia [3, 4, 9]. Robotic and single incision laparoscopic approaches are considered emerging platforms in the field of bariatric and metabolic surgery with benefits and limitations that are not yet clear.

Outcomes

Several observational and nonrandomized trials have demonstrated marked and sustained improvement in T2DM in both morbidly obese and less obese patients following metabolic operations. Since the studies in this field are heterogeneous with inconsistent methodologies for inclusion criteria (e.g., duration or severity of T2DM), measurement of outcomes, definition of remission, and direct comparison of results are difficult [3–6, 10].

Meta-analyses involving more than 100 studies have shown an 80 % early complete remission of T2DM and 75 % persistent remission more than 2 years after surgery. The beneficial effects on hypertension and dyslipidemia were also impressive (Table 29.3) [11, 12].

Table 29.3 Efficacy of standard metabolic operations according to the two meta-analyses
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High Level of Evidence Studies Comparing Metabolic Surgery Versus Conventional Therapy for T2DM

A growing body of evidence derived from recent randomized controlled trials has demonstrated superiority of bariatric surgery over conventional medical therapy for management of T2DM (Table 29.4) [13–15].

Table 29.4 High level of evidence studies on metabolic surgery versus conventional medical therapy for type 2 diabetes
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Schauer et al. randomized 150 obese patients with poorly controlled T2DM to receive intensive medical therapy alone, including newer agents such as incretin analogues, versus medical therapy plus RYGB or SG (Table 29.4). More than one-third of patients (36 %) had a BMI less than 35 kg/m2. After 12 months, medical therapy plus metabolic surgery achieved glycemic control in significantly more patients than with medical therapy alone. Homeostasis model assessment of insulin resistance (HOMA-IR) improved significantly after each of the two surgical procedures, as compared with medical therapy alone. The use of drugs to lower glucose, lipid, and blood pressure levels decreased significantly after both surgical procedures, but increased in patients on medical therapy alone [13].

A randomized controlled trial of 60 severely obese diabetic patients by Mingrone et al. reported that RYGB and BPD were associated with an increased rate of remission of T2DM (relative risk, 7.5 and 9.5, respectively) and significant reduction in glycated hemoglobin as compared with medical therapy after 2 years (Table 29.4). The beneficial effects of surgery on the lipid profile were also significant; total cholesterol levels normalized in 100 % and 27 % in the surgical and medical groups, respectively [14].

Dixon et al. compared LAGB with conventional medical therapy in obese patients with newly diagnosed T2DM (<2 years) of mild severity (glycated hemoglobin <7.5 %) (Table 29.4). This randomized controlled trial demonstrated surgical weight loss was more effective than best medical management in terms of weight loss, glycemic control, and diabetes remission rates. Resolution of components of the metabolic syndrome and reduction in antidiabetic, antihypertensive, and cholesterol-lowering medications were also seen in the surgical arm [15].

The Swedish Obese Subjects Study, a large nonrandomized prospective trial with long follow-up time, also clearly showed higher diabetes remission rates after surgery (>68 % VBG) but with gradual recurrence over time in some patients (Table 29.4). The proportion of patients with remission of T2DM at 2 and 10 years following bariatric operations was 72 and 36 %, respectively [16].

High Level of Evidence Studies Comparing Two Metabolic Surgical Procedures

Currently, a relative paucity of high-quality studies comparing surgical procedures head to head is available to clearly define the efficacy of different metabolic operations (Table 29.5) [1, 2, 10]. The operations differ in the degree of benefit they impart on an individual’s state of metabolic derangement, with diversionary procedures demonstrating more profound effects, at least initially, than non-diversionary procedures [1–6].

Table 29.5 High level of evidence studies comparing two metabolic surgical procedures
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Large meta-analyses reported that BPD, with and without duodenal switch, was associated with a 95 % resolution of T2DM, gastric bypass was associated with 80 % resolution, and gastric banding with 57 %. The beneficial effects of various procedures on control of hypertension and dyslipidemia were also relatively parallel to the effects on diabetes. The procedures that produced greater excess weight loss led to higher resolution of metabolic disease (Table 29.3). Despite of the large sample size, the studies included in these meta-analyses were largely retrospective and single armed [11, 12].

