Introduction

The obesity epidemic is accelerating globally1 with prevalence in the UAE among adults expected to reach 40.6% by 2030.2 The benefit of MBS in the treatment of obesity and its associated comorbidities is well-established,3–5 with increased longevity demonstrated in surgically treated patients compared to controls.6 Studies contributing to these pooled data, however, come mostly from Europe, North America, and Asia, but none originate from the Middle East. This contrasts with the relatively large number of MBS operations performed in the region. In a survey of 50 countries worldwide, the contributing Gulf nations, Kuwait, Saudi Arabia and UAE, each ranked in the top third (2nd, 14th and 15th respectively) by number of procedures done as a proportion of national population.7 Despite the proliferation of MBS services, only a few small retrospective studies have been published on outcomes from the Gulf region.8

While many factors affect response to MBS, some variables most associated with change in weight have been reported as type of procedure, followed by demographic characteristics, such as age, baseline weight and ethnicity.9,10 There have been no studies to date investigating comparative outcomes for Arab ethnicity. However, regional variations in choice of procedure and demographics have been published. In the 8th International Federation for the Surgery of Obesity Global Registry Report, baseline characteristics are described for patients from 21 countries who underwent MBS in 2022. The Gulf states are represented by Kuwait, which had the highest proportion of patients who had primary SG at 90% (836/934) and compares to 67% for USA and a global average of 62.5%. Kuwait had the second youngest group, with median age of 34 years at the time of surgery, and the highest proportion of male patients (33%).11 Demographics are similar in the UAE where the national population is young, with median age 33 years, compared to USA with median age 38 years and the European Union at 44 years.12,13 In this study, metabolic outcomes are reported from our center in the UAE, where SG is also the preferred primary procedure, and patients are predominantly Emirati. Changes in weight and remission rates of T2D, hypertension, and hyperlipidemia were assessed, and then compared to internationally reported outcomes.

Methods

This single-center retrospective study was approved by the Imperial College London Diabetes Centre Research Ethics Committee in January 2024 (approval reference number: IREC090) and registered with the Department of Health in Abu Dhabi. All patients signed consent forms allowing the use of anonymized data for research purposes. The study was conducted in accordance with the Declaration of Helsinki.

Our center is a collaboration between a specialist surgical hospital and a metabolic outpatient clinic with branches on three sites situated within the Emirate of Abu Dhabi in the United Arab Emirates. The metabolic clinic provides follow-up in a medical service and is staffed by bariatric physicians who form part of the multidisciplinary team at the Bariatric and Metabolic Surgery Center. All patients are advised to attend long-term follow-up in the metabolic clinic. While many come from distant Emirates, the majority re-attend regularly after completing the 30-day surgical follow-up. Prior to surgery, patients have a minimum of two dietician visits and are assessed by a psychologist. Patients are counselled on the importance of long-term follow-up, adherence to dietary recommendations, exercise, and nutrient supplementation. Following surgery, patients visit a dietician at 1-week and 1-month, then at 3-month intervals for two years. Thereafter, a 6-monthly follow-up interval is encouraged. The recommended daily protein intake is 60 g or more, depending on weight.

Patients were included who had primary MBS at the center’s specialty hospital and who then attended follow-up in the metabolic clinic between May 2016 and 31 December 2022. Patients who had undergone revision surgery were excluded from the study. Baseline data were sourced from the hospital database, and outcomes from the electronic records of the metabolic clinic. Age at the time of surgery, sex, ethnicity, height, weight, BMI, HbA1c, number of diabetes medications, low-density lipoprotein (LDL), high-density lipoprotein (HDL), total cholesterol (TC), triglyceride (TG) levels, number of lipid-lowering medications, systolic blood pressure, diastolic blood pressure, and number of antihypertensive agents were recorded. Patients with a pre-existing diagnosis of T2D, hyperlipidemia, or hypertension before surgery were included in the analysis of the status of each metabolic disease as per the ICD10 classification codes E11, I10, and E78, respectively. Data were gathered at 3-, 6-, 12-, 18-, 24-, 36-, 48-, and 60-month follow-up visits.

