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208 Current Diabetes Reviews, 2014, 10, 208-214

Bariatric Surgery - Effects on Obesity and Related co-Morbidities

Maria Saur Svane* and Sten Madsbad

Hvidovre Hospital, Dept. of Endocrinology, Kettegrd Alle 30, 2650 Hvidovre, Denmark

Abstract: Laparoscopic adjustable gastric banding (LAGB), laparoscopic Roux-en-Y gastric bypass (RYGB) and laparo-

scopic sleeve gastrectomy (SG) are the three most commonly performed bariatric procedures. Obesity responds well to

bariatric surgery, with major long-lasting weight loss that is most pronounced after RYGB and SG, where the mean

weight loss is about 40 kg or 15 body mass index (BMI) units. Some of the benefits after RYGB and SG are independent

of weight loss, and the remission of type 2 diabetes is observed a few days after the operation; this depends on changes in

insulin sensitivity and gut hormone responses, especially a 10-fold increase in glucagon-like peptide-1 (GLP-1), which

improves insulin secretion. After gastric banding, the remission of diabetes depends more on weight loss. Bariatric sur-

gery reduces cardiovascular risk factors including hypertension, lipid disturbances, non-alcoholic fatty liver, muscu-

loskeletal pain and reduces mortality of diabetes, cardiovascular diseases and cancers. Bariatric surgery also improves

quality of life. The acute complications of surgery are infection, bleeding and anastomotic leak. Long-term complications

are nutritional deficiencies, including vitamins and minerals, and anemia. Some patients have dumping after meals, and a

few patients will develop postprandial hypoglycemia after RYGB. About 25% of patients require plastic surgery to pro-

vide relief from excessive skin tissue.

Keywords: Bariatric surgery, comorbidities, type 2 diabetes, metabolic syndrome, cancer, mortality.

INTRODUCTION

Obesity is a growing worldwide epidemic, which hasgenerated a secondary epidemic of metabolic syndrome,characterized by abdominal obesity, dyslipidemia, hyperten-sion and glucose intolerance associated with increased riskof type 2 diabetes and cardiovascular disease [1,2]. Addi-tional metabolic comorbidities include polycystic ovary syn-drome (PCOS), non-alcoholic fatty liver disease (NAFLD),obstructive sleep apnea (OSA) and several forms of cancers.

Lifestyle changes can lead to a weight reduction of 5-10%, but most individuals start to regain weight after threeto six months, and about 90% return to or even exceed theirinitial weight, indicating that obesity in most cases is refrac-tory to lifestyle therapy [3]. The recent LOOK-ahead trial[4], which randomized 5,145 overweight or obese patientswith type 2 diabetes to either intensive lifestyle interventionor standard care, reported a 6% weight loss after 10 years inthe intervention group vs. 3.5% in the control group. How-ever, the study failed to demonstrate an effect on cardiovas-cular morbidity or mortality [4]. The use of anti-obesityagents may result in a further weight loss of 2-8 kg; thus,with the agents on the market or in development at present,the mean weight loss does not exceed 10 kg in clinical trials

[5].

In contrast, in severely obese individuals, bariatric sur-gery results in major weight loss of 20-30% that is sustainedfor at least 15-20 years [6]. Some bariatric surgery proce-dures are furthermore regarded as metabolic surgery, due

*Address correspondence to this author at the Hvidovre Hospital, Dept. of

Endocrinology, Kettegrd Alle 30, 2650 Hvidovre, Denmark;Tel: +45 38626357/+45 27280918; E-mails: [email protected]

to their beneficial effects beyond weight loss on metabolicsyndrome and type 2 diabetes [7, 8]. The most commonly usedbariatric operation is laparoscopic Roux-en-Y gastric bypas(RYGB), followed by laparoscopic sleeve gastrectomy (SG)and laparoscopic adjustable gastric banding (LABG) [9].

The aim of this review is to provide an update on the ef-fects of RYGB, SG and LAGB on obesity and related comorbidities.