Two randomized controlled trials compared metabolic outcomes following gastric bypass and SG (Table 29.5) [13, 18]. Lee et al. reported that the remission rate of T2DM and metabolic syndrome after laparoscopic mini-gastric bypass (i.e., a 2-cm wide gastric tube along the lesser curve with loop gastrojejunostomy 120 cm distal to the Treitz ligament) was significantly higher to that after SG [18]. In the Schauer et al. study, the proportion of patients with resolution of T2DM following RYGB and SG was 42 and 27 %, respectively; however, the differences did not reach statistical significance (Fig. 29.1).

Fig. 29.1
figure 1

Change in glycated hemoglobin during 1 year of follow-up (Reprinted with permission from Schauer et al. [13])

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In comparison to the RYGB, despite a similar effect on weight loss, a higher rate of diabetes remission was reported following BPD (Table 29.5 and Fig. 29.2) [14]. Conversely, the remission rate of T2DM was lower following LAGB than with a RYGB (Table 29.5 and Fig. 29.3) [19].

Fig. 29.2
figure 2

Glycated hemoglobin level during 2 years of follow-up (Reprinted with permission from Mingrone et al. [14])

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Fig. 29.3
figure 3

Kaplan-Meier curve for time to remission of T2DM over a 3-year period. (Reprinted with permission from Pournaras et al. [19])

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In terms of beneficial effects on lipid profile, a randomized trial reported an average of 20 mg/dL greater reduction in low-density lipoprotein (LDL) cholesterol levels after BPD-DS as compared with a RYGB [21]. Similarly, in Mingrone et al.’s clinical trial, LDL cholesterol was significantly lower among patients who underwent BPD than among those who underwent RYGB [14]. RYGB, however, had greater impact on raising high-density lipoprotein (HDL) cholesterol than BPD, with or without duodenal switch [14, 21].

A randomized clinical trial by Pinheiro et al. addressed the effect of length of Roux-en-Y on the resolution of T2DM in super-obese patients (Table 29.5). This study randomized 105 patients with BMI of 50 kg/m2 to a long limb (50-cm biliary limb and 150-cm Roux limb) or a longer limb (100-cm biliary limb and 250-cm Roux limb) gastric bypass. The latter group achieved greater diabetes control (93 % versus 58 %) and lipid disorder improvement (70 % versus 57 %) despite similar weight loss [20].

Although the aforementioned clinical trials demonstrate the presence of an antidiabetic efficacy gradient among standard metabolic operations (BPD > RYGB > SG > LAGB), the true prioritization of the procedure that would be the best choice for different patient conditions awaits further high-quality comparative studies with larger sample size and longer follow-up time [1, 2].

Metabolic Surgery in Patients with BMI <35 kg/m2

The observation of diabetes remission following gastrectomy performed for gastric ulcer and cancer in nonobese patients dated back to more than 50 years ago. In recent years, several case series have reported the impressive metabolic effects in less obese and even nonobese patients after standard and novel metabolic procedures. A recent review of 18 studies showed a significant reduction in mean fasting plasma glucose (from 203 to 112 mg/dL) and glycated hemoglobin (from 9.0 to 6.3 %) after surgery [22]. On average, 87 % of the patients stopped taking antidiabetic medications following surgery. Metabolic surgery also provided desirable weight loss results. The mean BMI categorized as class I obesity prior to surgery reached normal weight range after surgery (from 30.4 to 24.8 kg/m2). Less than 3 % of patients developed excessive weight loss and they did not show any evidence of malnutrition. Even the procedures that typically lead to profound weight loss in morbidly obese patients, such as BPD, did not entail the risk of excessive weight loss in less obese patients.

According to the statements of the International Diabetes Federation, Diabetes Surgery Summit, and American Society for Metabolic and Bariatric Surgery, metabolic surgery may be an appropriate therapeutic alternative in carefully selected type 2 diabetic patients with a BMI between 30 and 35 kg/m2 who do not respond to fully optimized medical therapy (i.e., glycated hemoglobin >7.5 %), especially in the presence of other weight-responsive comorbidities [1, 2, 23]. Among the established metabolic procedures, the Diabetes Surgery Summit guideline suggests RYGB in this setting [2].

Operation of Choice

The four standard metabolic procedures have their own risks and benefits. More extensive procedures, such as BPD, are generally associated with greater weight loss and more profound metabolic effects but at the cost of more surgical complications (Table 29.6) [1–4, 8].

