The effects of bariatric surgery on dyslipidemia and insulin resistance in overweight patients with or without type 2 diabetes: a systematic review and network meta-analysis

Bariatric Surgery and Remission of Metabolic Syndrome: A Meta-analysis of Randomised Controlled Trials and Prospective Studies

BACKGROUND

Studies have discussed the efficacy of bariatric surgery (BS) in remission of individual components of metabolic syndrome (MS). We aimed to analyse the prevalence of MS following BS.

METHODS

On October 5, 2023, we conducted a literature search on PubMed, Scopus, Web of Science, and Cochrane. RevManv5.4 was used for the analysis.

RESULTS

MS patients who underwent BS had lower odds of MS within the first year post-BS (OR 0.14, 95%CI 0.12-0.17); patients who had a preoperative BMI < 50 showed a higher reduction in MS post-BS compared with patients who suffered from super obesity (OR 0.12 versus OR 0.17). Older patients (age > 42) had lower odds of MS post-BS compared with younger patients (OR 0.05 versus OR 0.17). There was not a difference in MS prevalence between 1 and 2 years postoperatively (OR 1.07, 95%CI 0.72-1.58). Asians reported the highest reduction in MS post-BS (OR 0.08). MS patients who received medical treatment had three times the odds of having MS compared with patients who underwent BS. Patients who had BS reported a decline in their anti-hypertensives and oral anti-diabetic drugs (OR 0.26, 95%CI 0.15-0.46, OR 0.11, 95%CI 0.07-0.16, respectively). There was not a significant difference in MS prevalence between patients who underwent RYGB and those who had SG (OR 2.16, 95%CI 0.74-6.26).

CONCLUSIONS

BS is superior to medical treatment in the remission of MS. Age, preoperative BMI, and country of origin affect the rates of MS remission. BS results in a sustainable resolution of MS across 1, 2, and 5 years post-surgery. A tailored approach is warranted to achieve the best outcomes.

Sleeve Gastrectomy and Its Impact on Insulin Resistance and Metabolic Health: A Cohort Study

BACKGROUND

Obesity is a prevalent metabolic disorder that significantly contributes to insulin resistance (IR), type 2 diabetes (T2DM), and metabolic syndrome. Sleeve gastrectomy has emerged as an effective surgical intervention for obesity, with potential benefits on metabolic health. This study investigates the impact of sleeve gastrectomy on serum insulin levels, IR (HOMA-IR), inflammatory markers, C-peptide, kidney function, and various biochemical parameters in diabetic and non-diabetic patients.

METHODS

A prospective cohort study was conducted, involving 199 patients over 18 years old who were candidates for sleeve gastrectomy at Luqman Hakim Hospital from 2021 to 2022. Data were collected using standardized questionnaires and anthropometric measurements, and biochemical assessments were performed before surgery and 6 months postoperatively. Statistical analyses included descriptive statistics, t-tests, Mann-Whitney tests, and repeated measures analysis of variances (ANOVA).

RESULTS

The study included 199 patients (84.4% female) with a mean (± standard deviation (SD)) age of 39.79 ± 11.30 years. Significant reductions were observed in weight, BMI, and abdominal circumference across all patient groups. Diabetic patients showed marked improvements in fasting blood sugar, 2-h postprandial blood sugar, and glycosylated hemoglobin levels. Insulin resistance decreased significantly, as did serum insulin and C-peptide levels. Improvements in lipid profiles and inflammatory markers were also noted. Insulin use post-surgery showed a significant inverse relationship with glycemic control improvement.

CONCLUSIONS

Sleeve gastrectomy is a safe and effective procedure for obese patients, significantly improving insulin resistance and various obesity-associated diseases within 6 months post-surgery.