EFFECT OF BARIATRIC SURGERY ON WEIGHTThe Swedish Obese Subjects study (SOS) [6] consisted

of a surgical group (n=2,010) and an obese control group(n=2,037). The groups were matched at 18 clinical variablesPatients in the surgical group underwent adjustable or nonadjustable gastric banding (n=376), vertical-banded gastroplasty (n=1,369) or RYGB (n=265), while those in the control group received customary non-surgical obesity treatmenat their local health centers. In the control group, a maximaweight loss of 1-2% of basal weight was seen, compared to20%, 25% and 32% for adjustable gastric banding, verticalbanded gastroplasty and RYGB, respectively. The maximaweight loss was achieved 1-2 years after surgery. Hereaftersome patients in all surgical subgroups showed a sligh

weight gain, which leveled off after 8-10 years. At the 15year follow-up, the weight loss was 13%, 18% and 27% inthe three surgical groups, respectively [10-12]. Another pro-spective cohort study, LABS-2, reported a mean weight-lossof 41 kg after 3 years in 1738 RYGB operated patients [13]and several studies have shown that weight loss usuallypeaks 1.5 to 2.0 years after surgery [6,14,15].

In a large meta-analysis by Buchwald et al. [8],weighloss, expressed as per cent of excess weight (EBWL), in apopulation of 34,000 patients, was 46% af ter gastric banding

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Bariatric Surgery - Effects on Obesity and Related co-Morbidities Current Diabetes Reviews, 2014, Vol. 10, No. 3 209

and 60% after RYGB; a subgroup analysis (n= 14,000)showed a slightly higher weight loss at 2 years postopera-tively with EBWL of 49% after gastric banding and 63%after RYGB.

In a recent small meta-analysis of randomized controlledstudies, the total weight loss was 26 kg after bariatric sur-gery, but only 381 patients were included; the duration of thefollow-up period varied and the heterogeneity between stud-

ies was very high [16].

SG has been reported to result in similar [17] or slightlylower weight loss than RYGB [18]. In a recent epidemiol-ogical study of 2,949 patients, weight loss (EBWL) afterRYGB, SG and LAGB was 67%, 56% and 44%, respec-tively, 3 years after surgery [18]. Lastly, in a randomizedcontrolled study (RCT) of SG (n=107) vs. RYGB (n=110),an excessive BMI loss (EBMIL) of 72% vs. 77% was re-ported at the 1 year follow-up [17].

The SOS-study, primarily using banding gastroplasty, re-ported that 20-25% of the weight lost after surgery was re-gained by the 10 year follow-up [10-12]. In the Utah-Obesitystudy following 418 patients for 6 years after RYGB, the

weight loss at 2 years was higher than after 6 years, where aregain of 7% of the initial 35% weight-loss was reported[15].

EFFECTS OF BARIATRIC SURGERY ON CO-MORBIDITIES

Effect on Blood Pressure

Bariatric surgery has been reported to ameliorate hyper-tension, with normalization of blood pressure in 30-50% ofpatients 1-2 years after RYGB surgery [13,15,19] and a re-duced need antihypertensive treatment in a further 20-30%of patients [19]. The remission of hypertension seems to beassociated with the degree of weight reduction [19], and pa-tients seem to have a higher remission rate after RYGB thanafter LAGB [13]. Remission of hypertension did not differbetween RYGB and SG in a randomized study [17], but onlya limited numbers of reports have included SG.

Interestingly, in the Utah- and SOS-studies, relapse ofhypertension was seen at the 6 to 10 year follow-up[6,10,15].

The results from the epidemiological retrospective stud-ies discussed here have not been confirmed in randomizedclinical trials including type 2 diabetic patients: Mingrone etal. found no difference in systolic blood pressure betweenpatients undergoing intensive medical treatment and RYGB-

operated patients after 2 years [20], despite the antihyperten-sive treatment being reduced or discontinued in 70% of themedically treated group vs. 80% in the surgery group [20].Ikramuddin et al. only found a modest effect on systolicblood pressure of RYGB after 1 year, but with less medica-tions for comorbidities; however, these were not completelyspecified for hypertension [21].

