Obesity Surgery

Abstract

Background

In 2017, the prevalence of obesity (BMI ≥= 30 kg/m2) in Germany was approximately 16%. Obesity increases an individual’s risk of developing type 2 diabetes (T2DM) and arterial hypertension; it also increases overall mortality. Consequently, effective treatment is a necessity. Approximately 20 000 bariatric operations are performed in Germany each year.

Methods

This review is based on pertinent publications retrieved by a selective search in the PubMed and Cochrane databases and on current German clinical practice guidelines.

Results

The types of obesity surgery most commonly performed in Germany, Roux-en-Y gastric bypass and sleeve gastrectomy, lead to an excess weight loss of 27–69% ≥= 10 years after the procedure. In obese patients with T2DM, the diabetes remission rate ≥= 10 years after these procedures ranges from 25% to 62%. Adjusted regression analyses of data from large registries have shown that the incidence of malignancies is 33% lower in persons who have undergone obesity surgery compared to control subjects with obesity (unadjusted incidence 5.6 versus 9.0 cases per 1000 person-years). The operation can cause vitamin deficiency, surgical complications, gastroesophageal reflux, and dumping syndrome. Therefore, lifelong follow-up is necessary.

Conclusion

In view of an increasing number of patients undergoing bariatric surgery, it will probably not be feasible in the future for lifelong follow-up to be provided exclusively in specialized centers.

The prevalence of obesity (body-mass index [BMI] ≥ 30kg/m²) has risen in the last 40 years in all countries for which epidemiologic data are available (1). In Germany, 16.3% of the population was obese in 2017 (e1). Obesity has a clear effect on overall mortality, which rises by 29% with every 5 kg/m² increase in BMI (hazard ratio [HR]: 1.29; 95% confidence interval: [1.27; 1.32]). The life expectancy of persons with a BMI in the range of 40–45 kg/m² is reduced by eight to ten years. This effect is comparable to that of cigarette smoking (2). 25.6% of persons with BMI ≥ 40 kg/m² suffer from type 2 diabetes (T2DM), and 50.9% from arterial hypertension. This corresponds to a 7.4-fold increase of the risk of T2DM and a 6.4-fold increase of the risk of arterial hypertension compared to persons of normal weight (e2). Among persons with BMI ≥ 30 kg/m², 14.9% have T2DM and 40.9% have arterial hypertension (e2). In western Europe, 3.3% [3.0; 3.6] of all cancers in men and 7.8% [7.1; 8.5] of all cancers in women can be attributed to obesity (3). Table 1 contains a description of five tumor entities for which a strong epidemiologic association with obesity has been shown in a global meta-analysis (4). 13% of the overall healthcare costs of obesity associated diseases (such as T2DM) in Germany, amounting to 5.2 billion euros per year, are attributable to obesity (e3). These data highlight the urgency of effective treatment and improved secondary prevention.

Table 1. Cancer risk in obese persons and reduction of the risk of selected types of cancer after obesity surgery.

Type of cancer	Relative risk in obese persons (BMI ≥ 30 kg/m2) [95% KI] compared to persons of normal weight	Risk of the type of cancer in question after obesity surgery [95% CI]
Colon cancer	1.47 [1.35; 1.60] (e45)	relative risk compared to obese controls BMI ≥ 30 kg/m2: 0.64 [0.42; 0.98] (35)
Rena-cell carcinoma	1.76 [1.61; 1.91] (e46)	hazard ratio compared to matched obese controls BMI ≥ 35 kg/m2: 0.79 [0.51; 1.24] (27)
Hepatocellular carcinoma	1.90 [1.61; 2.24] (e47)	odds ratio compared to obese controls BMI ≥ 30 kg/m2: 0.63 [0.53; 0.75] (e48)
Endometrial carcinoma	2.54 [2.27; 2.81] (e49)	relative risk compared to obese controls BMI ≥ 30 kg/m2: 0.33 [0.21; 0.51] (e50)
Esophageal adenocarcinoma	2.73 [2.16; 3.46] (e51)	hazard ratio compared to obese controls BMI ≥ 30 kg/m2: 0.9 [0.4; 1.9] (e52)

BMI, body-mass index, CI, confidence interval.

Prevalence.

In Germany, 16.3% of the population was obese in 2017. Obesity has a clear effect on overall mortality.

Comorbidities.

25.6% of persons with BMI ≥ 40 kg/m2 suffer from type 2 diabetes mellitus (T2DM), and 50.9% from arterial hypertension. This corresponds to a 7.4-fold increase of the risk of T2DM and a 6.4-fold increase of the risk of arterial hypertension compared to persons of normal weight.

Obesity surgery, with appropriate preoperative care and lifelong follow-up, leads to sustained weight loss (45.9–80.9% loss of excess body weight [EWL] at 10–25 years) (e4) as well as to improvement of pre-existing T2DM (5). Moreover, in a meta-analysis of data from 174 772 persons, mortality in the 30 years after obesity surgery was found to be 49.2% [46.3; 51.9] lower than in control patients with obesity (with or without any other specific treatment), with a life expectancy that was 6.1 [5.2; 6.9] years longer (6).