Integrated Insights into Metabolic and Bariatric Surgery: Improving Life Quality and Reducing Mortality in Obesity

Metabolic and bariatric surgery (MBS) is an effective intervention for patients with severe obesity and metabolic comorbidities, particularly when non-surgical weight loss methods prove insufficient. MBS has shown significant potential for improving quality of life and metabolic health outcomes in individuals with obesity, yet it carries inherent risks. Although these procedures offer a multifaceted approach to obesity treatment and its clinical advantages are well-documented, the limited understanding of its long-term outcomes and the role of multidisciplinary care pose challenges. With an emphasis on quality-of-life enhancements and the handling of postoperative difficulties, the present narrative review seeks to compile the most recent findings on MBS while emphasizing the value of an integrated approach to maximize patient outcomes. Effective MBS and patients' management require a collaborative team approach, involving surgeons, dietitians, psychologists, pharmacists, and other healthcare providers to address not only physiological but also psychosocial patient needs. Comparative studies demonstrate the efficacy of various MBS methods, including Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy that may considerably decrease morbidity and mortality in individuals with obesity. Future studies should target long-term patient treatment, and decision making should be aided by knowledge of obesity, comorbidity recurrence rates, and permanence of benefits.

Impact of metabolic bariatric surgery on outcomes and the 10-year risk of major adverse cardiovascular events during a 7-year period: a retrospective cohort study

BACKGROUND

Metabolic bariatric surgery offers enduring weight reduction and alleviation of obesity-related comorbidities, including dyslipidemia, diabetes, hypertension, and major adverse cardiovascular events (MACE). Long-term data on one-anastomosis gastric bypass (OAGB) and single-anastomosis duodenal-jejunal bypass with sleeve gastrectomy (SADJB-SG) is lacking, necessitating this investigation.

MATERIALS AND METHODS

In this multicenter prospectively-collected retrospective observational study, 830 adult Taiwanese patients (682 OAGB, 148 SADJB-SG) who underwent surgery from 1 January 2011 to 31 December 2017, were initially identified. Following protocol, 224 patients (177 OAGB, 47 SADJB-SG) with complete follow-up data at various intervals up to 3 years after surgery were included in the final analysis. The study's primary focus is to evaluate the long-term safety, efficacy, and durability of OAGB and SADJB-SG in promoting weight loss and diabetes remission. Additionally, changes in 10-year and lifetime risks of MACE before and 3-year after surgery are assessed using Taiwan MACE risk prediction model and the China-PAR project model.

RESULTS

SADJB-SG patients exhibit higher diabetes prevalence, lower BMI, and more severe diabetes compared to OAGB. Both groups demonstrate significant improvements in BMI, diabetes, hypertension, and dyslipidemia three years after surgery, with the most substantial improvements occurring in the second year. The Taiwan MACE risk model reveals a significant reduction in 10-year MACE and stroke risks for both groups. The China-PAR project model indicates a synchronized reduction in atherosclerotic cardiovascular disease 10-year and lifetime risk in both OAGB and SADJB-SG groups.

CONCLUSIONS

OAGB and SADJB-SG exhibit sustained improvements in weight reduction and obesity-related comorbidities over 3 years after surgery. Notably, both procedures contribute to a substantial reduction in 10-year MACE, stroke, and atherosclerotic cardiovascular disease risks. These findings underscore the efficacy of OAGB and SADJB-SG in the context of metabolic bariatric surgery.

Long-term systemic effects of metabolic bariatric surgery: A multidisciplinary perspective

Background

Obesity is a global health crisis with profound implications on various body systems, contributing to a series of comorbidities. Metabolic Bariatric Surgery (MBS) has emerged as an effective treatment option for severe obesity, with significant weight reduction and potential systemic physiological alterations.

Objectives

This narrative review aims to provide a comprehensive analysis of the long-term effects of MBS on a wide array of body systems, including the heart, liver, kidneys, reproductive system, skin, lungs, digestive tract, pancreas, and blood, as well as related cancers of these organs.

Methods

A systematic search was conducted in academic databases (PubMed, ISI Web of Science, and Scopus) for observational studies and reviews published between July 2000 and December 2023, investigating the association between MBS and the subsequent function of different organ systems. High-quality studies were prioritized to ensure reliable evidence synthesis.

Results

MBS has demonstrated favorable outcomes in reducing cardiovascular disease risk, improving cardiac function, and alleviating heart failure symptoms. It has also been associated with improved respiratory function, remission of obstructive sleep apnea, and reduced cancer incidence and mortality. Additionally, MBS has shown benefits in managing gastrointestinal disorders, enhancing glycemic control, and promoting pancreatic beta-cell regeneration in type 2 diabetes mellitus. However, some methods of MBS are associated with a higher risk of cholelithiasis, GERD, and pancreatic exocrine insufficiency.