Effect on Plasma Lipids

Weight loss is associated with an improved lipid profile[22]. In the Utah-Obesity study, dyslipidemia, characterizedby high levels of low-density lipoprotein (LDL) and triglyc-

erides and low levels of high-density lipoprotein (HDL), waresolved 6 years after RYGB in 57-69% of the patients [15]and the remission-rate of dyslipidemia 3 years after RYGBwas 62% in the LABS-2 study [13]. The LABS-2 study alsoreported a remission-rate of 17% after LAGB. Similar resultafter LAGB have been described by Dixon et al.,with favorable changes for fasting triglycerides and HDL-cholestero[22].

In a 24-month follow-up of diabetic patients randomizedto either intensive medical treatment, RYGB or SG, an increase in HDL and decrease in triglyceride were seen [23]and these results were sustained at 3 years [24]. The changewere equal for SG compared to RYGB, while no decreasewas seen for LDL- or total cholesterol [23].

In the SOS-study, the triglycerides did not differ betweenthe surgical and control group at the two and ten year followups, but the reduction in triglycerides was greater in the subgroup treated with RYGB [10]. Buchwald et al. also described an overall improvement in dyslipidemia for all typesof bariatric surgery in approximately 70% of the patients, buthis improvement was not clearly defined [14]. In another

meta-analysis of randomized controlled trials (RCT) [16]only triglyceride- and HDL-concentration changed beneficially after surgery in comparison to controls.

Effect on Type 2 Diabetes

Bariatric surgery has a marked effect on type 2 diabetewith rapidly normalized blood glucose concentrations in themajority of patients. In the meta-analysis by Buchwald et al[8], including 4,973 patients with type 2 diabetes, remissionof diabetes was found to occur in 80% after RYGB and in57% after LAGB. However, subsequent studies have demonstrated that the remission rate of type 2 diabetes depends onthe definition of remission applied. This was exemplified byPournaras et al.in a recent study of 160 patients with type 2diabetes, where diabetes remission was found to occur in41% after RYGB [25] when applying the more strict criteriafor remission from a recent consensus [26]. Preoperativetreatment with insulin was associated with an even lowerremission rate [25]. Nevertheless, overall glycemic controimproved after RYGB, and glycosylated hemoglobin(HbA1c) decreased from 8.0% to 6.2% [25].

Recently, three randomized controlled trials provedRYGB superior to conventional pharmacological treatmenin achieving glycemic control within 1-2 years after surgeryand demonstrated that lower HbA1c levels can be achievedwithout or with less medication after RYGB [20,21,27]. Inone of the studies, a group of SG patients was included, and

the results were comparable to the RYGB operated patientswith respect to improvement in HbA1c and in percentage ofpatients achieving the primary end-point of HbA1c 6.0%42% for RYGB and 37% for SG [24,27]. The same researchers report a slightly smaller remission rate at the 3 year fol-low-up; 38% of patients after RYGB and 24% after SG, buthe glycemic control was still superior to intensive medicatherapy with only 5% of the patients achieving the HbA1ctarget [24]. After 3 years HbA1c declined from 9.3%, 9.5%and 9.0% at baseline to 6.7%, 7.0% and 8.4%; and the bodyweight change from baseline was -26.2 kg, -21.3 kg and -4.3kg for RYGB, SG and the medically treated group, respec-

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210 Current Diabetes Reviews, 2014, Vol. 10, No. 3 Svane and Madsbad

tively. Furthermore the use of glucose-lowering medicationswas lower in both surgical groups [24].

Also, LAGB has shown superiority in the treatment of

type 2 diabetes when compared to intensive pharmacological

and lifestyle intervention. In a randomized controlled study

with a 2 year follow-up period, the remission rates were 73%

for LAGB and 13% for the control group [28]. Diabetes re-

mission was related to weight loss and lower baseline

HbA1c levels [28]. Compared to RYGB, patients treated

with LAGB appeared to experience a lower rate of diabetes

remission.