In this CME article, we present the indications, basic principles, and results of obesity surgery. Moreover, typical long-term effects of surgery are discussed, and specific aspects of follow-up care are described, including vitamin supplementation.

Learning objectives

Readers of this article should achieve the following learning objectives:

• an understanding of the mechanism of action of obesity surgery and a knowledge of its indications;

• acquaintance with the key results of obesity surgery;

• the ability to recognize reflux and dumping syndrome as clinically relevant long-term consequences of obesity surgery.

Methods

The effects of obesity surgery.

Obesity surgery, with appropriate preoperative care and lifelong follow-up care, leads to sustained weight loss (45.9–80.9% loss of excess body weight at 10–25 years), as well as to improvement of pre-existing T2DM.

This article is based on a selective literature review in the PubMed and Cochrane databases for the years 2003–2021, with the following searching terms: bariatric surgery AND type 2 diabetes; vitamin supplementation; dumping syndrome; complication; cancer; oncology. Further searching terms were endoscopy AND dumping syndrome, as well as obesity AND disease risk; cancer. The contents of the current German clinical practice guidelines were considered as well (7, 8).

Baseline treatment for patients desiring obesity surgery

Patients with a potential indication for obesity surgery should be offered preparatory and accompanying conservative treatment options (7). These should include a combination of dietary counseling, exercise, and behavioral therapy and should contain individualized nutritional recommendations. The treatment goal is the loss of at least 10% of initial weight within 6 to 12 months in a patient whose BMI exceeds 35 kg/m² (7). The data show that efficient, high-intensity interval training combined with dietary counseling in patients with a BMI of 40.4 ± 7.2 kg/m² resulted in 5.3 [3.3; 7.3] kg of weight loss at 12 weeks and in a significant improvement of cardiovascular risk factors (abdominal girth -7.5 cm [–9.8; –5.1 cm], mean blood pressure -11 mm Hg [–14; –8 mm Hg]) (e5).

Baseline treatment for patients desiring obesity surgery.

Patients with a potential indication for obesity surgery should be offered preparatory and accompanying conservative treatment options.

Long-term results were investigated in a meta-analysis of 91 studies on patients with obesity (BMI >30 kg/m²) treated with combined nutritional and behavioral therapy. In the subgroup analysis of patients with grade II and III obesity, the overall weight loss at six to 24 months was 5.3% and 6.3%, respectively (9). Accordingly, the German clinical practice guideline summarizes that treatment goals for obesity are “generally not achieved” by conservative treatment (7).

Conservative treatment has thus taken its place as a component of the interdisciplinary preparatory phase and the postoperative care of patients with a BMI ≥ 35 kg/m² who desire obesity surgery. Baseline treatment need not necessarily be followed by obesity surgery. The efficacy of this strategy has been shown in a meta-analysis of studies on targeted interventions including nutritional counseling, behavioral therapy, and exercise in the 12 months before and after obesity surgery. 12 months after surgery, the patients so treated had lost 4.4 kg [1.69; 7.1] more than the control patients who had undergone obesity surgery without any other targeted intervention (e6).

Results of accompanying treatment.

The data show that efficient, high-intensity interval training combined with dietary counseling in patⁱents with a BMI of 40.4 ± 7.2 kg/m2 resulted in 5.3 [3.3; 7.3] kg of weight loss at 12 weeks and in a significant improvement of cardiovascular risk factors, including mean blood pressure.

The surgical treatment of obesity

The indication criteria for obesity surgery are listed in the Box. The patient’s body weight remains the main criterion on which the indication for obesity surgery is based, even though the goals of obesity surgery now extend well beyond weight loss alone (10).

BOX. Indications for obesity and metabolic surgery.

Indications for obesity surgery

• after the exhaustion of conservative treatment modalities

  • BMI ≥ 35 and < 40 kg/m² with obesity-associated comorbidities*

  • BMI ≥ 40 kg/m²

• primary indication

  • BMI ≥ 50 kg/m²

  • if conservative treatment does not promise to be successful

  • if the comorbidities are particularly severe

Indications based on metabolic parameters in patients with type 2 diabetes

• if BMI ≥ 40 kg/m², surgery is indicated independently of glycemic control

• if BMI ≥ 35 and < 40 kg/m², surgery is indicated if diabetes-specific target values can not be achieved

• if BMI ≥ 30 and < 35 kg/m², metabolic surgery is an option if diabetes-specific target values can otherwise not be reached

Overview of indications for obesity surgery and metabolic surgery according to the German clinical practice guideline on the surgical treatment of obesity and metabolic diseases (7).

Conservative treatment is considered to be exhausted when at least six months of comprehensive lifestyle interventions in the last two years have not resulted in the loss of at least 15% of the initial weight in a patient with a BMI in the range of 35–39,9 kg/m², or of at least 20% of the initial weight in a patients with a BMI above 40 kg/m² (7).