Conclusion

MBS has far-reaching systemic effects beyond weight loss, offering potential long-term benefits for various organ systems and comorbidities associated with obesity. For many patients with severe obesity, the potential benefits of Metabolic and Bariatric Surgery (MBS) can outweigh the associated risks. However, careful evaluation by a qualified healthcare professional is crucial to determine candidacy and ensure a successful outcome. Further research is needed to fully elucidate the long-term impacts and tailor personalized treatment approaches.

Randomized controlled trials comparing gastric bypass, gastric band, and sleeve gastrectomy: A systematic review examining validity and applicability to wider clinical practice

Consideration of how applicable the results of surgical trials are to clinical practice is important to inform decision-making. Randomized controlled trials comparing at least two surgical interventions (of gastric bypass, gastric band, and sleeve gastrectomy) for severe and complex obesity were examined using the PRagmatic Explanatory Continuum Indicator Summary-2 tool, to consider how applicable the trial results are to clinical practice, and the Risk of Bias 2 tool, to examine validity. MEDLINE, Embase, and CENTRAL databases were searched for studies published between November 2013 and June 2021, and 15 were identified. Using the PRagmatic Explanatory Continuum Indicator Summary-2 tool, three were classified as pragmatic, with good applicability to clinical practice. Ten had more explanatory domains but did include some pragmatic characteristics, and two were predominantly explanatory. This was due to some trial design features that would not be considered applicable to the wider clinical setting, including being single-centered, having prescribed intervention delivery methods, and intensive follow-up regimens. Only two trials had low risk of bias, of which one was considered pragmatic. Three had high risk of bias. Overall, few trials in bariatric surgery are pragmatic with low risk of bias. Well-designed pragmatic trials are needed to inform practice and reduce research waste.

Bariatric Surgery Improves Cognition Function in the Patients with Obesity: A Meta-Analysis

Obesity and related comorbidities have negative impacts on cognitive function. Weight loss seems to be associated with the improvement of cognitive function and the recovery of brain structure, but the underlying mechanism is not clear. This meta-analysis aimed to explore the status of cognitive function including memory, executive function, attention and language ability in patients with obesity, and to further investigate whether bariatric surgery can improve overall cognitive function in these patients. A total of 11 literatures with 728 subjects were included after retrieval and exclusion. The meta-analysis showed significant improvements in memory, attention and executive function scores after undergoing bariatric surgery in the patients with obesity. However, there was no significant improvement in language ability.

Benefits of metabolic surgery on macrovascular outcomes in adult patients with type 2 diabetes: a systematic review and meta-analysis

Type 2 diabetes (T2D) is a chronic metabolic disorder that affects millions of individuals associated with an increased risk of mortality and macrovascular complications. We aimed to synthesize the benefit of metabolic surgery (MS) on macrovascular outcomes in adult patients with T2D.We included both cohort studies and randomized controlled trials (RCTs) that evaluated MS added to medical therapy compared with medical therapy alone in the treatment of adult patients with T2D. Studies must have evaluated the incidence of any macrovascular complication of the disease for a period of at least 6 months. We performed our search using PubMed, Scopus, EMBASE, Web of Science, and COCHRANE Central database which was performed from inception date until March 2022. The trial protocol was previously registered at PROSPERO (CRD42021243739). A total of 6338 references were screened throughout the selection process from which 16 studies involving 179,246 participants fulfilled inclusion criteria. MS reduced the risk of any cardiovascular event by 44% (relative risk .56 [95% CI, .42-.75]; P = < .001), myocardial infarction by 54% (.46 [95% CI, .26-.83]; P = .009), coronary artery disease by 40% (.60 [95% CI, .42-.85]; P = .004) and heart failure by 71% (.29 [95% CI, .14-.61]; P = .001). It also provided a risk reduction of stroke by 29% (.71 [95% CI, .51-.99]; P = .04) and 38% (.62 [95% CI, .46-.85]; P = .001) for cerebrovascular events. On mortality, MS yields a risk reduction of 55% (.45 [95% CI, .36-.57]; P <.001) in overall mortality and 69% in cardiovascular mortality (relative risk .31 [95% CI, .22-.42]; P < .001). Peripheral vascular disease risk was also reduced. MS in adult patients with T2D can reduce the risk of mortality and of any macrovascular outcomes. However, there is a need for the planning of randomized clinical trials to further analyze and confirm the results.