The SOS-trial reported a higher remission rate of diabe-

tes after 2 (OR 8.4, CI 5.7-12.5) and 10 years (OR 3.5, CI

1.6-7.3) compared with the control group, but a 50% relapse

was observed at 10 years (remission rate 72% at 2 years and

36% at 10 years) [6]. In addition, bariatric surgery reduced

the incidence of type 2 diabetes (hazard ratio (HR) 0.22, CI

0.18-0.27) in the follow-up period of up to 15 years (mean

10 years) compared with the control group; this was most

efficient in patients at high risk due to impaired fasting glu-

cose (IFG) at baseline (number needed to treat (NNT) in

order to prevent one case of type 2 diabetes was 1.3 in pa-

tients with IFG and 7.0 in patients with normal fasting glu-cose) [6,29].

The remission rates seem to be associated with the dura-tion [24] and degree of glycemic control before the operation

[30]. Other predictors are C-peptide (beta-cell function),

preoperative glucose-lowering treatment (insulin vs. oral),preoperative body mass index (BMI) and weight loss [31].

Relapse of diabetes is associated with failing beta-cell func-

tion. Recurrence rates of diabetes in recent epidemiologicalstudies with long-term follow-up (> 5 years) were 13-35%

after RYGB [15,30,32], and were associated with weight

regain, longer duration of diabetes, poor preoperative glyce-

mic control and insulin treatment before surgery [30].

The effect on diabetes seems to include the improvement

or delayed progress of end-organ complications such as reti-nopathy and nephropathy in addition to improved glycemic

control [33].

Effects on Metabolic Syndrome

Before surgery, most obese patients will display symp-

toms of metabolic syndrome, with components of high

triglycerides, low HDL, hypertension, high plasma glucose

and waist circumference. Batsis et al. found the prevalence

of metabolic syndrome to be decreased after 3.4 years of

follow-up from 87% to 29% in response to RYGB comparedto a decrease from 85% to 75% in the conventional lifestyle-

intervention control group [7]. The strongest predictor for

resolution was loss of body weight [7]. Furthermore, the

authors estimated that four deaths and 16 cardiovascular

events per 100 patients would be prevented by bariatric sur-

gery during a 10-year period.

Vidal et al.retrospectively compared diabetic patients af-

ter RYGB and SG and found comparable resolution rates of

both diabetes (85% in each group) and metabolic syndrome

(67% vs. 62%) [34].

In a recent study using the Bariatric Outcome Longitudi-nal Database, 23,106 patients were identified to have metabolic syndrome before surgery [35]. The 1 year resolution ofhypertension, diabetes and dyslipidemia after LAGB was19%, 28% and 17%, respectively, compared to 45%, 62%and 45%, respectively, after RYGB, and 35%, 52% and34%, respectively, after SG [35].

Effect on Non-alcoholic Fatty Liver DiseaseAfter bariatric surgery, a reduction in liver steatosis, in

flammation and fibrosis was observed 15 months afterRYGB, SG or LAGB [36]. Thus, inflammation and fibrosiwere completely resolved in 37% and 20% of the patientsrespectively. In another study, NAFLD resolved in 89% ofRYGB-operated patients [37].

Effects on Cardiovascular Disease and CardiovascularMortality

Bariatric surgery has beneficial effects on cardiovascularrisk factors such as left ventricular hypertrophy [38], carotisintima thickness, and flow-mediated vessel dilatation [39].

Moreover, the resolution of diabetes, hypertension andhyperlipidemia postoperatively results in an overall 10 yeareduction in the coronary heart disease Framingham riskscore from 6% to 3% [38], and other researchers have foundan even better improvement in the risk score [40], which wamost pronounced in men.