* The following are defined to be obesity-associated comorbidities: Type 2 diabetes (T2DM), coronary artery disease, heart failure, hyperlipidemia, arterial hypertension, nephropathy, obstructive sleep apnea syndrome (OSAS), obesity-hypoventilation syndrome, Pickwick syndrome, nonalcoholic fatty liver disease (NAFLD) or nonalcoholic steatohepatitis (NASH), pseudotumor cerebri, gastroesophageal reflux disease (GERD), asthma, chronic venous insufficiency, urinary incontinence, immobilizing joint disease, impaired fertility, polycystic ovary syndrome (PCO).

BMI, body-mass index

Metabolic surgery is indicated in patients with grade II obesity (BMI ≥ 35 to < 40 kg/m²) and T2DM whenever the treatment goals for T2DM as stated in the guidelines cannot be achieved with conservative therapy alone. For patients with T2DM and grade III obesity (BMI >40kg/m²), surgery is indicated independently of glycemic control, as long as potential contraindications have been excluded (box) (7). As with the primary indication, the documented inefficacy of conservative obesity therapy is not required (7). Data on diabetes remission at least five years after Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) reveal that particularly patients with a short history of type 2 diabetes, no insulin use, a treatment regimen with a small number of antidiabetic drugs, and good glycemic control (HbA1c <7%) under conservative treatment stand to benefit from metabolic surgery (11). Moreover, diabetes remission after metabolic surgery is independent of the initial BMI, as shown by a meta-analysis of data from 94 579 patients (12). These findings may prompt a reappraisal of the indications for metabolic surgery in the near future.

The contraindications for obesity surgery and metabolic surgery are clearly presented in the German clinical practice guideline. These include untreated bulimia nervosa, active substance dependence, or untreated endocrine causes of obesity (7).

Mechanisms of action of obesity surgery

Indication: body weight.

The patient’s body weight remains the main criterion on which the indication for surgery is based, even though the goals of obesity surgery now extend well beyond weight loss alone.

The main objective of obesity surgery is to restrict energy intake. This is done by surgically decreasing the stomach volume, so that only small portions of food can be consumed. The surgical procedures often involve gastric reduction combined with bypassing the duodenum and part of the jejunum (Figure). The ones most commonly performed in Germany, SG and RYGB, do not cause any clinically relevant malabsorption of macronutrients (e7). The contribution of malabsorption to weight loss after RYGB has been estimated at 11% in a systematic review (e8). Though they differ in their anatomical details, the various obesity surgery procedures all cause complex intestinal hormonal changes, including increased levels of glucagon-like peptide 1 (GLP-1) and circulating bile acids, as well as lower ghrelin levels; clinically, patients have a reduced appetite, decreased neural stimulability, and lessened food reward compared to their preoperative state (e9). The hormonal changes after surgery are partly opposite to those induced by conservative treatment, which can raise ghrelin and cholecystokinin levels and increase the appetite (e10). If the described entero-endocrine regulation did not occur after obesity surgery, the ensuing sustained weight loss would be unexplained, because dilation of the stomach over the long term would again permit the consumption of large portions of food (e11). The most common surgical procedures are depicted in the Figure.

Figure:

Surgical procedures in obesity and metabolic surgery (Dr. Leven Efe, courtesy of the International Federation for the Surgery of Obesity and Metabolic Disorders [IFSO]). (e44)

a) Sleeve gastrectomy (SG) with the removal of 80–90% of the stomach along an inserted calibration tube (diameter 1.2–1.5 cm). The resected stomach part is removed. Sleeve Gastrectomy is the most commonly performed type of obesity surgery in Germany (approximately 50% of operations for obesity).

b) Roux-en-Y gastric bypass (RYGB): A small, elongated gastric pouch (20–30 mL) is created and directly connected to the small intestine via Roux-en-Y reconstruction. The lengths of the resulting biliopancreatic (green) and alimentary (yellow) limbs are variable; typically, the alimentary limb is 150 cm long, and the biliopancreatic limb 50 cm long. This results in hypoabsorption, but not malabsorption. Gastric bypass is the second most common type of obesity surgery in Germany (circa 32% of all procedures for obesity). It is surgically reversible, as it does not involve the resection of any part of the bowel or stomach.

c) One-anastomosis gastric bypass (OAGB): a gastric pouch is formed that is similar to the one made in RYGB, but slightly longer. The small intestine is then anastomosed to the stomach as an omega loop. The biliopancreatic (green) limb is typically 150–250 cm long, although numerous variations have been described. OAGB accounts for approximately 15% of the surgical procedures for obesity that are performed in Germany.

d) Gastric banding (LAGB): The gastric band is placed just below the gastroesophageal junction and connected to a subcutaneously implanted port. With this port, the degree of filling of the inner cushion of the gastric band, and thus the inner diameter of the band, can be regulated from the outside. Because of its many complications, and its lesser effect on weight than other types of obesity surgery, gastric banding is now only used in special situations (ca. 1% of procedures in Germany).

e) Duodenal switch (BPD-DS): In this operation, sleeve gastrectomy is combined with duodenum division distal to the pylorus. Reconstruction of the passage is basically analogous to RYGB, although the loop lengths are markedly different: the alimentary limb is approx. 250 cm long, and the common distal segment (common channel) is 75–100 cm long. The biliopancreatic loop, which is usually not measured, is several meters long. Because the common channel is so short, the duodenal switch leads to marked hypoabsorption, in turn necessitating parenteral vitamin supplementation and leading to frequent, mushy stools. Few procedures of this type are performed in Germany (about 0.5% of all operations).

