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  • Published on: 15th October 2019
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The objective of this review of literature is to answer the following hypothesis: is gastric bypass surgery a viable option for weight loss to improve Diabetes Mellitus Type 2? Obesity has become a growing epidemic throughout the world, and gastric bypass surgery, specifically Roux-En-Y gastric bypass, has been become popular option to lose excess weight that can result in the remission of Diabetes Mellitus Type 2. Numerous studies, including the seven that are reviewed in this paper, have been performed in the hopes of finding a correlation between surgery and remission and an argument against current protocol utilized to achieve remission of Diabetes Mellitus Type 2. In conclusion, all seven studies showed an increase in remission rates amongst patients who underwent Roux-En-Y gastric bypass in comparison to those who utilized other interventions, such as medications and lifestyle changes.

  Background and Significance. Within the last few decades, obesity rates have been continuously rising, resulting in a worldwide medical epidemic (Kashyap et al., 2013). Obesity is defined as having a body mass index (BMI) of 30 or above or being greater than 20% of an individual’s ideal weight (Williams, 2017). Unfortunately, obesity is a major risk factor for the development of Diabetes Mellitus Type 2 (DMII) (Kashyap et al., 2013). Diabetes Mellitus Type 2 is the most commonly diagnosed form of diabetes with around 90% of patients being overweight, most likely due to uncontrolled weight gain (Williams, 2017). With this weight gain, the body is negatively affected, resulting in insulin resistance and/or impaired insulin secretion (“Facts about Type 2”, 2015).  Insulin resistance is described as the inability of cells to take up glucose to utilize as an energy source, and impaired insulin secretion is described as the pancreas’s inability to normalize blood glucose levels (“Facts about Type 2”, 2015). These two factors result in high blood glucose levels that can eventually lead to neuropathy, retinopathy, and/or nephropathy, if these levels are not addressed in a timely manner (Williams, 2017). Because of obesity’s effects on the body’s metabolism, the CDC performed a study to determine if there was a positive correlation between obesity and diagnosed diabetes. After recording an immense increase in obesity and diagnosed diabetes between 1994 and 2015, the CDC could confirm a positive correlation between the two factors (“Maps”, 2017). This confirmation led to the development and popularization of weight loss surgeries, including Roux-En-Y Gastric Bypass (RYGB), to remove excess weight and reverse the effects of Diabetes Mellitus Type 2. In RYGB, the stomach is stapled and separated into a large and small pouch. The small pouch becomes the “new stomach,” while the large pouch is removed from the body (Zieve, 2016). In addition to reducing the stomach to the size of a walnut, the jejunum is attached to the “new stomach,” causing the bypass of the duodenum. The end results are an inability to eat large portions, the ability to feel full with less food, and fewer calories absorbed (Zieve, 2016). Because of these results, RYGB has been noted to lead to higher DMII remission rates compared to nonsurgical medical intervention, which includes lifestyle changes such as exercise, diet, and medication. However, the current standard of care is to utilize a combination of medical therapy, which includes the usage of Metformin, lifestyle changes, and bariatric surgery; however, many believe that bariatric surgery should only be utilized by patients who are obese or morbidly obese when nonsurgical medical intervention has not been beneficial due to lack of compliance or other issues (Fernandez-Soto et al., 2017). Because of this current belief, many have asked the following question: is gastric bypass surgery a viable option for weight loss to improve Diabetes Mellitus Type 2? If RYGB can address the complications of Diabetes Mellitus Type 2, then patients will experience remission of their diabetes after surgical intervention.