Table 29.6 Summary of outcomes after standard metabolic operations
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The choice of metabolic surgery requires precise assessment of risk versus benefit for each operation and must be individualized for each surgical candidate. The International Diabetes Federation presented a list of factors to consider when choosing a metabolic procedure [1]:

  • Expertise and experience in bariatric surgical procedures

  • The patient’s preference (when the range of risks and benefits, the importance of compliance, and the effects on eating choices and behaviors have been fully described)

  • The patient’s general health and risk factors associated with high perioperative morbidity and mortality

  • The simplicity and reversibility of a procedure

  • The duration of T2DM and the degree of apparent residual beta cell function

  • The follow-up regimen for the procedure and the commitment of the patient to adhere to it

Mechanism of Action

The precise mechanisms for restoration of euglycemia after metabolic operations have only been partly elucidated [3, 4, 24–29]. The available evidence responsible for diabetes control following standard metabolic operations has been summarized in Fig. 29.4. The brief explanation of the underlying mechanisms is presented here (the steps indicated correspond with the numbers in Fig. 29.4):

Fig. 29.4
figure 4

Mechanism of action of standard metabolic operations

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  • Restrictive component of all types of standard metabolic procedures physically restricts meal size (step 1).

  • Malabsorptive components of RYGB and BPD further reduce caloric intake (step 2).

  • All metabolic operations also attenuate appetite despite reduced caloric intake and weight loss. Conversely, weight loss induced by nonsurgical approaches activates physiological responses that lead to compensatory hunger and tendency to weight gain. Activation of satiety mechanisms plays an important role in maintaining weight loss following surgery (step 3) [3, 25].

  • Ghrelin, a potent appetite stimulant hormone mainly produced in the fundus of the stomach, is decreased following SG and RYGB (step 4). Conversely, most studies have reported increase in ghrelin levels after LAGB. The latter procedure preserves the stomach intact (in contrast to SG) and does not exclude the major ghrelin-producing cells of fundus from contact with food (in contrast to RYGB). Therefore, similar to diet-induced weight loss, ghrelin levels are increased after LAGB in response to the energy restriction. Despite the compensatory increase of ghrelin levels following LAGB, appetite is reduced and the sensation of fullness is increased secondary to the appropriate tightness of the band, which activates vagally innervated gastric mechanoreceptors. The reported effects of BPD on ghrelin are inconsistent [25, 26].

  • The net effect of the aforementioned mechanisms is reduction in energy intake and subsequently weight loss (step 5), which leads to the following results:

  • Acute caloric restriction immediately after surgery improves the glycemic control transiently (step 6) [24, 25].

  • Decreased energy intake within a few days following metabolic operations and before substantial weight loss reduces liver fat and leads to the reduction in the hepatic glucose output (step 7) [24].

  • Ectopic accumulation of triglycerides outside of the adipose tissue (e.g., in the liver, skeletal muscle, pancreatic beta cells) provides an intracellular source of fatty acids in excess of the oxidative needs of the cell. The surplus fatty acyl CoA may enter the non-oxidative metabolic pathways believed to be responsible for cell dysfunction (i.e., lipotoxicity) and, ultimately, lipoapoptosis. Lipotoxicity of liver and skeletal muscles damages the insulin-signaling cascade and has been identified as one of the mechanisms of obesity- associated insulin resistance. Metabolic operations reduce this deleterious effect and significantly increase insulin sensitivity even before BMI normalization (step 8). Pancreatic beta cell lipoapoptosis can also be prevented by caloric restriction (step 9) [30].

  • Obesity is considered a state of chronic low-grade inflammation. Adiponectin and leptin are members of the adipocyte-secreted proteins termed “adipocytokines” or “adipokines,” which are involved in several pathophysiological processes such as inflammation and insulin sensitivity. When total fat mass increases, leptin and inflammatory mediators including C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) are produced in higher quantities, but adiponectin synthesis is reduced. The resultant proinflammatory environment negatively affects insulin-signaling pathways and leads to insulin resistance. Loss of fat mass following metabolic operations normalizes inflammatory cytokines and adipokines (step 10) and improves insulin sensitivity (step 11). In addition, reduction in leptin and inflammatory cytokines results in better pancreatic beta cell function (step 12) and survival (step 13) [3, 24, 27, 31].