Weight loss

A meta-analysis of eleven randomized controlled trials (RCTs) revealed that obesity surgery leads to a mean amount of weight loss at two years that is 26 kg [31; 21 kg] greater than that resulting from conservative treatment alone (-38.5 to -14.4 kg, versus -7.9 to +1.0 kg) (13). The only Cochrane review to date on weight loss after obesity surgery revealed a similar difference of 21.3 kg [18.9; 23.6 kg] at 12–24 months (14). Long-term data from one of the included studies have become available in the meantime and show a large sustained difference in weight loss between RYGB and conservative treatment at 10 years (RYGB, -37.3 kg; conservative treatment, -6.5 kg; difference, 30.8 kg [16.7; 44.8 kg]) (15). In the prospective Swedish Obese Subjects (SOS) cohort trial, which involved 4047 patients, the overall weight loss at 15 years was 27% after RYGB, versus 0% in the control patients (some of whom received no specific treatment for obesity) (16).

Table 2 contains a detailed overview of weight loss after different obesity surgery procedures. It has been found in multiple RCTs that the two most common surgical procedures, SG and RYGB, lead to similar degrees of weight loss (14). Pooled data from the two largest randomized trials of SG versus RYGB, both of them published in 2021, imply that RYGB leads to significantly more weight loss at five years (EWL 67.7% versus 55.5%) (17). An advantage for RYGB over SG has likewise been found in three more recent meta-analyses, as well as in one RCT with 7-year follow-up data (18, 19, e12, e13). These newer findings remain to be confirmed.

Table 2. The outcomes of obesity surgery and metabolic surgery.

Type of procedure	Loss of excess weight (EWL)			Type 2 diabetes				30-day mortality
	1–2 years	5–7 years	≥ 10 years	Remission 2–3 years	Remission 5 years	Partial remission 5 years	Remission ≥ 10 years
LSG	51–79% (36)	54–57% (e53, 18)	53–62% (e4)	50–67% (24, 21)	28–59% (18, e53)	74% (18)	58% (e54)	0.03–0.33% (e55, e56)
RYGB	63–72% (36)	66–72% (18, e53)	27–69% (e4)	75% (37)	37–76% (18, e53)	77.5% (38)	25–62% (15, e54)	0.07% (e55, e56)
OAGB	31–89% (20)	30–73% (20)	70–84% (e4)	60% (e14)	67–94% (e53, e57)	85% (e58)	67% (e57)	0–0.26% (e53, e56)
BPD-DS/BPD	73% (e59)	75% (e59)	61–94% (e4)	98% (39)	88–99% (38)	63% (39)	50–68% (15, e60)	0.6–0.8% (38)
LAGB	33–34% (36)	42–57% (36)	27–66% (e4)	20% (e61)	16% (e61)	23% (e61)	18% (e62)	0–0.1% (40, 36)

Weight loss is presented as loss of excess body weight (EWL), and the results with regard to type 2 diabetes are presented for each surgical technique as described in the pertinent references. BPD-DS/ BPD: biliopancreatic diversion with duodenal switch and biliopancreatic diversion are presented together; LAGB, gastric banding; LSG, sleeve gastrectomy; RYGB, Roux-en-Y gastric bypass; OAGB, one-anastomosis gastric bypass.

Contraindications of obesity surgery and metabolic surgery.

These include untreated bulimia nervosa, active substance dependence, or untreated endocrine causes of obesity

A meta-analysis of data from 12 445 patients revealed that weight loss one, two, and five years after one-anastomosis gastric bypass (OAGB) was greater than after RYGB: the difference in EWL at five years was 12.82% [5.37; 20.27%] (20). A disadvantage of OAGB compared to RYGB is a higher rate of malnutritive complications (21% versus 0%), as shown in one randomized controlled trial (e14).

Clinically relevant weight regain (defined as an increase of at least 25% from the nadir) occurs in approximately 20% of patients at a median follow-up of five years and is apparently higher after SG than after RYGB (e15). In such cases, a reoperation may be indicated. In order to minimize weight regain, silicone rings can be implanted around the stomach during the primary procedure. Weight regain three to five years after RYGB or SG has been found to be significantly less if silicone rings are used (21, e16).

The course of diabetes after obesity surgery

Effects of hormonal changes.