T2D total remission was defined as HbA1c <6.5%, off all diabetes medications, consistent with the American Diabetes Association (ADA) consensus statement from 2021.14 Complete remission was defined as HbA1c <6.0% without medication. More stringent criteria were favored previously by the ADA, and many studies have reported using both. T2D improvement is HbA1c reduction and/or a reduction in the number of diabetes medications. Complete remission of hypertension was defined as blood pressure (BP) <120/80 mmHg without any antihypertensive medication, consistent with the standard definition of normal BP as per ACC/AHA guidelines.15 Total remission (complete + partial) is BP <140/90 mmHg without medication. Hypertension improvement is lower BP and/or fewer antihypertensive agents. Hyperlipidemia remission was defined as normal lipid profile without lipid lowering medication, where normal is LDL <2.6 mmol/L and TG <1.7 mmol/L. Improvement was defined as a reduction in LDL levels or fewer lipid-lowering medications. The proportion of patients achieving a TC:HDL ratio <3.27 without lipid lowering medication as an additional measure of reduced cardiovascular risk was also assessed. The above definitions and cut-offs are consistent with the American Society for Metabolic and Bariatric Surgery guidelines on metabolic outcomes reporting published in 2015.16

The two procedures conducted at our center were SG and RYGB. Procedure selection was based on patient choice and absence of contraindications. Patients with proven gastro-esophageal reflux disease were offered RYGB. Contraindications for SG include Grade B esophagitis and Barrett’s esophagus. Esophagogastroduodenoscopy was performed selectively in patients with clear reflux symptoms and a GERD-Q score ≥8. In our center, smokers, patients with inflammatory bowel disease or a hostile abdomen are excluded from having RYGB, whereas patients with T2D may be encouraged to have RYGB. Procedures were performed by two consultant bariatric surgeons at the center. SG was performed by the same technique for each surgeon. For RYGB, an alimentary limb of 100 cm was formed, with a biliary limb of 100 cm by one surgeon and 80–100 cm by the other.

Statistical Analysis

Statistical analysis was performed using R version 4.3.1 (R Foundation for Statistical Computing, Austria). Baseline characteristics were presented as mean (standard deviation), normally distributed, or median (interquartile range). Outcome estimates are presented as mean (95% confidence interval of the population mean). Comparisons between groups were evaluated using the chi-square test. Exploratory analyses of the influence of pre-operative factors on 12-month weight loss and diabetes remission were performed using linear and logistic regressions, respectively. Differential effects of the procedure on weight loss at each time point were explored using two-way analysis of variance (ANOVA) with post-hoc comparison performed using 2-tail Student’s t-test. Statistical significance was determined at p<0.05.

Results

A total of 3763 patients underwent primary surgery at the center’s hospital during the study period, of whom 2851 attended follow-up appointments in the bariatric clinic and could be included in the study. Of the included patients, 2637 underwent SG and 214 underwent RYGB procedures. Baseline characteristics of included patients were as follows: 1786 patients were female (62.6%); mean age at operation was 34.2 ±10.2 years and median BMI 41.0 (37.8–45.2) kg/m2. Emirati patients numbered 2681 (94.0%), 143 (5.0%) were of other Arab nationality, and 27 (1.0%) were non-Arab. A total of 541 individuals (20.2%) had a preceding diagnosis of T2D, 1297 (48.4%) had hyperlipidemia, and 434 (16.2%) had hypertension. In the T2D subgroup, the median HbA1c level before surgery was 7.1% (6.3–8.2). The baseline characteristics stratified by surgery type and sex are shown in Table 1.