  • The incretin mechanism for resolution of T2DM following diversionary metabolic operations (e.g., RYGB and BPD) has attracted much interest in recent years. The incretins are gut-derived hormones that are secreted after a meal and are responsible for up to 70 % of postprandial insulin secretion. Rerouting of the gastrointestinal tract following diversionary metabolic operations, with exclusion of the duodenum and proximal jejunum (foregut hypothesis) (step 14), and the rapid exposure of the distal ileum to undigested nutrients (hindgut hypothesis) (step 15), alters secretion of gut hormones including glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and peptide YY (PYY), which positively affects glucose homeostasis. GLP-1, the most studied incretin, improves pattern of insulin secretion (step 16), suppresses glucagon secretion, and possibly enhances peripheral glucose uptake. This peptide, along with PYY, has anorexic effects (step 17) [4, 25, 28]. Recent evidence shows increased nutrient transit and hindgut effects after SG (step 18) [29].

  • GLP-1 can also delay or even reverse the loss of pancreatic islet cell mass by inhibiting apoptosis, stimulating beta cell proliferation, and protecting against oxidative insults (step 19) [28, 32].

While some of the aforementioned mechanisms (e.g., reduction in lipotoxicity, inflammatory state, and insulin resistance) are not considered specific effects of metabolic operations and have also been observed after nonsurgical weight loss, it appears that surgically induced weight loss can expedite and exaggerate those responses. A meta-analysis of published researches on insulin resistance after various types of bariatric procedures showed RYGB and BPD produce an acute decrease in insulin resistance within 2 weeks. SG produced a faster reduction in insulin resistance at 1 month compared to LAGB, where a decrease was significant only at 6 months [33].

In a similar way, although many antidiabetic effects occur after any type of metabolic operations, some of them are seen specifically following diversionary surgeries. Significantly greater remission rates of T2DM after RYGB and BPD compared to other interventions with equivalent weight loss support the importance of such mechanisms. In addition, following RYGB and BPD, diabetes often resolves within several days to weeks, long before substantial weight loss has occurred [4, 25]. One study of 240 diabetic patients who underwent RYGB reported that 30 % of patients were discharged normoglycemic off all diabetes medications after an average postoperative hospital stay of 2.8 days [34]. Such a rapid antidiabetic effect is not observed following purely restrictive operations [4]. More interestingly, the effect of RYGB on insulin sensitivity and secretion seems to differ with BPD. While RYGB enhances insulin secretion more efficiently, the proposed main antidiabetic effect of BPD is related to rapid improvement of insulin sensitivity [35]. Despite the observations that diversionary procedures usually lead to early non-weight-related euglycemia, the amount of weight loss may be the principal factor in the long term [4]. The proposed antidiabetic mechanisms of the standard metabolic procedures are summarized in Table 29.7.

Table 29.7 Summary of the proposed antidiabetes mechanisms of various metabolic operations
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Novel Metabolic Procedures and Devices

Several novel procedures and devices, aimed to treat T2DM and not to reduce weight, have been developed in recent years. Although the preliminary experimental and limited clinical studies demonstrate promising weight-independent antidiabetic results, their clinical use should still be considered investigational [1, 2].

Duodenal-jejunal bypass (DJB) is a stomach-sparing bypass of the proximal intestine that has comparable limb lengths to the standard RYGB (Fig. 29.5a). The foregut and hindgut hypotheses have been proposed to explain its antidiabetic effects. Since the residual stomach is available for endoscopic examination, it may be considered a good alternative to RYGB in high-risk groups for gastric cancer [3, 4].

Fig. 29.5
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Novel metabolic procedures: (a) duodenal-jejunal bypass, (b) ileal interposition

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In ileal interposition (IT), a small segment of terminal ileum, with intact mesentery and neurovascular supply, is inserted into the proximal jejunum, enhancing its exposure to ingested nutrients. This procedure exaggerates release of incretin hormones without any weight loss effect (Fig. 29.5b). IT requires three anastomoses (versus the two required in RYGB, BPD, and DJB) [3, 4].

DJB and IT may be combined with conventional SG in order to add the beneficial effects of the latter procedure (e.g., restriction of stomach, decreased ghrelin secretion, rapid nutrient transit) on weight and glucose metabolism. Both procedures may also be considered as revisional operations after SG, if it fails to resolve the diabetes.