Hormonal changes after obesity surgery include reduced appetite, decreased neural stimulability, and lessened food reward compared to the patients’ preoperative state

In a meta-analysis of data from 1108 patients, metabolic surgery brought about a remission of preexisting T2DM in 59.3% (RYGB) to 91.2% (OAGB) of patients at five years (5). The only RCT to date with 10 years of follow-up revealed a diabetes remission rate of 37.5% after metabolic surgery and 0% after medical management alone. In this trial, the percentage of patients needing insulin rose from 47% to 53.3% in the medical group and fell from 47.5% to 2.5% in the surgical group. The incidence of macrovascular and microvascular complications of T2DM at 10 years was 5.0% in the surgical group and 72.2% in the medical group (relative risk 0.07 [0.01; 0.48] (15). Likewise, a meta-analysis of data from 17 532 patients with T2DM who were treated either medically or surgically revealed lower incidences of diabetic retinopathy (1.9% versus 6.6%; odds ratio [OR] 0.30) and nephropathy (5.9% versus 22.4%; OR 0.19) in the surgical group at 1–15 years (e17). The incidence of diabetes in the prospective SOS cohort at 15 years was 6.8 per 1000 person-years after obesity surgery and 28.4 per 1000 person-years in the control group, corresponding to a relative risk reduction of 78% (22).

Multiple meta-analyses have shown statistically similar antidiabetic effects for SG and RYGB at five years (table 2) (23, 24). In contrast, in a cohort study from the USA including 9710 patients with SG or RYGB at 34 centers, RYGB resulted in better glycemic control (ΔHbA1c 0.45; [0.27; 0.63]), a 10% higher diabetes remission rate (HR 1.1 [1.04; 1.16], and a lower diabetes recurrence rate (HR 0.75 [0.67; 0.84] than SG (25). In a study of 629 patients followed up for a median of 4.9 years after RYGB, independent predictive factors for diabetes recurrence were the preoperative insulin requirement, lower weight loss at 12 months, and greater regaining of weight after the first year (26).

Weight gain.

Clinically relevant regaining of weight (defined as an increase of at least 25% from the nadir) occurs in approximately 20% of patients at a median follow-up of five years and is apparently higher after SG than after RYGB.

Cancer prevention

A retrospective observational study of 22 198 patients who underwent obesity surgery, compared to 66 427 controls who were closely matched for sex, age, BMI, and comorbidities, determined that the incidence of cancer in 3.5 years of follow-up was 5.6 per 1000 person-years in the surgical group, compared to 9.0 per 1000 person-years in the nonsurgical group, which corresponded to a 33% relative reduction (27). With regard to individual types of cancer, a meta-analysis of data from more than 7 million patients revealed that endometrial cancer arose within four to 26 years in 0.4% of women who underwent obesity surgery, compared to 0.6% of women in the control group. This meta-analysis showed a 59% (OR 0.41 [0.22; 0.74]) lower risk of endometrial cancer after obesity surgery (e18). As for colorectal cancer (CC), a population-based, multicenter study from France involving 1.05 million persons with obesity followed up for at least 2 years revealed an absolute CC incidence of 0.6% within 10 years after obesity surgery compared to 1.3% in the control group. The risk of CC after obesity surgery was the same as in the normal population (standard incidence ratio [SIR] 1.0; [0.9; 1.09]), but it was 34% higher (SIR 1.34; [1.32; 1.36]) in obese persons who did not undergo obesity surgery (28).

Follow-up

Patients who have undergone obesity surgery benefit from regular follow-ups. In support of this assertion, a register based study including 46 381 patients 12 months after RYGB showed that those who adhered to scheduled postsurgical follow-ups had better remission rates of T2DM (OR 1.27; [1.18; 1.37]) and arterial hypertension (OR 1.25; [1.18; 1.32]), after adjustment for age, sex, BMI, and other factors (e19). In Germany, approximately 20 000 surgical procedures for obesity are performed per year (e20). The rapidly rising numbers of patients and operations will soon make it impossible for lifelong follow-up to be provided in specialized centers alone (29). In the next section, we outline what appropriate follow-up consists of and discuss two potential long-term sequelae, i.e., reflux and dumping syndrome. The necessary laboratory tests and supplementation recommendations are listed in Table 3.

Table 3. Prevalences of micronutrient deficiency, laboratory tests, recommendations on vitamin supplementation following obesity surgery, and recommended vitamin and micronutrient intake according to the German Nutrition Society (Deutsche Gesellschaft für Ernährung) (e63).

