Clinical Practice Guideline
Obesity Surgery and the Treatment of Metabolic Diseases
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Background: 3.9% of men and 5.2% of women in Germany suffer from second-degree obesity (body mass index [BMI] ≥ 35 to <40 kg/m2), and 6.5 million persons suffer from diabetes. Obesity surgery has become established as a further treatment option alongside lifestyle changes and pharmacotherapy.
Methods: The guideline was created by a multidisciplinary panel of experts on the basis of publications retrieved by a systematic literature search. It was subjected to a formal consensus process and tested in public consultation.
Results: The therapeutic aims of surgery for obesity and/or metabolic disease are to improve the quality of life and to prolong life by countering the life-shortening effect of obesity and its comorbidities. These interventions are superior to conservative treatments and are indicated when optimal non-surgical multimodal treatment has been tried without benefit, in patients with BMI ≥ 40 kg/m², or else in patients with BMI ≥ 35 kg/m² who also have one or more of the accompanying illnesses that are associated with obesity. A primary indication without any prior trial of conservative treatment exists if the patient has a BMI ≥ 50 kg/m², if conservative treatment is considered unlikely to help, or if especially severe comorbidities and sequelae of obesity are present that make any delay of surgical treatment inadvisable. Metabolic surgery for type 2 diabetes is indicated (with varying recommendation grades) for patients with BMI ≥ 30 kg/m², and as a primary indication for patients with BMI ≥ 40 kg/m². The currently established standard operations are gastric banding, sleeve gastrectomy, proximal Roux-en-Y gastric bypass, omega-loop gastric bypass, and biliopancreatic diversion.
Conclusion: No single standard technique can be recommended in all cases. In the presence of an appropriate indication, the various surgical treatment options for obesity and/or metabolic disease should be discussed with the patient.
The increased prevalence of obesity in Germany, particularly among young adults, presents a challenge to the healthcare system with major socioeconomic effects both now and in the future. According to the DEGS1 study (2013), 5.2% of women and 3.9% of men in Germany suffer from second-degree obesity (body mass index [BMI] ≥ 35 to < 40 kg/m2); 2.8% of women and 1.2% of men suffer from third-degree obesity (BMI ≥ 40 kg/m²) (1). It is stated in the German Health Report on Diabetes for the year 2017 that 6.5 million persons in the country now suffer from diabetes, 95% of whom have type 2 diabetes (2).
Surgery for obesity and metabolic disease is less common in Germany than in the neighboring Western European countries (Germany, 10.5 procedures per 100 000 persons per year; Benelux countries, 99.3 procedures per 100 000 per year), and there are also differences across the individual German federal states (Länder) (3).
The currently available nonsurgical treatments for weight reduction bring about sustained weight loss in only a small fraction of the persons treated and do not lower mortality (4). The controversial designation of surgical procedures as a “last resort” no longer appears in the new guideline. Moreover, the expression “bariatric surgery” has been replaced by “obesity surgery” in order to make it clear that such procedures are a treatment for the disease called “obesity.”
Readers are referred to the full guideline text for a discussion of special aspects such as surgery in adolescence or old age, pregnancy, perioperative management, and details of the surgical techniques, and to the guideline report for methodological aspects (5).
The guideline was created in accordance with the S3 guideline specifications of the Association of Scientific Medical Societies in Germany (Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften e. V., AWMF) under the aegis of the Surgical Working Group for the Treatment of Obesity (Chirurgische Arbeitsgemeinschaft für Adipositastherapie, CAADIP) of the German Society of General and Visceral Surgery (Deutsche Gesellschaft für Allgemein und Viszeralchirurgie, DGAV). The guideline was issued by the CAADIP. The German Obesity Society (Deutsche Adipositas-Gesellschaft), the German Diabetes Society (Deutsche Diabetes Gesellschaft), and seven other medical specialty societies and associations were represented on the guideline commission, which also included a patient representative (for a list of delegates, see eTable 1).