In the SOS-study, the number of cardiovascular eventwas 234 in the control group vs. 199 in the surgery group(HR 0.83, CI 0.69-1.00), and the number of cardiovasculardeaths was 49 vs. 28 (HR 0.56, CI 0.35-0.88), respectively[12]. Surgery was also associated with a reduced number offatal myocardial infarctions [12]. Insulin resistance at baseline rather than BMI predicted the beneficial effects of sur

gery [12]. In type 2 diabetes patients, bariatric surgery alsoreduced the incidence of cardiovascular events after a follow-up period of 13 years (adjusted HR 0.56, CI 0.34-0.93[41] compared with the control group. NNT to prevent onemyocardial infarction in a 15 year period among the obesediabetic population was 16 [41].

In the retrospective study by Christou and co-workerswhich compared 1035 patients after bariatric surgery (81%RYGB, 19% vertical banded gastroplasty) with 5,746matched control subjects during a five year follow-up, therisk reduction in cardiovascular disorders was 82% in favorof surgery [42]. Likewise, in the study by Adams et al.which compared 7,925 patients after RYGB with the samenumber of matched controls, the reduction in mortality ocoronary artery disease was 56% [43].

Effect on Obstructive Sleep Apnea

A meta-analysis of 69 studies including 13,900 patientsindicated that bariatric surgery resolves or improves OSA inmore than 75% of patients with this condition, with the mospronounced effect being reported after RYGB, followed bySG and LAGB, probably reflecting the degree of weight losachieved by patients following these procedures [44]. Otheinvestigators have presented similar results [14,45,46]. Interestingly, a randomized study of conventional weight loss

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therapy vs. LAGB found no difference in OSA resolutiondespite major differences in weight loss [47].

Effect on Musculoskeletal Pain

Obesity is associated with musculoskeletal pain [48]. Re-sults from the SOS-study report an increased recovery aswell as a reduced incidence of work-restricting muscu-loskeletal pain after bariatric surgery; furthermore, the re-

covery-rate was related to the degree of weight loss follow-ing surgery [48].

Effects on Cancers

After a 10.9 year follow-up period in the SOS-study, thenumber of first time cancers in the surgery group was re-duced compared with the control group (HR 0.67, CI 0.53-0.85; p= 0.0009) [6]. In women, the number was 79 vs. 130patients, respectively (HR 0.58, CI 0.44-0.77; p= 0.0001),whereas there was no effect of surgery reported in men.

Christou et al. reported 21 cancers in the surgery group(n=1,035, 82% RYGB) compared with 487 cancers in thecontrol group (n= 5,746), with a Relative Risk (RR) of 0.22

(CI 0.14-0.35 p=0.001) after a maximum follow-up of fiveyears [49]. Adams et al.found that the reduction in cancer-caused mortality was 61% after a mean follow-up of 7.1years [43]. In a later follow-up, after a mean of 12.5 years, a24% reduction in cancers was found in the surgical groupcompared with the control group, whereas the overall cancermortality was reduced by 46% [50]. In particular, the inci-dence of uterine cancer was significantly lower among surgi-cal patients.

The quality of the studies, except for the SOS-studies, ispoor and randomized controlled studies with long-term fol-low-up are needed to obtain robust data on the effects of

bariatric surgery on the risk of developing cancer.

Effects on Mortality

In the SOS-study, after an average of 11 years follow-up,the cumulative overall mortality was 129 subjects (6.3%) in

the control group compared with 101 (5.0%) in the surgerygroup, indicating a relative risk reduction of 24% (HR 0.76,

p= 0.04) [11]. The reduction in mortality was more pro-nounced in subjects with a higher BMI, with a reduction in

the risk of death of about 30% in subjects with a BMI abovethe median of 40.8 kg/m2 and 20% in subjects below the

median [11].

Adams et al. retrospectively followed 7,925 people forseven years and found a 40% reduction of total mortality in

the surgical group compared with a control group of subjectsmatched for age, sex and BMI [43]. In a third study, the re-

duction in all-cause mortality was 89% in the surgical groupcompared with a control group after at least five years of

follow-up [42]. A limitation of all three studies is that thedesigns were not randomized and controlled and no informa-

tion on baseline morbidity was presented.