Micro-nutrient	Prevalence of micronutrient deficiency	Symptoms of micronutrient deficiency	Recommended follow-up intervals after obesity surgery	Recommended quantity of supplementation	Recommended intake according to DGE
Vitamin A
LSG	5.2%	nyctalopia, Bitot spots, hyperkeratinization of the skin	–	1500 RAE*2	M: 850 RAEF: 700 RAE
RYGB	7.7%		at 3, 6, and 12 months, then annually	1500–3000 RAE*2
Thiamine (vitamin B1)
LSG	prevalence depending on risk factors such as vomiting, alcohol abuse < 1–49 %.	dry beriberi involving the nervous system, wet beriberi with heart failure and edema; Wernicke’s encephalopathy.	at 6 and 12 months, then annually	12 mg/day*2	M: 1.2 mg/dayF: 1.0 mg/day
RYGB			at 3, 6, and 12 months, then annually
Calcium
LSG	not applicable; see prevalence of vitamin D deficiency.	leg cramps, muscle weakness, osteoporosis	at 6 and 12 months, then annually	1200–1500 mg/day of calcium citrate	M: 1000 mg/dayF: 1000 mg/day
RYGB			at 3, 6, and 12 months, then annually
Vitamin D
LSG	very high prevalence (up to 100% in some collectives)	leg cramps, paresthesiae, hypocalcemia, osteoporosis	at 6 and 12 months, then annually	at least 3000 IE/day, target serum concentration > 30 mg/mL	M: 800 IE/dayF: 800 IE/day
RYGB			at 3, 6, and 12 months, then annually
Iron			Ferritin
LSG	< 18%	fatigue, prostration, microcytic anemia, susceptibility to infections, glossitis, koilonychia	at 6 and 12 months, then annually	50*2 mg/day in women of childbearing age	M: 10 mg/dayF: 15 mg/day
RYGB	20–55%		at 3, 6, and 12 months, then annually	50 mg/d of iron sulfate, fumarate, gluconate
Folic acid (Vitamin B9)
LSG	up to 65% described	megaloblastic anemia, neural tube defects (embryo)	at 6 and 12 months, then annually	600*2 µg/day	M: 300 µg/dayF: 300 µg/day
RYGB			at 3, 6, and 12 months, then annually	600 µg/day
Vitamin B12
LSG	4–20%	pernicious (megaloblastic) anemia, skin pallor, glossitis, fatigue, numbness/paresthesiae, ataxia, tinnitus	at 6 and 12 months, then annually	oral: 1000 µg/dayi.m.: 1000–3000 µg every 3–6 months	M: 4 µg/dayF: 4 µg/day
RYGB	< 20%		at 3, 6, and 12 months, then annually
Vitamins E and K
LSG	low prevalence	vitamin E: hyporeflexia, gait disturbance, ophthalmoplegia vitamin K: bleeding tendency	–	vitamin E: 15*2 mg/day vitamin K: 90–120*2 µg/day	vitamin E: M: 14 mg/day F: 12 mg/day vitamin K: M: 70 µg/day F: 60 µg/day
RYGB			at 3, 6, and 12 months, then annually (no recommendation from the ASMBS)
Zinc
LSG	19%	rash, acne, hypogeusia, susceptibility to infections, infertility	–	8–11*2 mg/day	M: 14 mg/dayF: 8 mg/day
RYGB	40%		at 3, 6, and 12 months, then annually
Copper
LSG	Low prevalence	hypochromic anemia, neutropenia, hypopigmentation	–	1*2 mg/day	M: 1–1.5 mg/dayF: 1–1.5 mg/day
RYGB	10–20 %		annually*1	2 mg/day

Figures on the prevalence of micronutrient deficiency are taken from the ASMBS guideline (e64). For vitamin A, Parrot et al. (e64) did not specify prevalence and the figures are taken from Johnson et al. (e65). The recommended laboratory tests are as per the German clinical practice guideline (7); *¹ not recommended in the German clinical practice guideline, but recommended by the ASMBS. The ASMBS does not recommend laboratory testing for patients who have undergone RYGB because of the low prevalence of vitamin E and vitamin K deficiency. The recommended supplementation amounts are also taken from the German clinical practice guideline and are complemented by the ASMBS recommendations when the amount to be substituted is not specified (marked by *²). All supplementation amounts listed in bold are typically contained in specially formulated multivitamin tablets for patients who have undergone obesity surgery. ASMBS, American Society for Metabolic and Bariatric Surgery; DGE, German Society for Nutrition; F, female; i.m., intramuscular; LSG, sleeve gastrectomy; M, male; RAE, retinol activity equivalent; RYGB, Roux-en-Y gastric bypass.

Specific aspects of follow-up

The course of diabetes after obesity surgery.

In a meta-analysis of data from 1108 patients, metabolic surgery brought about a remission of preexisting T2DM in 59.3% (RYGB) to 91.2% (OAGB) of patients at five years.

In a large-scale meta-analysis, obesity surgery led to the remission of preexisting arterial hypertension in 24 902 (50%) of 49 844 patients (e21). This implies that the antihypertensive medication must be continually readjusted. The same applies to T2DM: insulin secretagogues should be stopped, and the subcutaneous insulin dose should be adjusted (30). The use of sodium-glucose cotransporter 2 (SGLT2) inhibitors is not recommended for six to twelve months after obesity surgery because of the increased risk of ketoacidosis (7). A meta-analysis on the effect of exercise after obesity surgery revealed that participation in an exercise program was associated with a slightly greater degree of weight loss (–1.8 kg [–3.2; –0.4]) and improved physical performance (VO₂max and muscle strength) (e22).