A search for relevant publications (April 2009 to March 2016) was conducted in the Medline, Cochrane Library, and Scopus databases. Systematic reviews, meta-analyses, and randomized controlled trials (RCTs) were sought.
The literature search yielded 9099 hits (after the elimination of duplicates); after multilevel screening, 261 were chosen for further evaluation. Priority was given to systematic reviews and meta-analyses. Evidence tables to be used as a foundation for the creation of the guideline were prepared for 56 systematic reviews and meta-analyses, one RCT, and five cohort studies; these tables were then evaluated by the SIGN procedure (6). Details are given in the guideline report (5) and in the eMethods.
Major elements of the guideline and changes since the preceding version
In older guidelines, weight loss was often said to be the therapeutic objective of obesity surgery. Nonetheless, empirical data on weight loss in kilograms, BMI points, or percentage excess weight loss (%EWL) do not adequately reflect whether the treatment has really achieved its objective.
The newly formulated objective of obesity surgery and metabolic procedures is to bring about a sustained loss of weight and, through the beneficial effects of weight loss, to achieve the following:
- Better quality of life
- Remission, improvement, and/or prevention of the comorbidities and sequelae of obesity
- Longer survival
- Continued participation in work and in social and cultural activities.
The goals of treatment should always be individually defined and adapted to any changes that take place. This formulation met with a strong consensus among the experts.
Definition of centers
The Barmer Health Report (9) and current German registry data (10) reveal that perioperative morbidity and mortality are lower in certified centers (e.g., 30-day mortality after Roux-en-Y gastric bypass: 0.2% in certified centers, 0.5% in uncertified centers, p = 0.002). There are also differences between the various types of certified center. For example, morbidity was lower in reference and excellence centers than in competence centers (10). To take due account of these data (even though their evidential quality is not high), the guideline commission decided to introduce the new category of “centers with special expertise.” Such centers are supposed to be certified by a specialty society, and the experience of the responsible surgeon should comprise at least 300 obesity operations.
There was a strong consensus among the experts that the following types of patients should undergo surgery only in a center with special expertise, and that the specified techniques should only be performed in such centers (however, this is not evidence based):
- Patients under age 18, or aged 65 and above
- Patients at elevated risk with severe comorbidities (American Society of Anesthesiologists [ASA] score >3)
- Patients with BMI ≥ 60 kg/m²
- Distal bypass operations, conversion operations, and redo operations
- Procedures that are primarily for the treatment of metabolic disease (in patients with BMI <40 kg/m², in collaboration with a physician who is an expert in the treatment of diabetes/a diabetologist).
The treating team that establishes the indication for surgery should consist of the following members:
- A surgeon with competence in the surgical treatment of obesity and metabolic disorders
- An internist/general practitioner/physician with special expertise in nutrition who has competence in the surgical treatment of obesity and metabolic disorders
- A mental health professional with experience in obesity surgery
- A nutritionist or physician with special expertise in nutrition who has experience in obesity surgery
- A physician who is an expert in the treatment of diabetes/a diabetologist, if surgery for metabolic indications (type 2 diabetes) is to be performed.
The term “obesity surgery” refers to any operation (e.g., sleeve gastrectomy) that is intended to bring about sustained weight loss and thereby prevent or improve obesity-associated comorbidities and improve the patient’s quality of life. The recommendations of the current guideline of the German Obesity Society (Deutsche Adipositas-Gesellschaft) (11) and of the American guideline (12) have been adopted.
Obesity surgery is indicated in the following situations:
- In patients with BMI ≥ 40 kg/m2 without any comorbidities or contraindications, when conservative treatment options have been exhausted and after the patient has been thoroughly informed.
- In patients with BMI ≥ 35 kg/m2, after the exhaustion of conservative treatment options, in the presence of one or more obesity-associated comorbidities, such as: type 2 diabetes, coronary heart disease, congestive heart failure, hyperlipidemia, arterial hypertension, nephropathy, obstructive sleep apnea syndrome (OSAS), obesity-hypoventilation syndrome, Pickwick syndrome, non-alcoholic fatty liver disease (NAFLD) or non-alcoholic steatohepatitis (NASH), pseudotumor cerebri, gastro-esophageal reflux disease (GERD), asthma, chronic venous insufficiency, urinary incontinence, immobilizing joint disease, impaired fertility, or polycystic ovarian syndrome.
