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Gastric Bypass Surgery in Patients with Type 2 Diabetes

Jul 11, 2020
Editor: Steve Freed, R.PH., CDE

Author: Stephanie Anderson, PharmD Candidate 2021, Skaggs School of Pharmacy and Pharmaceutical Sciences

What are the pros and cons of bariatric surgery, and how do results affect renal and cardiovascular outcomes in people with type 2?

Obesity and type 2 diabetes (T2D) are growing epidemics, and both lead to significant microvascular and macrovascular complications. Damage from obesity and hyperglycemia can cause atherosclerotic disease, cardiac arrhythmias, heart failure, and renal dysfunction. Bariatric surgery is 20-fold safer than it was 20 years ago, and complication risks have reached an all-time low of 2-5% [1]. Therefore, earlier intervention may lower the incidence of cardiovascular and renal comorbidities and eliminate the need for later high-risk procedures. Effects of gastric bypass surgery, specifically for patients with type 2 diabetes, have been examined more closely in the articles discussed below.


Liakopoulos et al. performed a nationwide observational study in Sweden that looked at the long-term effects of gastric bypass (GBP) surgery in patients with obesity and type 2 diabetes [2]. The focus was on clinical benefits, early postoperative outcomes, and long-term adverse effects of Roux-en-Y gastric bypass surgery. The researchers matched 5,321 subjects with control patients who had not undergone bariatric surgery. A Cox regression model, adjusting for sex, age, BMI, and socioeconomic factors, was used to compare BGP subjects and controls. Reported incidence rates included all-cause mortality and an array of comorbid diseases and complications (e.g., cardiovascular disease, hyperglycemia, kidney disease, G.I. complications, etc.). Event rates for all-cause mortality were 72.9 and 142.1 per 10,000 person-years in the GBP and control groups.

Results showed that risks for all-cause mortality (HR 0.51) as well as CVD, acute myocardial infarction, and congestive heart failure are lower after undergoing GBP surgery. Other pros included a reduced risk of kidney disease, hyperglycemia, cancer, and leg amputations. However, there were also significant adverse effects associated with GBP among this population. Bariatric surgery put patients at higher risk of anemia and malnutrition (HRs 1.92 and 2.81) and increased the risk of hospitalization due to psychiatric disorders or alcohol abuse (HRs 1.33 and 2.90). Another con is that GBP surgery led to additional G.I. surgery in 17.6% of the study group. A notable strength is the nationwide coverage of this study, likely making the results widely generalizable. However, a significant limitation is that diagnoses were only captured during hospitalization, not during outpatient care, potentially underestimating postoperative outcomes.

Another recent study by Liakopoulos et al. specifically examined renal and cardiovascular (CV) outcomes after GBP surgery in people with obesity and type 2 diabetes across several renal function categories [3]. Severe obesity and diabetes significantly elevate the risk of renal disease and CVD, ultimately increasing mortality risk, which explains the focus on these specific categories. Renal outcomes used eGFR, albuminuria, and creatinine for assessment, and CV outcomes used diagnoses sorted into categories. The risk for severe renal disease or a 50% reduction in eGFR was 41% lower in patients with normal renal function and 60-63% lower in patients with eGFR <45 mL/min/1.73m2. Additionally, there was a lower risk for CVD and all-cause mortality in the GBP group with notable risk reductions for heart failure (HR 0.33) and CVD mortality (HR 0.36).

In summary, incidence rates of almost all renal disease, cardiovascular disease, and mortality outcomes are lower in patients with obesity and T2D who have undergone gastric bypass surgery compared to those who have not. Substantial weight loss is more strongly linked to lowering the risk of cardiorenal-related outcomes than to atherosclerotic disease [3]. These beneficial findings related to GBP surgery appear to be consistent across all degrees of renal function, making bariatric surgery a potential option for even more patients. Although there are many long-term benefits associated with bariatric surgery, it is also crucial to consider the adverse outcomes related to the intervention.

Practice Pearls:  

  • The improved safety profile of bariatric surgery over the past 20 years has helped make GBP a realistic option for patients with obesity and type 2 diabetes to control their disease and prevent additional comorbid conditions.
  • Long-term GBP complications such as malnutrition, anemia, and psychiatric disorders are important considerations during patient selection for this procedure. Long-term postoperative monitoring and support can also minimize complications. 
  • Patients with obesity and type 2 diabetes who have undergone GBP surgery show lower incidence rates of renal disease, CV disease, and all-cause mortality compared to matched controls who have not had bariatric surgery. 


  1. Aminian, Ali, and Steven E Nissen. “Success (but Unfinished) Story of Metabolic Surgery.” Diabetes care 43,6 (2020): 1175-1177. doi:10.2337/dci20-0006
  2. Liakopoulos, Vasileios et al. “Pros and cons of gastric bypass surgery in individuals with obesity and type 2 diabetes: nationwide, matched, observational cohort study.” BMJ open 9,1 e023882. 15 Jan. 2019, doi:10.1136/bmjopen-2018-023882
  3. Liakopoulos, Vasileios et al. “Renal and Cardiovascular Outcomes After Weight Loss FromGastric Bypass Surgery in Type 2 Diabetes: Cardiorenal Risk Reductions Exceed Atherosclerotic Benefits.“ Diabetes care 43,6 (2020): 1276-1284. doi:10.2337/dc19-1703 


Stephanie Anderson, PharmD Candidate 2021, Skaggs School of Pharmacy and Pharmaceutical Sciences  


See more about gastric bypass / bariatric surgery in type 2 diabetes in our Surgery center.