It is recommended in the German clinical practice guideline that self-injurious behavior should be directly asked about if the patient has a relevant preoperative disturbance, and that the history of self-injurious behavior should be appropriately documented (7). A meta-analysis of 29 studies revealed a suicide rate of 2.7 per 1000 patients after obesity surgery. The risk of suicide after obesity surgery was 1.9 times higher [1.23; 2.95] than in the same population preoperatively, and 3.8 times higher than in matched controls [2.91; 6.59] (e23). A comparison of the SOS cohort with persons in two Swedish national registries showed that the additional risk was much higher in men than in women. Moreover, it was found that a history of psychological consultations, psychotropic drug use, and sleep disturbances are risk factors for suicide after obesity surgery (e24). A systematic review of 48 studies on depression, anxiety disorder, and binge eating indicated that these disorders may improve 6–24 months after obesity surgery; some of the included studies showed, however, that these disorders may return to baseline levels beyond 24 months after surgery (31). In light of these findings a psycholocical follow up is desirable, especially for patients at risk.

Data show that 4.6% of patients develop anastomotic ulcers after RYGB. Nonsteroidal anti-inflammatory drugs (NSAID, OR 30.6 [6.4; 146]) and smoking (OR 11.5 [4.8; 28]) markedly increase this risk (e25). Proton-pump inhibitors are protective and are thus recommended for ulcer prophylaxis for one to six months after gastric bypass (7). Short-term NSAID use is, however, possible even after RYGB (30). A meta-analysis of 10 031 patients revealed a 2% incidence of internal hernias after RYGB, despite the initial closure of the mesenteric defects (e26). Because of the risk of incarceration, such hernias should be treated surgically (e27).

Follow-up.

In Germany, approximately 20 000 surgical procedures for obesity are performed per year. The rapidly rising numbers of patients and operations will soon make it impossible for lifelong follow-up care to be provided in specialized centers alone.

Reflux

According to a meta-analysis of data from 460 984 patients, obesity (BMI ≥ 30 kg/m²) is associated with a 1.7-fold [1.46; 2.06] higher prevalence of gastroesophageal reflux disease (GERD; absolute prevalence, 22.1% versus 14.2%), (e28). For patients with reflux who have an indication for obesity surgery, gastric bypass is an optimal operative technique, as it creates an anatomical barrier to reflux by bypassing a large portion of the stomach. SG is a poorer choice for this group of patients (7), as it is associated with de novo reflux symptoms in 20% [14; 27], an overall increase in reflux symptoms in 19% [15; 22], and a 28% rate of reflux esophagitis [–9; 66] in the first two years after surgery (32). A meta-analysis of 680 patients who underwent SG accordingly showed an 11.5% [7.8; 16.7] prevalence of Barrett’s mucosa in three years of follow-up (e29). Although no clear temporal relationship was seen between surgery and the onset of Barrett’s metaplasia, the prevalence of reflux esophagitis was found to increase by 13% per year after SG (e29). As there is no correlation between endoscopic findings and reflux symptoms in more than half of cases, the American Society for Metabolic and Bariatric Surgery recommends endoscopic follow-up of all patients three years after SG, and potentially at five-year intervals thereafter, as long as the findings remain unremarkable (e30). Reflux after SG is often a consequence of scarring or functional sleeve stenosis, both of which can relatively impede gastric outflow. Furthermore, axial hiatal hernias with intrathoracic migration of part of the sleeve have been described, inevitably leading to esophageal shortening and partial dysfunction of the lower esophageal sphincter (e31, 33). As causes of reflux after SG are prevalently anatomical in nature, conservative treatment is often ineffective; the most effective and most common treatment is conversion of the sleeve to a RYGB. In a published series of 10 cases, this also led to the remission of Barrett’s esophagus 80% of the time, after a median follow-up of 33.4 months (e32). Other options include hiatoplasty, possibly combined with augmentation using the round ligament of the liver, or the implantation of a magnetic ring (e33).

Reflux.

According to a meta-analysis of data from 460 984 patients, obesity (BMI ≥ 30 kg/m2) is associated with a 1.7-fold [1.46; 2.06] higher prevalence of gastroesophageal reflux disease.

Patients who have undergone OAGB may develop both acid and biliary reflux because of retrograde flow of bile into the gastric pouch in the absence of a Roux anastomosis (e34). The logical management of clinically relevant biliary reflux would be the conversion of the OAGB to a RYGB.

Dumping

The prevalence of dumping syndromes after RYGB is 20–40% (e35). There are two types of dumping syndrome. Type 1 dumping (early dumping, less than one hour after food intake) is caused by rapid transport of hyperosmolar chyme into the small intestine, leading to an influx of interstitial fluid into the intestinal lumen. The mechanism of type 2 dumping (late dumping, one to three hours after food intake) is much less well understood; it is probably due to excessive GLP-1 secretion in response to the rapid transport of glucose into the small intestine (e36), which results in disproportionate insulin secretion and ensuing hypoglycemia. The main symptoms of both types of dumping are dizziness, sweating, tachycardia, and hypotension. They often occur in combination, as both are triggered by the rapid passage of food into the small intestine. Specific therapeutic measures are directed against this rapid passage. The mainstay of treatment is nutritional therapy, with the goal of getting the patient to ingest multiple, small portions of food that are low in carbohydrates, instead of a single large portion. Dumping syndrome can be effectively treated endoscopically by narrowing the gastroenterostomy (e37, e38); open surgical reduction of the gastric pouch and implantation of a silicone ring also markedly improves symptoms, although only limited confirmatory data are available to date (e39). The drugs used to treat dumping syndrome slow glucose uptake (acarbose) and gastrointestinal motility (somatostatin analogues, GLP-1 agonists), or else inhibit insulin secretion (diazoxide, somatostatin analogues) (e40). The treatment that would theoretically seem most effective, i.e., reversal of the gastric bypass, often fails to relieve the symptoms completely (e40).