- A primary indication for obesity surgery (i.e., without any requirement for prior exhaustion of conservative treatment modalities) exists if one of the following conditions is present:
– BMI ≥ 50 kg/m2,
– Whenever, in a specific case, the multidisciplinary team considers a trial of conservative treatment to have little or no chance of success, and
– Whenever especially severe comorbidities and sequelae of obesity are present that make any further delay before surgery inadvisable.
Points 1 and (in part) 2 in the above list of obesity surgery indications are supported by evidence of the highest level (point 2 with respect to the therapeutic objective of weight control and improvement in biochemical markers of cardiovascular risk) and correspondingly, recommendations of the highest grade are given. A strong consensus supported all of the other points.
The exhaustion of conservative treatment is defined as follows, for the purpose of determining the indication for obesity surgery: if the patient has been unable to achieve a loss of >15% of the initial weight (BMI 35.0–39.9 kg/m²), or >20% of the initial weight (BMI ≥ 40 kg/m²), despite having undergone a comprehensive lifestyle intervention for at least 6 months within the past two years, then conservative treatment is considered to have been exhausted.
An indication is also present if this degree of weight loss has indeed been reached, but obesity-associated illnesses persist that could be improved by obesity surgery, or by surgery for a metabolic indication (i.e., type 2 diabetes). Likewise, if initially successful weight reduction has been followed by weight gain of more than 10%, then conservative treatment is considered to have been exhausted.
If a primary indication is present, then the patient’s adherence to treatment regimens should be considered before any procedure is carried out. The patient should change his/her nutrition and eating habits in a manner appropriate to the coming operation for the treatment of obesity.
The expression “surgery for a metabolic indication” or “metabolic surgery” refers to the same surgical procedures that are performed to treat obesity when they are performed primarily in order to improve glycemic metabolism in patients with pre-existing type 2 diabetes.
In its recommendations on the indications for the surgical treatment of type 2 diabetes mellitus (“metabolic surgery”), the guideline commission adopted the recommendations of the American Diabetes Association’s Standards of Medical Care in Diabetes—2017 (13) and of the “Joint Statement by International Diabetes Organizations” (14).
The existing evidence is inadequate to support an indication for the surgical treatment of other “metabolic” disturbances associated with obesity (e.g., dyslipidemias, hypertension).
Surgery is indicated to treat a metabolic disturbance in the following situations:
- Metabolic surgery should be recommended as a primarily indicated treatment option, as defined above, to patients with type 2 diabetes who also have a BMI ≥ 40 kg/m², as such patients stand to benefit both from the antidiabetic effect and from the weight-reducing effect of the intervention.
- Metabolic surgery should be recommended as a potential treatment option to patients with type 2 diabetes whose BMI lies in the range of ≥ 35 kg/m² to <40 kg/m² if their individual target values, as determined from the National Disease Management Guideline on the Treatment of Type 2 Diabetes, have not been achieved.
- Metabolic surgery can be considered for patients with type 2 diabetes whose BMI lies in the range of ≥ 30 kg/m² to <35 kg/m² if their individual target values, as determined from the National Disease Management Guideline on the Treatment of Type 2 Diabetes, have not been achieved.
The first two points above are supported by evidence of the highest level, and there was a strong consensus for all recommendations.
The background for these recommendations is the fact that patients with type 2 diabetes stand to benefit doubly from the intervention, i.e., both by losing weight and by experiencing an improvement or even a remission of their diabetes. Many studies of high quality (RCTs and meta-analyses) have shown the superiority of surgery over conservative treatment in these situations, justifying the recommendations above (15).
Zhang et al., in a meta-analysis of 21 studies, found a significant advantage of Roux-en-Y gastric bypass (RYGB) over sleeve gastrectomy (SG) with respect to the rate of remission of type 2 diabetes (odds ratio [OR] = 3.29, 95% confidence interval [CI]: [1.98; 5.49], p <0.001) (16).