A meta-analysis from 2011 reported an overall reductionin all-cause mortality of 45% (OR 0.55, CI 0.49-0.63), but

the included studies were not randomized and the heteroge-neity of the studies was very high [51].

Effects on Quality-of-Life

The substantial and long-term weight loss following bariatric surgery has a beneficial effect on the quality-of-life inmost patients [52-54]. Furthermore, the degree of weightloss appears to affect the quality-of-life improvements [5254], and health-related quality-of-life over a 10 year periodfollowed phases of weight loss, weight gain and weight sta-bility, and was related to the magnitude of weight loss and

weight regain in the SOS-study [53]. In contrast, Adams eal.found no improvement in a mental component score afterbariatric surgery compared with two obese control group[15], and other authors have suggested an increased risk ofsuicide after RYGB [43].

RISKS OF BARIATRIC SURGERY

In the best centers, the 30 day mortality is about 0.2-0.4%after laparoscopic RYGB [55,56] and below 0.1% after gas-tric banding [14,56]. The acute complications are bleedinginfections, anastomotic leak, arrhythmias and venous embolism. The risk of serious complications is reported to be4.8% for laparoscopic RYGB and 1.0% for LAGB [55], and

the total complication rate is about 17% [56]. Long-termcomplications after RYGB include internal hernias and anastomotic stenosis with vomiting, stoma ulceration erosionsand nutritional deficiencies [57] and the patients need to besupplementedwith vitamins and minerals. Some of the longterm risks are not seen after SG; instead, there is a longerstable-line of the stomach with associated risk of leakageSG in general seems to cause fewer minor complicationthan RYGB [58] but the published data include only a smalnumber of patients and further studies are needed.

Some patients will develop dumping, with symptoms

such as abdominal pain and cramping, sweating, dizzinessnausea, tachycardia and diarrhea. Dumping symptoms be

come less prominent over time [57]. Few patients will de-velop postprandial symptomatic hypoglycemia, presumablybecause of an imbalance of excessive insulin secretion due to

an exaggerated GLP-1 response and improved insulin sensi-tivity [59].

In summary, RYGB seem to have the highest rates ocomplication, followed by SG and LAGB, but the overalmortality is low.

DISCUSSION

Obesity is accompanied by comorbidities, making obe-sity a major threat to health. Treating obesity has been

proven to be difficult and ineffective, and it is often consid

ered to be a self-induced behavioral problem of the patientthemselves instead of a physiological dysregulation. Manypeople often overestimate the benefits of lifestyle and phar

macological interventions, but unfortunately, lifestyle andpharmacological treatments rarely result in sustained weighloss, and many physicians consider obesity an intractable

disease.

The only effective treatment for obesity is bariatric sur-

gery, providing substantial long-term weight loss, which ismost pronounced following RYGB and SG. The weight loss

after LAGB is slower and less pronounced.

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Obesity is associated with accelerated atherosclerosis andimprovements in the CVD risk factor profile, includingmetabolic syndrome; a lower risk of ischemic heart diseaseand mortality has been demonstrated after bariatric surgery.Thus, improvements in hypertension and especially the lipidprofile associated with metabolic syndrome, which is charac-terized by high triglycerides and low HDL cholesterol, havebeen reported. The effect on LDL cholesterol seems to be

minimal. The weight loss after bariatric surgery also improvesNAFLD, OSA, musculoskeletal pains and quality-of-life.

Increased body adiposity is an established risk factor forthe development of cancer. Although the studies may becriticized, several have provided evidence that weight reduc-tion in obese individuals is associated with a subsequent re-duction in cancer incidence. The effect seems limited towomen, and the reductions are most robust for breast cancerand endometrial cancers, which are both hormone-sensitive.It is unknown whether different bariatric procedures mayhave different effects on the incidence of cancer.