Perspectives

Pharmacotherapy of dumping syndrome.

The drugs used to treat dumping syndrome slow glucose uptake (acarbose) and gastrointestinal motility (somatostatin analogues, GLP-1 agonists), or else inhibit insulin secretion (diazoxide, somatostatin analogues).

As recommended in the German clinical practice guideline, patients should be followed up 1, 3, 6, 12, 18, and 24 months after obesity surgery, and annually thereafter (7). The appropriate follow-up is most likely to be delivered under real-world conditions if it is comprehensively reimbursed by health insurance carriers. Yet, in Germany at present, full reimbursement is only possible for standard care. The situation is likely to improve markedly in the near future with the adoption of a proposed law mandating the creation of a disease management program for obesity. One result of this may be the reimbursement of pharmacotherapy directed at weight loss, which is currently excluded under §34 of the German Social Code, Book V. This would be of particular benefit to patients with grade I obesity (BMI ≥ 30–35 kg/m²), a group that suffers from increased mortality, yet often cannot achieve sustained weight loss: these patients generally are not candidates for bariatric surgery, and conservative treatment often has no more than a modest effect (34, e41). Moreover, the adjuvant use of weight-reducing drugs after obesity surgery will be increasingly important as better and more comprehensive data are acquired (e42, e43).

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CME credit for this unit can be obtained via cme.aerzteblatt.de until 3 February 2023. Only one answer is possible per question. Please select the answer that is most appropriate.

Question 1

How high is the reported risk of developing colorectal cancer after obesity surgery, in comparison to the corresponding risk in the general population?

1. Twice as high

2. Three times as high

3. 34% higher

4. Only half as high

5. The same

Question 2

What is the most likely mechanism of the long-term weight-reducing effect of gastric bypass and sleeve gastrectomy?

1. Severe protein malabsorption

2. Altered intestinal hormone stimulation and secretion

3. Increased epinephrine secretion

4. Primarily mechanical restriction

5. Shortened colon transit time

Question 3

In general, in what situation is a surgical procedure indicated on the basis of metabolic parameters?

1. Only when conservative treatment has been found to be insufficient

2. If the patient has arterial hypertension and BMI ≥ 40 kg/m²

3. If the patient has lymphedema and BMI ≥ 40 kg/m²

4. If the patient has type 2 diabetes and BMI ≥ 40 kg/m²

5. If the patient has pulmonary arterial hypertension and BMI ≥ 35 kg/m²

Question 4

What surgical technique should be chosen for patients who suffer from gastroesophageal reflux and, at the same time, are concerned about the possibility of bilious reflux?

1. Roux-en-Y gastric bypass

2. Gastric banding

3. Duodenal switch

4. Sleeve gastrectomy

5. One-anastomosis gastric bypass

Question 5

In a relevant randomized and controlled trial with 10 years of clinical follow-up, what was the remission rate of type 2 diabetes after obesity surgery?

1. 17.5%

2. 22.5%

3. 27.5%

4. 32.5%

5. 37.5%

Question 6

In a relevant observational study, to what extent was the incidence of obesity-related types of cancer lowered after obesity surgery?

1. by approximately 70% at 7 years

2. by approximately 30% at 5.5 years

3. by approximately 70% at 3 years

4. by approximately 30% at 3.5 years

5. by approximately 50% at 5 years

Question 7

What is the most commonly performed surgical procedure for obesity in Germany?

1. Gastric banding

2. Roux-en-Y gastric bypass

3. Duodenal switch

4. One-anastomosis gastric bypass

5. Sleeve gastrectomy

Question 8

What factors elevate the risk of an anastomotic ulcer after Roux-en-Y gastric bypass surgery?

1. A diet rich in bran combined with laxative use

2. Moderate consumption of alcohol and red meat

3. Regular use of nonsteroidal anti-inflammatory drugs and smoking

4. Aerobic training and regular use of proton pump inhibitors

5. A low-carbohydrate diet and intermittent fasting

Question 9

What vitamin or trace element deficiency most commonly arises after a sleeve gastrectomy?

1. Vitamin C deficiency

2. Vitamin K deficiency

3. Vitamin E deficiency

4. Copper deficiency

5. Vitamin D deficiency

Question 10

Which of the following would be appropriate management of a patient with severe dumping symptoms after Roux-en-Y gastric bypass who has already obtained no relief from nutritional therapy or from acarbose?

1. Wait and observe further.

2. Treat postprandial tachycardia with a ß-blocker.

3. Perform surgical distalization of the intestinal loops.

4. Perform surgical reduction of the gastric pouch, combined with silicon implantation.

5. Prescribe antacids to be taken with meals.

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