Laparoscopic gastric plication is gaining traction in the treatment of morbid obesity, as it appears to replicate the results of SG with fewer complications. Laparoscopic adjustable gastric banded plication is also a new restrictive procedure combining adjustable banding and plication of the stomach. Their effect on glycemic control has yet to be clearly defined.

Several novel endoscopically placed devices, which attempt to mimic the putative mechanisms of metabolic surgeries but with a less invasive approach, are under investigation. Intragastric balloons; gastric volume restriction by stapling, suturing, or anchoring (endoluminal gastroplasties); and restrictive valves are examples utilizing the underlying mechanisms of restrictive metabolic surgeries [3, 4].

Endoscopically placed endoluminal liners have been developed for bypass of the duodenum and proximal jejunum (resembling DJB) or for bypass of the stomach, duodenum, and proximal jejunum (resembling RYGB). Both devices are flexible, impermeable plastic sleeves that are anchored in the proximal duodenum and at the level of gastroesophageal junction. Preliminary short-term results of the endoluminal liners, in terms of weight loss and glycemic control, are promising. However, since endoluminal devices are designed to stay in place for 6–12 months, their role in the management of severe obesity and T2DM is limited at this time [3, 4].

Conclusion

Currently, a relative paucity of high-quality comparative trials limits the strength of any recommendations that are essentially opinions of the chapter authors (Table 29.8). Based on available outcome studies, LAGB and SG are the safest procedures but least effective in achieving glycemic control. RYGB carries more risk than LAGB and SG but is much more effective. BPD appears to be the most effective antidiabetic procedure but does carry a higher operative risk, lifelong risk of malnutrition, and potentially significant nutritional deficiencies.

Table 29.8 Choice of metabolic surgery
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In general, the patient’s operative risk is one of the major determinants in the choice of metabolic surgery. While LAGB and SG are appropriate choices in high-risk patients, RYGB is the preferred choice for low- to moderate-risk patients. BPD and BPD-DS may be reasonable options for low- to moderate-risk patients thought to be highly compliant with follow-up regimen and monitoring.

Choice of operation also depends on the extent of disease. In appropriate-risk patients with prediabetes or established T2DM (mild to severe), RYGB is probably the best overall option. For prediabetes and early mild T2DM, LAGB or SG may be reasonable options secondary to RYGB, especially if the risk of surgery is more than usual. Alternatively, BPD and BPD-DS may be more effective in patients with moderate to severe T2DM if they are very compliant and not high risk. These recommendations are subject to change as more comparative studies become available. Future procedure modifications may also affect both safety and efficacy.

The position statements of the Diabetes Surgery Summit (Table 29.1) and the International Diabetes Federation (Table 29.2) on the surgical treatment of T2DM provide practical and evidence-based guidelines on how to best use metabolic surgery in diabetic patients [1, 2]. At this time, they are the most useful summaries, from the evidence available, for health-care providers who manage patients with diabetes.

Question Section

Questions

  1. 1.

    Regarding the surgical treatment of type 2 diabetes mellitus (T2DM), which statement is correct?

    1. A.

      Adequate glycemic control is achievable in most diabetic obese patients with medical management.

    2. B.

      Metabolic surgery should be considered as a last resort in management of T2DM and should be reserved for patients with severe uncontrollable disease.

    3. C.

      Metabolic surgery is not indicated in diabetic patient with BMI <35 kg/m2.

    4. D.

      Metabolic surgery can prevent the development of T2DM in the obese population and also provides complete remission of disease in diabetic patients.

    5. E.

      High relapse rate of T2DM in long term diminishes the benefits of metabolic surgery in most patients.

  2. 2.

    Which efficacy gradient does exist among metabolic procedures for the resolution of T2DM?

    1. A.

      BPD > RYGB > SG > AGB

    2. B.

      RYGB > BPD > SG > AGB

    3. C.

      BPD > SG > RYGB > AGB

    4. D.

      BPD = RYGB > SG = AGB

  3. 3.

    With consideration of risk-benefit ratio, which metabolic surgery would be the most appropriate option in an average-risk patient with T2DM?

    1. A.

      BPD

    2. B.

      RYGB

    3. C.

      SG

    4. D.

      AGB