  Analysis of Literature. Over the past few years, numerous studies have been performed with the goal of finding a correlation between Roux-En-Y gastric bypass and the remission of Diabetes Mellitus Type 2, including a study by Kashyap et al., which studied the effects of RYGB on the metabolism of moderately obese patients with DMII. The study was a randomized control trial that included 60 subjects that were separated into three treatment groups: medical therapy using medication, medical therapy with RYGB, and medical therapy with sleeve gastrectomy (Kashyap et al., 2013). Patients were then assessed at 12 and 24 months by body composition measurements and a liquid mixed-meal tolerance test, which was used to observe glucose tolerance, insulin sensitivity, and the secretion of insulin. Fasting blood samples were taken, and blood was drawn for the next 30 minutes for 2 hours after receiving the liquid mixed meal; diabetes medications were withheld for 24 hours (Kashyap et al., 2013). Results were then assessed through an analytic determination via plasma insulin and C- peptide assays and calculations that determined insulin secretion rate. Results were also tested for statistical significance with Chi Squared, Fisher Exact Test (two-tailed), one-way ANOVA, Student t test, and Wilcoxon test (Kashyap et al., 2013). After analyzing the results, it was determined that more success with bariatric surgeries was present in comparison to medical therapy alone, and more success with RYGB was present in comparison to sleeve gastrectomy. This conclusion was determined by comparisons involving glycemic and cardiovascular control, body weight, body composition, adipokines, mixed-meal tolerance, insulin sensitivity, pancreatic function, and incretin response (Kashyap et al., 2013). Although these results are conducive to the previously stated hypothesis, the study was limited due to its inclusion of only women participants. As Diabetes Mellitus Type 2 affects both men and women, both sexes would need to be included in this study to reduce bias.

  Although studies using prospective data are beneficial in answering the hypothesis, retrospective data has as much significance in reaching a conclusion. In Yan et al.’s systematic review and meta-analysis of randomized controlled trials regarding the difference in results between RYGB and medical treatment in obese patients with Diabetes Mellitus Type 2, six different trials with a collective 410 patients who received either RYGB or medical therapy and follow ups from one year to five years were included and analyzed. These studies were collected through various databases: PubMed, Embase, Cochrane Database, and Cochrane Clinical Trials Registry (Yan et al., 2016). The end points that were analyzed were hemoglobin A1C (HbA1c), body mass index (BMI), fasting plasma glucose (FPG), serum lipid level, waist circumference, blood pressure, adverse events, and medication usage. Comparisons between end points were deemed statistically significant or insignificant with the use of odds ratio, confidence intervals, and P values (Yan et al., 2016). After analyzing the results, it was concluded that Diabetes Mellitus Type 2 remission rates were higher in Roux-En-Y gastric bypass patients than those who only received medical treatment. However, the study also presented with some limitations that could have led to skewed results (Yan et al, 2016). When searching for retrospective data, searches were limited to only English literature; in addition, only six studies were utilized. These six studies were all performed under different lab parameters with no blinding. Lastly, publication bias was listed by the study’s authors, stating that significant data is more likely to be published than those that did not present with positive data (Yan et al., 2016).

  Like Yan et al.’s study, Schauer et al. did a five-year comparison of surgery to medical therapy in the remission of Diabetes Mellitus Type 2; however, two forms of weight loss surgery were utilized: Roux-En-Y gastric bypass and sleeve gastrectomy. This randomized control study treated and followed 150 patients and compared the number of patients who reached an HbA1c of 6.0% or less with or without the utilization of medication (Schauer et al., 2017). These results were analyzed using the Chi squared test and Fisher’s exact test. After the last follow up and the analysis of all results, it was determined that more bariatric surgery patients reached the 6.0% or less HbA1c endpoint goal in comparison to those who received medical therapy only (Schauer et al., 2017). In addition, a higher number of patients in the RYGB group reached the 6.0% or less HbA1c endpoint in comparison to those who received sleeve gastrectomy. It was then concluded that surgical procedures here more effective in the remission of DMII than medical therapy. However, with a small sample size of 150 patients, a short duration of study, and the admitted inability to detect small significant differences between RYGB and sleeve gastrectomy, this study may have some bias towards surgical means, specifically RYGB (Schauer et al., 2017).