Bariatric Surgery and Risk of Hospitalization for Gastrointestinal Cancers in the USA: a Propensity Score Matched Analysis of National Inpatient Sample Study

BACKGROUND

There are some concerns about the higher risk of certain gastrointestinal (GI) cancers in patients with a history of bariatric metabolic surgery (BMS). The current study aimed to investigate the association of BMS with GI cancer hospital admission including esophageal, gastric, colorectal, small intestinal, liver, gallbladder, bile duct, and pancreatic cancers.

METHODS

The analysis utilized the US national inpatient sample (NIS) data from 2016 to 2020, employing ICD-10 codes. A propensity score matching in a 3:1 ratio was done to match the BMS and non-BMS groups.

RESULTS

A total of 328,369 patients with a history of BMS and 4,989,154 with obesity and without a history of BMS were included in this study. BMS was independently associated with a higher risk of gastric and pancreatic cancers hospital admission (OR: 1.69 (CI 95%: 1.42-2.01) and OR: 1.46 (CI 95%: 1.27-1.68)), respectively. In addition, BMS was independently associated with a lower risk of colorectal and liver cancer hospital admission (OR: 0.57 (CI 95%: 0.52-0.62) and OR: 0.72 (CI 95%: 0.52-0.98)), respectively. Besides, esophageal, gallbladder, bile duct, and small intestinal cancer were not significantly different between the two groups. In patients with GI cancer, although the BMS group had significantly lower total charges and length of hospital stay compared to the non-BMS group, the rate of in-hospital mortality was not significantly different.

CONCLUSION

The current study showed that bariatric surgery may be associated with a higher risk of gastric and pancreatic cancer and a lower risk of colorectal and liver cancer hospital admission. Further research is needed to explore this association.

The impact of maternal bariatric surgery on long-term health of offspring: a scoping review

While pregnancy post-bariatric surgery has become increasingly common, little is known about whether and how maternal bariatric surgery affects the next generation. This scoping review aimed to collate available evidence about the long-term health of offspring following maternal bariatric surgery. A literature search was conducted using three databases (PubMed, PsycINFO, EMBASE) to obtain relevant human and animal studies. A total of 26 studies were included: 17 were ancillary reports from five "primary" studies (three human, two animal studies) and the remaining nine were "independent" studies (eight human, one animal studies). The human studies adopted sibling-comparison, case-control, and single-group descriptive designs. Despite limited data and inconsistent results across studies, findings suggested that maternal bariatric surgery appeared to (1) modify epigenetics (especially genes involved in immune, glucose, and obesity regulation); (2) alter weight status (unclear direction of alteration); (3) impair cardiometabolic, immune, inflammatory, and appetite regulation markers (primarily based on animal studies); and (4) not affect the neurodevelopment in offspring. In conclusion, this review supports that maternal bariatric surgery has an effect on the health of offspring. However, the scarcity of studies and heterogenous findings highlight that more research is required to determine the scope and degree of such effects. IMPACT: There is evidence that bariatric surgery modifies epigenetics in offspring, especially genes involved in immune, glucose, and obesity regulation. Bariatric surgery appears to alter weight status in offspring, although the direction of alteration is unclear. There is preliminary evidence that bariatric surgery impairs offspring's cardiometabolic, immune, inflammatory, and appetite regulation markers. Therefore, extra care may be needed to ensure optimal growth in children born to mothers with previous bariatric surgery.

Diabetic Markers, Five Years after Bariatric Surgery

Background: Bariatric surgery delivers substantial weight loss for obese patients with comorbidities like diabetes mellitus. We aimed to investigate the impacts of bariatric surgery on diabetic markers after 5 years of follow-up. Methods: This is a retrospective study on patients with diabetes and a history of bariatric surgery between 2016-2017. The diabetic markers before and 5 years following surgery, including a lipid profile, glucose level, and the required antidiabetic medications, were evaluated. Results: 34 consecutive patients were included, 30 (88.2%) women, with a mean age of 52.71±8.53 years. The majority (65%) of surgeries were Roux-en-Y gastric bypass (RYGB), and the remaining were one anastomosis gastric bypass (OAGB) and sleeve gastrectomy (SG). The serum levels of diabetic markers reduced during follow-up (P=0.001), except for high-density lipoprotein levels and serum total cholesterol, which increased (P=0.011, P=0.838). Low-density lipoprotein levels reduced, but it was insignificant (P=0.194). Surgery types had affected the changes of diabetic markers (P>0.05). Demand for oral medication was reduced significantly, but insulin injection reduction was not significant (P=0.006 and P=0.099, respectively). Conclusion: Our study showed favorable bariatric surgery results on patients with diabetes in long-term follow-up. However, dyslipidemia is still a concern.