Table 1 Baseline Characteristics Stratified by Surgery Type and Gender

Follow-up Rates

The proportion of all operated patients who attended metabolic clinics 1, 3, and 5 years after surgery was 60.2% (1730/2873), 43.7% (631/1445) and 33.8% (156/412), respectively. Calculation of the follow-up rate only included patients who could have feasibly attended, given the timing of their surgery. For example, only patients who underwent surgery before the end of 2017 may have contributed to the 5-year outcome data. Of the 912 operated patients who did not attend the metabolic clinic, 228 continued to attend the surgical clinic with access to other bariatric MDT support. Thus, the proportion of patients who did not attend any specialist follow-up after 3 or more months was 18.2% (684/3763). The selection of patients included in the study population is represented in Figure 1. The number of operations by date performed for the study population is shown in Supplementary Figure 1.

Figure 1 Patient disposition.

Abbreviations: SG, sleeve gastrectomy, RYGB, Roux-en-Y gastric bypass.

Weight Change

Weight loss expressed as mean %TWL (95% CI) for SG patients was 29.9% (29.5–30.3, n=1587) and 23.4% (21.6–25.2, n=143) at 12 and 60 months respectively. For RYGB the %TWL was 31.2% (30.0–32.5, n=143) and 28.4% (23.0–33.8, n=13) at the same time intervals (see Figure 2a and values for each timepoint in Table 2). The highest degree of %TWL following SG was reached at 18 months in both women and men. For women who underwent SG, this was 29.0% (28.3–29.6, n=720) and 32.8% (31.8–33.8, n=395). At 5 years mean %TWL for women was 22.1% (19.9–24.2, n=83) and 25.2% (22.1–28.3, n=60) for men (see Figure 2b). Weight recurrence after 5 years as proportion of the maximum recorded %TWL for patients with paired data at 18 and 60 months was 12.6% (3.6–21.6, n=63) for women vs 19.0% (10.2–27.8, n=43) for men.

Table 2 Percentage Total Weight Loss by Type of Surgery With 95% Confidence Intervals

Figure 2 Percentage total weight loss post-surgery for (a) Roux-en-Y gastric bypass and sleeve gastrectomy and (b) Sleeve gastrectomy split by male and female. Population mean with 95% confidence interval; * = p<0.05; ** = p<0.01; *** = p<0.001.

Abbreviations: LRYGB, laparoscopic Roux-en-Y gastric bypass; LSG, laparoscopic sleeve gastrectomy.

Combining both sexes for the SG group, the maximum mean %TWL at 18 months was 30.3% (29.8%-30.9%, n=1115), falling at 5 years to 23.4% (21.6%-25.2%, n=143). Weight recurrence in this group as a proportion of the peak %TWL for patients with paired data at 18 and 60 months was 14.9% (8.5–21.2, n=108). The complete values for weight change by surgery type, split by male and female, are listed in Supplementary Table 1.

With respect to factors associated with %TWL, both timepoint and procedure type were found to be significant in the two-way ANOVA. In post-hoc testing, %TWL differed significantly between the RYGB and SG groups at 12 and 36 months, but not at 5 years (p=0.103). The significance tests for each timepoint are shown as p-values in Table 2. Regression analysis was performed to identify the predictors of weight loss at 12 months (see Figure 3a). Male sex and RYGB showed strong associations with increased %TWL, as did taking oral hypoglycemic agents. A higher BMI and younger age were also associated with greater weight loss. Regarding the use of pharmacotherapy, 6.1% of the patients were taking GLP1 receptor agonists (GLP1RAs) during the postoperative follow-up period (25.2% of those with T2D vs 2.1% without T2D).

Figure 3 Forest plot of variables of interest for (a) Percentage total weight loss at 12 months, (b) Type 2 diabetes complete remission at 12 months.

Abbreviations: %TWL, percentage total weight loss; BMI, body mass index; OHA, oral hypoglycemic agent; LSG, laparoscopic sleeve gastrectomy; LRYGB, laparoscopic Roux-en-Y gastric bypass; CI, confidence interval; OR, odds ratio.