  Within two of the previous studies, two different bariatric procedures had been used: Roux-En-Y gastric bypass and sleeve gastrectomy. With Fernandez-Soto et al.’s prospective observational study, the two procedures were compared in the remission of Diabetes Mellitus Type 2. 49 participants were given either a malabsorptive (RYGB) or restrictive (sleeve gastrectomy), and after one year, different end points were compared between the two groups: blood glucose levels, HbA1c, lipid profile, hypoglycemic treatment, and excess BMI lost percentage (EBL %) (Fernandez-Soto et al., 2017). These results were statistically analyzed through means, standard deviations, one-way ANOVA, and P values. After analysis of the results, it was concluded that there were no significant differences between Roux-En-Y gastric bypass and sleeve gastrectomy (Fernandez-Soto et al., 2017). However, it was determined that both surgeries were highly efficient in the remission of Diabetes Mellitus Type 2. Although this study contradicts a previously stated study that deemed RYGB more effective than sleeve gastrectomy, it presented with some limitations, including a short duration of study (Fernandez-Soto et al., 2017). However, the biggest limitation of this study was the sample size and its separation into groups. With 49 patients, 37 were given a mixed surgery, while only 12 received a restrictive surgery; this imbalance could lead to skewed results.

  Although the United States has a large obese population, obesity is an epidemic that affects other countries as well, including China. In Mazidi et al.’s prospective observational study, Chinese patients are treated and observed to note the effects of RYGB on glucose homeostasis, insulin secretion, insulin sensitivity, and diabetes control. For this study, 152 patients, 81% with diagnosed Diabetes Mellitus Type 2, underwent Roux-En-Y gastric bypass, and they were monitored for the next three years (Mazidi et al., 2017). During the first year, patients attended a follow up visit every three months, where their blood glucose levels, insulin resistance, BMI, insulin sensitivity, and DMII remission were recorded and analyzed. Results at the end of the three-year study were subjected to statistical analysis using means, standard deviations, medians, variance, Kruskal-Wallis test, and univariate logistic regression models (Mazidi et al., 2017). The study showed that fasting blood glucose was reduced during all follow ups and continued to decrease as time passed. Overall, findings suggested that RYGB improves insulin sensitivity, blood glucose levels, insulin resistance, BMI, and remission of DMII (Mazidi et al., 2017). Although these results were conducive to the previously stated hypothesis, the results may have been skewed. Not all patients who were originally approved for this study were included in the results, specifically those who did not undergo RYGB due to not meeting the Chinese criteria for the operation (Mazidi et al., 2017). This study also used an HbA1c threshold as the definition of remission without concern of whether the patient was receiving medical treatment. In addition, the literature that was used did not offer a concise definition of diabetes remission (Mazidi et al., 2017).

  Like the Chinese Study, the effects of gastric bypass surgery on obesity and Diabetes Mellitus Type 2 were also observed in Fenger et al.’s prospective observational study. 1,189 patients were separated into three groups before undergoing Roux-En-Y gastric bypass: non-diabetics, diabetics who were defined by having an HbA1c above 48 mmol/mol, and diabetics who were below the HbA1c threshold but were receiving some type of diabetes treatment. Patients who were defined as diabetics via HbA1c were separated into two subgroups: those who converted to non-diabetics after surgery without medication and those who received medication (Fenger et al., 2016). After the procedure, the body mass indexes of all patients were compared, and the results were subjected to statistical analysis using the Kolmogorov-Smirnov two-sample test, which is a non-parametric test of two continuous variables that distinguishes the largest absolute difference between the two values. The results from this study showed that BMI was reduced in all groups, but results suggested that genetics had a large effect on basic metabolism, which could be negatively affected by diabetes and preceding obesity (Fenger et al., 2016). This resulted in some patients who had addressed their obesity via RYGB, but not all the defects caused by DMII were not addressed and eliminated. Although this study had a larger population sample than the previous studies, it still came with its own limitations (Fenger et al., 2016). Fenger et al. only treated and observed Caucasian patients; in addition, 71.5% of the sample were female, leading to an uneven sex distribution. However, the biggest limitation is that out of the 1,189, only 741 patients have full records available, which could lead to some bias in the given results (Fenger et al., 2016).