Schauer et al. performed a randomized controlled trial comparing conservative treatment versus SG or RYGB in patients with poorly controlled type 2 diabetes. Five years after treatment, 45% of patients in the RYGB group were in complete remission (normal HbA1c without antidiabetic medication); the figure in the SG group was only 25% (p <0.05) (17).
There was also a strong consensus among the experts regarding contraindications. Obesity surgery and/or surgery for metabolic indications should not be performed in the following situations:
- If the patient is in an unstable psychopathological state, e.g., untreated bulimia nervosa or ongoing substance dependence
- In the presence of underlying diseases associated with a catabolic state, malignant neoplasms, untreated endocrine disturbances, or other chronic diseases that could be made worse under the catabolic conditions brought about by the operation
- If the patient is pregnant or intends to become pregnant in the near future.
These contraindications are relative, except for pregnancy, and they are not supported by evidence. The decision should be made on the basis of an individualized, interdisciplinary risk–benefit analysis. Decisions against surgery should be re-evaluated if the disease that was considered a contraindication has been successfully treated, or if the contraindicating psychopathological state has been stabilized.
Surgical procedures and results
No procedure can be recommended as a universal standard; the choice of treatment is an individual one, taking due consideration of the initial weight, accompanying diseases if any, the patient’s wishes, etc. Currently established standard techniques include gastric banding (laparoscpic adjustable gastric banding, LAGB), sleeve gastrectomy (SG), proximal Roux-en-Y gastric bypass (RYGB), omega-loop gastric bypass (MGB), and biliopancreatic diversion with or without duodenal switch (Table 1). The evidence profile of the various techniques is presented in Table 2.
The findings of two high-quality meta-analyses regarding the more common procedures are worth examining in detail. Chang et al. carried out a meta-analysis (evidence level 2 ++) using data from 37 RCTs and 127 observational studies, which were derived from a total of 161 756 patients (18). They studied the relative effects of various interventions on Δ BMI (RYGB as reference; 5 years of follow-up), as revealed by 17 RCTs, in a mixed-treatment meta-analysis. Nonsurgical interventions led to the smallest reduction of BMI; 14 (6–22) additional BMI points of weight loss were achievable with RYGB. SG led to similar results. In the RCTs, the rate of remission of pre-existing type 2 diabetes 5 years after surgery was 92% (95% CI: [85; 97]).
Yu et al. (evidence level 2 ++, meta-analysis of 2 RCTs and 24 cohort studies, 2.1–20 years of follow-up) studied the long-term effects of obesity surgery on type 2 diabetes (19). For all procedures combined, the mean weight loss on last follow-up was 50.5% EWL (95% CI: [43.8; 57.2]). The mean BMI reduction after various procedures was: BPD/DS (biliopancreatic diversion with duodenal switch), 18.8 kg/m2 (95% CI: [18.9; 18.7]); RYGB, 12.6 kg/m2 (95% CI: [20,1; 5,1]); AGB (adjustable gastric banding), 11.3 kg/m2 (95% CI: [13.4; 9.2]); sleeve gastrectomy, 10.4 kg/m² (95% CI: [15.0; 5.7]).
The rate of complete remission of pre-existing type 2 diabetes for all procedures combined was 64.7%, and the rate of improvement or remission was 89.2%. The remission rate was highest after BPD/DS (99.2%; 95% CI: [97.0; 99.8]), followed by RYGB (74.4%; 95% CI: [66.9; 80.6]), SG (61.3%; 95% CI: [45.9; 74.8]), and AGB (33.0%; 95% CI: [16.1; 55.8]). Subgroup analyses revealed no statistically significant differences across procedures with respect to either weight loss or diabetes remission.
Long-term data are available, for example, from the SOS study (a prospective interventional study) (20). The mean weight loss among patients who underwent surgery was 18% at 20 years after the procedure. These patients, in comparison to the conservatively managed control group, had lower overall mortality (adjusted hazard ratio [HR] 0.71, 95% CI: [0.54; 0.92]; p = 0.01) and lower rates of myocardial infarction and stroke (adjusted HR 0.71, p = 0.02, and 0.66, p = 0.008, respectively).