Type 2 Diabetes

For patients who underwent SG, the total T2D remission rates (HbA1c <6.5% without medications) were 61.9% (n=179/289), 37.8% (62/164), and 40.9% (18/44) at 1, 3, and 5 years, respectively. The complete remission rates (HbA1c <6.0% without medications) following SG were 53.6% (155/289), 34.1% (56/164), and 34.1% (15/44), respectively. For those who underwent RYGB at 12 months, total remission was achieved in 61.4% (n=35/57) and complete remission in 56.1% (n=32/57). The total and complete remission rates for T2D by type of surgery are listed in Supplementary Tables 2a and 2b, while the improvement and remission rates are illustrated in Figure 4. Differences in baseline characteristics between the surgical groups should be considered as they affect the likelihood of remission. RYGB patients with T2D had a higher starting median HbA1c level of 7.6% vs 7.1% for SG. Also, more RYGB patients were taking insulin prior to surgery, 23.8% vs 16.0%, although SG patients took more oral hypoglycemics pre-operatively (see baseline characteristics of T2D subgroup in Table 3). However, these variables were controlled for in the regression analysis, which suggested that patients who underwent RYGB were more than twice as likely to achieve complete T2D remission at 12 months OR=2.272 (1.152–4.65). As expected, there was a reduced likelihood of remission associated with older age, higher HbA1c, pre-operative insulin use, and use of oral hypoglycemic agents (see Figure 3b).

Table 3 Baseline Characteristics of Type 2 Diabetes Subgroup

Figure 4 Type 2 diabetes improvement and remission over time for (a) Roux-en-Y gastric bypass and (b) Sleeve gastrectomy. Proportion of population with 95% confidence intervals.

Hyperlipidemia

Overall, hyperlipidemia improvement and remission are illustrated in Figure 5a. Hyperlipidemia remission following SG was observed in 16.4% (78/475), 14.3% (11/217), and 10% (10/64) of patients at 1, 3, and 5 years, respectively, while in patients who had RYGB the remission rate was higher at 41.8% (23/55) at 1 year. The complete values for changes in the status of hyperlipidemia are listed in Supplementary Table 3. Looking at both surgical groups overall, the number of patients achieving TC:HDL ratio <3.27 without medication was 50.2% (283/564), 54.5% (132/242) and 47.8% (33/69) after 1, 3 and 5 years respectively.

Figure 5 Change in status over time after any surgery for (a) hyperlipidemia and (b) hypertension. Proportion of population with 95% confidence intervals.

Hypertension

The improvement and remission of hypertension in the hypertension subgroup are illustrated in Figure 5b. In patients who underwent SG, total remission (BP <140/90 mmHg without medication) was achieved in 68.1% (179/263), 55.8% (92/165), and 44.4% (20/45) of patients at 1, 3, and 5 years, respectively. Complete remission of hypertension following SG (BP <120/80 mmHg without medication) was observed in 32.7% (86/263), 20.0% (33/165), and 8.9% (4/45) of patients, respectively. Following RYGB, total remission of hypertension was observed in 58.6% (17/29) of patients and complete remission in 24.1% (7/29). All values for complete and total remission according to the surgical type are listed in Supplementary Tables 4a and 4b. The difference in hypertension remission rate between the SG and RYGB groups was not significant at 12 months.

Discussion

Weight loss was satisfactory for the majority of patients in our cohort, with a similar %TWL observed for RYGB and SG at one year. However, beyond 18 months, the gap in the mean %TWL between the procedures appears to widen. Weight loss in the RYGB group decreased from 31.2% (30.0–32.5) at 1 year to 28.4% (23.0–33.9) after 5 years, while for patients who had SG, the mean %TWL fell by a greater margin, from 29.9% (29.5–30.3) to 24.4% (21.6–25.2) over the same period. A systematic review reporting %TWL found a pooled mean weight loss of 29.5% in 3542 patients across 13 studies at 1 year post-SG and a pooled mean %TWL at 5 years of 27.0% in 787 subjects from five studies,17 suggesting a less favorable outcome for our SG cohort at 5 years. If weight recurrence is expressed as a proportion of %TWL at 1 year, then this is an increase of 18.4% from years 1 to 5 in our cohort compared to a smaller gain of 8.5% in the systematic review. So, weight recurrence following SG in our cohort was higher than the international average. Another way to illustrate the change in outcome is to consider the proportion of patients achieving suboptimal response with %TWL <20%, which for SG at 1 year in our cohort was 10.8% (171/1857) and then markedly higher after 5 years at 44.1% (63/143).