    The last study that was utilized was a randomized control trial by Ikramuddin et al. that assessed the effectiveness of adding Roux-En-Y gastric bypass to current lifestyle change and medical management plans in mildly to moderately obese patients with uncontrolled Diabetes Mellitus Type 2. In this study, 120 patients were placed in two separate groups: those who received RYGB in addition to their current treatment plan and those who did not receive RYGB in addition to their current treatment plan (Ikramuddin et al., 2016). At the end of the 36-month study period, both groups were compared based on their low-density lipoprotein (LDL) cholesterol, systolic blood pressure, and HbA1c. Results were analyzed for statistical significance using logistic regressions for dichotomous data, linear regressions for continuous data, means, and standard deviations (Ikramuddin et al., 2016). The results should that all three compared endpoints were met by 28% of the RYGB group, compared to the 9% of the non-surgical group. While none of the non-surgical group reached diabetes remission, 17% of the RYGB group reached full remission, with 19% of the same group reaching partial remission. In the end, the non-surgical group was also using more medications to control Diabetes Mellitus Type 2 effects in comparison to the RYGB patients (Ikramuddin et al., 2016). Although these results support the previously stated hypothesis, the study included some limitations. While the exclusion of males in this study results in biased results, the biggest issue is the location of this study (Ikramuddin et al., 2016). The study took place at three clinical sites within the United States and a clinical site in Taiwan. This could result in differences in equipment, surgeons, diet, and other laboratory parameters, which can result in some inconsistencies when analyzing the collected data (Ikramuddin et al., 2016).

  Conclusions and Impact. Although there is a limited amount of studies available exploring the possible correlation between Roux-En-Y gastric bypass and Diabetes Mellitus Type 2 remission, the studies that are available have shown positive results after utilizing surgery to address effects of DMII. In all the studies within this review, RYGB proved to be more effective than lifestyle changes and medical management. Although it can neither be confirmed nor denied that RYGB is more effective than sleeve gastrectomy, the contradicting studies by Kashyap et al. and Schauer et al. both concluded that RYGB was an effective course of action when attempting to achieve remission in DMII patients.  Although success rate is still generally low across all the studies, it has been consistently better than non-surgical options. In conclusion, present literature continuously supports the hypothesis that gastric bypass surgery is a viable option for weight loss to improve Diabetes Mellitus Type 2.

    The impact of these studies is not limited to improving quality of life in patients, but it also affects other aspects of health care, including insurance coverage. If Roux-En-Y gastric bypass becomes more popular, then the vetting process utilized to approve patients may become less strict, resulting in more patients being approved. This increased popularity can result in increased insurance coverage, which can lead to reduced obesity rates and consequential Diabetes Mellitus Type 2 diagnoses. In addition, RYGB can be used for prophylaxis. Currently, surgery is only used for those who are obese and morbidly obese. However, with increased popularity, this can result in RYGB being used as a preventative measure in pre-diabetic patients (Fernandez-Soto et al., 2017). However, the biggest impact RYGB can have is the reduced usage of medical intervention. Current studies have shown that those who underwent RYGB had less dependence on or complete independence from medications, such as Metformin and insulin (Fernandez-Soto et al., 2017). With the widespread impact that Roux-En-Y gastric bypass can have, the obesity epidemic can finally be adequately and efficiently addressed.

  Future Directions. Despite the information that has been collected about the effects of Roux-En-Y gastric bypass on the remission of Diabetes Mellitus Type 2, there is still a vast amount that health care professionals do not know, including the long-term effects of this procedure on remission and maintenance. Available studies are all shorter than five years, meaning that current knowledge is based on what would be considered short-term results, in comparison to the average lifespan of a human being (Mazidi et al., 2017). Because of this, it is imperative that several studies be done for a longer period to further assess the success of RYGB in the remission of DMII. To begin to understand the long-term effects of RYGB, a prospective cohort study should be performed for longer than five years. This study should have an equal sex distribution, and all patients must be treated in the same location using the same laboratory parameters. The goals of this study would include the following: solidify conclusions regarding the benefits of Roux-En-Y gastric bypass in Diabetes Mellitus Type 2 remission, expand on current knowledge of RYGB’s effects, and determine the long-term effects of RYGB. Although this study would require a large amount of resources, including time and money, the benefits and possibility of eradicating the obesity epidemic outweigh the costs.

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