Bariatric surgery also prevents new cases of diabetescompared with lifestyle treatment. A robust finding in many

studies, independent of bariatric procedure, has been im-provements or remission of type 2 diabetes already a fewdays after surgery, before any significant weight loss. Thisobservation has introduced the term metabolic surgery,because of the marked modification of type 2 diabetespathophysiology for the better without any weight loss. Ran-domized studies have shown the superiority of bariatric sur-gery compared to an intensive lifestyle and medical man-agement in relation to both weight loss and remission of dia-betes, but all of the studies have been of short duration andhave included only few patients. Larger and longer trials areneeded to estimate the benefit of bariatric surgery comparedwith the conventional treatment of type 2 diabetes. The re-mission rate of diabetes is higher and faster after RYGB and

SG than after LAGB, but for all procedures, diabetes remis-sion trended downwards over time.

The effects of all three procedures on glucose metabo-lism are explained by anincrease in hepatic insulin sensitiv-ity, which is induced at least in part by calorie restriction,and can be observed only a few days after surgery [60,61].No hormonal changes explain the weight loss and remissionof type 2 diabetes after LAGB. After RYGB and SG, an im-proved postprandial insulin secretion, associated with anexaggerated postprandial glucagon-like peptide-1 (GLP-1)secretion due to altered transit time of nutrients to the termi-nal ilium, is seen [60]. Thus, the physiological explanation ofthe remission of type 2 diabetes relies on GLP-1 and im-proved beta-cell function after RYGB and SG, which canalso explain the lower diabetes remission rate in patientswith advanced disease and longer duration and thus failingbeta-cell function. Later, a weight loss-induced improvementin peripheral skeletal muscle insulin sensitivity is the finaldeterminator of glucose tolerance after all three procedures[61].

The explanation of weight loss also differs between thethree procedures. After LAGB distension, stimuli from thesmall pouch above the band may be transmitted viaafferentvagal nerves to areas of the central nervous system that areimplicated in satiety and reducing food intake [62]. The

changes in food texture and eating small volumes to preservedigestive comfort may also explain modified eating behaviors and thereby part of the weight loss. Following RYGBand SG, increased postprandial responses of GLP-1, peptideYY (PYY) and oxyntomodulin seem to stimulate anorecticpathways in the hypothalamus and brain stem, leading toreduced appetite and food intake.

In a position statement from 2011, the International Dia

betes Federation (IDF) recognized bariatric surgery as an appropriate treatment for type 2 diabetes if recommended glycemic targets are not reached with the available medical therapies, especially if hypertension and dyslipidemia also exist.

CONCLUSION

Thus, bariatric surgery results in substantial weight losswith excellent beneficial effects on comorbidities to obesitybut with the cost of surgical and medical complications, i.efrom micronutrient deficiencies, which require life-longmonitoring. Many patients will also need to undergo plasticsurgery to provide relief from excessive skin tissue, and thiis expensive and may induce new complications.

This review has also revealed the shortcomings of manystudies. Studies with long-term follow-up periods are limited

and often report poor retention of participants. Another mainlimitation in many studies is their lack of randomization; thequality of studies varied from very few randomized studiesto retrospective cohort studies without a control group. Stan

dardized definitions for the resolution of co-morbidities arealso needed for comparisons of the results of future studiesLonger and larger clinical trials comparing lifestyle andpharmacological treatments with bariatric surgery are an

unmet need. Although RYGB and SG are more effectivethan LAGB for the reversal of obesity and diabetes, they alsoconfer greater surgical risks; therefore, long-term studiecomparing the different procedures are warranted.

The effects of bariatric surgery are intriguing and have

created a new understanding of the pathogenesis of obesityand type 2 diabetes; however, it is impractical to performsurgery in all obese people. A goal must be to develop lessinvasive methods, and ultimately, understand the effects of

bariatric surgery on metabolism beyond that expected oweight loss, which may enable the development of new ef-fective therapeutic strategies for weight loss and the treatment of diabetes.

CONFLICT OF INTEREST

The authors confirm that this article content has no

conflict of interest.

ACKNOWLEDGEMENTS

Declared none.

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Received: March 25, 2014 Revised: May 17, 2014 Accepted: June 13, 2014

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