The role of glucagon after bariatric/metabolic surgery: much more than an "anti-insulin" hormone

The biological activity of glucagon has recently been proposed to both stimulate hepatic glucose production and also include a paradoxical insulinotropic effect, which could suggest a new role of glucagon in the pathophysiology type 2 diabetes mellitus (T2DM). An insulinotropic role of glucagon has been observed after bariatric/metabolic surgery that is mediated through the GLP-1 receptor on pancreatic beta cells. This effect appears to be modulated by other members of the proglucagon family, playing a key role in the beneficial effects and complications of bariatric/metabolic surgery. Glucagon serves a dual role after sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). In addition to maintaining blood glucose levels, glucagon exhibits an insulinotropic effect, suggesting that glucagon has a more complex function than simply an "anti-insulin hormone".

Benefits of bariatric surgery on microvascular outcomes in adult patients with type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Microvascular diabetes complications impair patients' health-related quality of life. Bariatric surgery (BS) emerged as a compelling treatment that demonstrated to have beneficial effects on patients with diabetes and obesity.

OBJECTIVE

We aimed to synthesize the benefit of bariatric surgery on microvascular outcomes in adult patients with type 2 diabetes.

SETTING

2011-2021.

METHODS

We included both cohort studies and randomized trials that evaluated bariatric surgery added to medical therapy compared with medical therapy alone in the treatment of adult patients with type 2 diabetes. Studies must have evaluated the incidence of any microvascular complication of the disease for a period of at least 6 months. We performed our search using PubMed, Scopus, EMBASE, Web of Science, and COCHRANE Central database which was performed from inception date until March 2021. PROSPERO (CRD42021243739).

RESULTS

A total of 25 studies (160,072 participants) were included. Pooled analysis revealed bariatric surgery to reduce the incidence of any stage of retinopathy by 71% (odds ratio [OR] .29; 95% confidence interval [CI] .10-.91), nephropathy incidence by 59% (OR .41; 95% CI 17-96), and hemodialysis/end-stage renal disease by 69% (OR .31 95% CI .20-.48). Neuropathy incidence revealed no difference between groups (OR .11; 95% CI .01-1.37). Bariatric surgery increased the odds of albuminuria regression by 15.15 (95% CI 5.96-38.52); higher odds of retinopathy regression were not observed (OR 3.73; 95% CI .29-47.71). There were no statistically significant differences between groups regarding the change in surrogate outcomes.

CONCLUSIONS

Bariatric surgery in adult patients with diabetes reduced the odds of any stage of retinopathy, hemodialysis/end-stage renal disease, and nephropathy composite outcome. However, its effect on many individual outcomes, both surrogates, and clinically significant, remains uncertain.

Hypertension and hypercholesterolemia are predictive factors associated with type 2 diabetes persistence after metabolic surgery: A prospective study

BACKGROUND

Metabolic surgery is the most effective therapeutic strategy for the management of type 2 diabetes (T2DM). Several preoperative clinical factors have been associated with T2DM remission after metabolic surgery. However, other potential predictors remain unexplored.

AIM

To assess the role of basal (pre-surgery) clinical and biochemical parameters in T2DM remission after metabolic surgery.

METHODS

A prospective study including 98 patients with T2DM undergoing metabolic surgery was performed. Clinical, anthropometric, and biochemical data were collected at baseline and 1 year following metabolic surgery.