The perioperative morbidity and mortality of obesity surgery are relatively low. In the large-scale meta-analysis of Chang et al. (18), the 30-day mortality of surgery in the RCTs was 0.08 % (95% CI: [0.01; 0.24]), which is lower than that of laparoscopic cholecystectomy. The perioperative morbidity in the RCTs was 17% (95% CI: [11; 23]), consisting mainly of minor complications (18). The most common complications of obesity surgery (all of them rare) were staple-line fistula, anastomosis insufficiency, abscess, and bleeding.
Meticulous postoperative care is indispensable and is supported by a strong expert consensus. The evidence regarding the proper extent of postoperative care is not of high quality, but the outcome is clearly better in patients who receive intensive postoperative care and participate in self-help groups (22). The key elements of postoperative care are the following:
- Checking whether the goal of treatment has been reached
- Monitoring comorbidities and changing medications as indicated
- Encouraging the patient to exercise and follow a proper diet
- Early recognition of complications, etc.
There was expert consensus concerning the timing of follow-up examinations and laboratory checks: after surgery for obesity and/or metabolic indications (except gastric banding), follow-up examinations should take place at 1, 3, 6, 12, 18, and 24 months, and then annually. Laboratory values should be checked at 6 and 12 months, and thereafter at intervals depending on the particular surgical procedure and on the patient’s comorbidities. At least the following should be checked:
- Complete blood count, electrolytes, hepatic and renal function tests, blood glucose and HbA1c (only in diabetics), vitamins B1and B12, albumin, calcium, folic acid, ferritin
- After any type of bypass procedure: 25(OH)D3, parathormone, vitamin A
- After distal bypasses: zinc, copper, selenium, magnesium.
Patients with preoperatively recognized mental illness and/or self-injurious behavior should be actively questioned postoperatively about the presence, recurrence, or worsening of their mental problems, and about suicidality.
Successful weight loss may necessitate skin-removal surgery, particularly from the abdomen and the thighs, but sometimes even from the arms and chest. Consultation with a plastic surgeon should be made available to the patient.
Prophylactic dietary supplementation is indicated after any type of surgery for obesity or a metabolic indication. Dosage recommendations for the individual micronutrients are given in Table 3.
Conflict of interest statement
Prof. Dietrich has served as a paid consultant for BOWA and has received reimbursement of meeting participation fees and of travel and accommodation costs from Medtronic, Johnson & Johnson, Bowa, and Novo Nordisc. He has received lecture honoraria from Bauerfeind, Johnson & Johnson, and BOWA.
Dr. Schütz has received reimbursement of meeting participation fees and of travel and accommodation costs from ETHICON and Johnson & Johnson.
Dr. Aberle, Prof. Wirth, Prof. Müller-Stich, and Dr. Tigges state that they have no conflict of interests.
Manuscript submitted on 12 July 2018, revised version accepted on 12 July 2018.
Translated from the original German by Ethan Taub, M.D.
Prof. Dr. med. Arne Dietrich
Klinik für Viszeral-, Transplantation-, Thorax- und Gefässchirurgie
Liebigstr. 20, 04103 Leipzig, Germany
eMethods, eTables and eFigure:
Department of Visceral, Transplantation, Thoracic and Vascular Surgery, University Hospital Leipzig: Prof. Dr. med. Arne Dietrich
III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg: PD Dr. med. Jens Aberle
Bad Rothenfelde: Prof. Dr. med. Alfred Wirth
Department of General, Visceral and Transplantation Surgery, University of Heidelberg:
Prof. Dr. med. Beat Müller-Stich
Department of General, Visceral and Vascular Surgery, Klinikum Landsberg am Lech:
Dr. med. Harald Tigges
* See eTable 1 for a comprehensive list of societies, associations, authors and collaborators involved in the development of the S3 guideline
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