While the reduced weight loss in our population is not yet fully explained, reasons are likely to be multifactorial and include genetic and epigenetic factors. Consanguinity is relatively high in the Arabian Gulf and might contribute to an increased prevalence of monogenic obesity (MO), which may, in turn, affect the outcome of MBS. One study from Qatar identified genetic variants associated with MO in more than 5% of 250 individuals with BMI >35.18 A recent study of an Emirati cohort reported genetic mutations associated with MO in 15.6% of patients with BMI >50 (n=190) and found that they responded less well to MBS than controls.19 Evidence for polygenetic effects on treatment outcome has been presented in several studies. A systematic review reported associations with weight loss in 6 out of 7 studies assessing genetic risk scores using between 7 and 186 single nucleotide polymorphisms ranging from 12 to 96 months post-surgery.20 Another study demonstrated similar response to RYGB in first degree relative pairs.21 Other cultural, behavioral, social and psychological factors may be at play. Familial influence on eating habits, dietary compliance, adherence to follow-up plans, quality of nutrition and attitudes to exercise have all been implicated in studies on Arab populations.22 While population specific or regional impacts on outcomes may exist, the extent to which they apply to our cohort is unclear. For example, poor communication of dieticians’ instructions and low levels of dietary adherence have been reported in one study from the UAE.23 On the other hand a Jordanian study found nutritional counselling improved quality of food intake after SG,24 and another study from UAE reported an association between number of dietician visits and weight loss 12 months after SG.25 While patients from our center are expected to have demonstrated the ability to follow dietary instructions as a pre-condition for surgery and seen Arabic-speaking dieticians multiple times as part of routine medical follow-up, the extent to which they actually did so cannot, unfortunately, be measured from the available dataset. Prospective studies assessing patient adherence to lifestyle recommendations are needed to assess the behavioral determinants of these outcomes.

While GLP1RAs are an increasingly potent treatment for obesity26 and have been shown to be well-tolerated and equally effective when combined with MBS,27 the proportion of patients taking GLP1RAs in our cohort was small, only 2.1% of those without T2D. This was most likely due to limited access to pharmacotherapy, as obesity management medications were not funded by local insurers.

A large majority of patients in the study chose SG above RYGB (92.5%), a proportion similar to that seen in Kuwait. Our cohort was relatively young (mean age 34 years), and a relatively high proportion of patients were male (37.4%). Reasons for the regional preference for SG likely include patients not wanting to commit to as much long-term micronutrient supplementation, perceptions about not wanting to alter the route of food ingestion, the relatively unfavorable reputation and misconception of side effects of RYGB, surgeons preferring SG and being less well trained in RYGB, and the high prevalence of smoking.

Male sex was strongly associated with increased weight loss at 12 months after SG. While men were younger than women (32.4 years vs 34.8 years, respectively) and fewer had T2D (16.1% vs 18.1% respectively), these variables were also controlled for in the regression analysis. To the best of our knowledge, this is a novel finding and the cause remains unclear. One may surmise that biological factors such as pregnancy, use of hormonal contraceptives, and fertility treatment have affected outcomes. Other cultural influences, such as prohibitive family influences on outdoor exercise or access to gym facilities, may have played a part. Additionally, differing occupational motivations can affect adherence to lifestyle interventions. Promotions at work can be made conditional on meeting certain weight thresholds, a common practice in the military and police force that tend to involve men more than women.