RESULTS

Patients without T2DM remission 1 year after metabolic surgery presented a longer duration of diabetes and higher glycated hemoglobin (HbA1c) levels; a higher percentage of these subjects were using insulin therapy, antihypertensive drugs, and lipid-lowering therapies before metabolic surgery, compared to those patients with T2DM remission. A lower percentage of T2DM remission after metabolic surgery was observed among patients with hypertension/hypercholesterolemia before surgery, compared to those patients without hypertension/hypercholesterolemia (51.7 % vs 86.8 %, p < 0.001, and 38.5 % vs 75 %, p < 0.001, respectively), and among patients with longer duration of diabetes (≥5 years vs <5 years; 44.4 % vs 83 %, respectively; p < 0.001). In the logistic regression model, diabetes duration, basal HbA1c, and the presence of hypertension and hypercholesterolemia before surgery were inversely related to T2DM remission following metabolic surgery, after adjusting for sex, age, waist circumference, and type of surgery.

CONCLUSIONS

In a cohort of patients with obesity and T2DM, preoperative hypertension and hypercholesterolemia, together with a longer diabetes duration and higher HbA1c concentrations, were independent predictors of T2DM persistence after metabolic surgery.

Differential Gene Expression of Subcutaneous Adipose Tissue among Lean, Obese, and after RYGB (Different Timepoints): Systematic Review and Analysis

The main roles of adipose tissue include triglycerides storage and adipokine secretion, which regulate energy balance and inflammation status. In obesity, adipocyte dysfunction leads to proinflammatory cytokine production and insulin resistance. Bariatric surgery is the most effective treatment for obesity, the gold-standard technique being Roux-en-Y gastric bypass (RYGB). Since metabolic improvements after RYGB are clear, a better understanding of adipose tissue molecular modifications could be derived from this study. Thus, the aim of this systematic review was to find differentially expressed genes in subcutaneous adipose tissue of lean, obese and post-RYGB (distinct timepoints). To address this objective, publications from 2015-2022 reporting gene expression (candidate genes or transcriptomic approach) of subcutaneous adipose tissue from lean and obese individuals before and after RGYB were searched in PubMed, Elsevier, and Springer Link. Excluded publications were reviews, studies analyzing serum, other types of tissues, or bariatric procedures. A risk-of-bias summary was created for each paper using Robvis, to finally include 17 studies. Differentially expressed genes in post-RYGB vs. obese and lean vs. obese were obtained and the intersection among these groups was used for analysis and gene classification by metabolic pathway. Results showed that the lean state as well as the post-RYGB is similar in terms of increased expression of insulin-sensitizing molecules, inducing lipogenesis over lipolysis and downregulating leukocyte activation, cytokine production and other factors that promote inflammation. Thus, massive weight loss and metabolic improvements after RYGB are accompanied by gene expression modifications reverting the "adipocyte dysfunction" phenomenon observed in obesity conditions.

The Effect of Bariatric Surgery on Circulating Levels of Lipoprotein (a): A Meta-analysis

BACKGROUND

Obesity, especially severe obesity, is associated with a higher risk of atherosclerotic cardiovascular disease (ASCVD) morbidity and mortality. Bariatric surgery is a durable and effective weight loss therapy for patients with severe obesity and weight-related comorbidities. Elevated plasma levels of lipoprotein (a) (Lp(a)) are causally associated with ASCVD. The aim of this meta-analysis was to analyze whether bariatric surgery is associated with Lp(a) concentrations.

METHODS

A literature search in PubMed, Scopus, Embase, and Web of Science was performed from inception to May 1st, 2021. A random-effects model and the generic inverse variance weighting method were used to compensate for the heterogeneity of studies in terms of study design, treatment duration, and the characteristics of the studied populations. A random-effects metaregression model was used to explore the association with an estimated effect size. Evaluation of funnel plot, Begg's rank correlation, and Egger's weighted regression tests were used to assess the presence of publication bias in the meta-analysis.

RESULTS

Meta-analysis of 13 studies including 1551 patients showed a significant decrease of circulating Lp(a) after bariatric surgery (SMD: -0.438, 95% CI: -0.702, -0.174, p < 0.001, I 2: 94.05%). The results of the metaregression did not indicate any significant association between the changes in Lp(a) and duration of follow-up after surgery, reduction in body mass index, or baseline Lp(a) concentration. The reduction in circulating Lp(a) was robust in the leave-one-out sensitivity analysis.

CONCLUSION

Bariatric surgery significantly decreases circulating Lp(a) concentrations. This decrease may have a positive effect on ASCVD in obese patients.