T2D remission at 12 months was more likely following RYGB than SG, which mirrors a meta-analysis published in 2021.28 In this review, RYGB was associated with a greater likelihood of complete remission (HbA1c <6.0%) at 1-year post-surgery (OR = 1.22; 95% CI 1.06–1.40), but with no difference by surgery type after 3 and 5 years. Remission rates in the contributing RCTs were of the same order as those in this study, albeit with noted heterogeneity between studies. The total remission rate in our cohort (HbA1c <6.5%) 1 year after SG was 61.9% (179/289) compared to a mean of 55.0% across five studies (range 40.0–71.7%, 112/203) included in the meta-analysis,29–33 while this reduced to 40.9% (18/44) in our population compared to 23.4% (11/47) and 36.6% (15/41) in two studies at 5 years.30,34 Thus, while RYGB may be preferred for our patients with T2D, SG can be considered an effective and relatively durable alternative.

The rate of hyperlipidemia remission in our cohort was significantly greater for patients who underwent RYGB than for those who underwent SG 12 months after surgery. A meta-analysis of seven RCTs found an increased likelihood of remission following RYGB compared to SG (OR 2.28, 95% CI 1.21–4.29), albeit over different observation periods of 36 to 60 months.35 However, hypertension outcomes in our cohort did not show any significant difference in remission rate between RYGB and SG after 1 year, in contrast to a meta-analysis of 8 RCTs, where an increased likelihood of hypertension remission was reported following RYGB compared to SG (OR 1.55, CI 1.20–2.00) for follow-up periods ranging from 1 to 5 years.36 Comparing remission rates for both hyperlipidemia and hypertension is more challenging, as the majority of contributing RCTs define remission as cessation of relevant medications only, without specifying a normal threshold for BP or lipid profile.

Data published from the Middle East are limited. Few retrospective studies have reported outcomes using percentage excess weight loss (EWL), making comparative analysis difficult. Some moderately sized studies of several hundred patients each reported favorable EWL for periods ranging from 3 to 8 years,37–40 while two small studies from the Gulf region reported T2D improvement by change in HbA1c in 20 to 70 patients with up to 2 years of follow-up.41,42

The main strengths of this study were the size and duration of follow-up. It is thus far the largest outcome study to come from the UAE and has been able to show the important difference in outcomes between women and men, as well as reveal the trend of weight recurrence up to 5 years following SG. The subgroups were also large enough to demonstrate the superiority of RYGB over SG for T2D remission at one year, which is important evidence to help guide local practice. Limitations to this single-center retrospective study should be highlighted. Missing data and the variable quality of manually written notes prevented the inclusion of certain parameters, such as duration of diabetes and individual nadir weight. Re-operation rate could not be assessed. Furthermore, our patients came from all over the UAE, and a significant proportion of operated patients did not attend metabolic follow-up at 3 or more months and thus were not included. Attendance was also compromised by the Covid19 pandemic. Another drawback was the small number of patients who had RYGB compared to SG, which limited the utility of comparisons at later timepoints, especially for comorbidity outcomes. All patients were included who underwent surgery until the end of the six-year study period to aid analysis at shorter time intervals. However, this contributed to the diminishing sample sizes over time.

Conclusion

MBS resulted in satisfactory weight loss and sustained improvement in metabolic comorbidities in the majority of patients in this young Emirati population. Those who underwent RYGB appeared to lose more weight than those who underwent SG. Weight loss was in line with the international average for both procedures at one year, but patients responded less well five years after SG, consistent with a greater degree of weight recurrence. A novel finding was that women lost less weight than men after SG. T2D remission was more likely after RYGB than after SG, and the remission rate compared well with international studies up to five years after SG. The proportion of patients achieving remission from hyperlipidemia was greater for RYGB than for SG but not for those with hypertension. In an environment where RYGB may still be viewed with a degree of relative suspicion, this study supports stronger clinical recommendation in selected patients for RYGB over SG, especially for patients with T2D and hyperlipidemia. Prospective studies of our population are needed to investigate the reasons behind the reduced weight loss five years after SG and the difference in performance between sexes. This will enhance patient selection, allow for more targeted therapy and improve outcomes for women.

Acknowledgments

We would like to acknowledge Alia Al Tikriti who extracted the data for this work.

Disclosure

The authors report no conflicts of interest. No funding for the study was received.

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