Bariatric surgery is the most effective treatment against obesity and its related comorbidities. Insulin resistance (IR) is strongly linked to obesity, and has been shown to decrease after bariatric surgery. However, the impact of preoperative IR on bariatric surgery success is unknown. In this study, we investigate the effect of preoperative IR on bariatric surgery outcomes.


We performed a retrospective study of 950 patients who underwent Roux-en-Y gastric bypass or sleeve gastrectomy at a single institution. Demographic and clinical data were collected preoperatively and at 3-, 6-, and 12-months postoperatively. The homeostasis model assessment (HOMA) was used as a surrogate marker of IR, where a score ≥ 2.5 signifies IR status. Data were analyzed using student’s t-test and multivariate regression analysis.


A total of 776 IR subjects and 174 insulin sensitive (IS) subjects were included. Males comprised 25.2% of IR subjects, but only 9.2% of IS subjects (P=0.000). Preoperatively, IR subjects had a significantly greater BMI (46.99 ± 8.32; P=0.000) and increased comorbidities, including type II diabetes mellitus (60.3%; P=0.000), hyperlipidemia (54.9%; P=0.007), and hypertension (40.6%; P=0.005). Serum hemoglobin A1C (6.41±1.34; P=0.000), triglycerides (148.85 ± 104.50; P=0.000), and CRP (9.91 ± 9.11; P=0.000) were significantly higher in IR subjects preoperatively, while HDL levels were lower (45.24 ± 12.99; P=0.001). At 12-months postoperatively, both IR and IS individuals showed significant improvements in these lab markers. However, hemoglobin A1C (5.60 ± 0.75; P=0.001) remained higher and HDL (56.26 ± 15.33; P=0.041) lower in IR individuals compared to there IS counterparts (A1C: 5.40 ± 0.39; HDL: 59.86 ± 16.60). IR subjects showed lower percent of excess weight loss at 3- and 6- months after surgery (P=0.005 and P=0.002, respectively); however, this effect was no longer significant after controlling for gender, age, type of surgery, and preoperative BMI. Resolution of diabetes, hyperlipidemia, and hypertension at 12-months postoperatively was similar between IR and IS individuals. Postoperative complication rates at 30-days, 90-days, and 1 year were also unaffected by preoperative IR status.


Despite the higher preoperative BMI and increased prevalence and severity of comorbidities prior to surgery, IR bariatric surgery patients showed remarkable weight loss and resolution of comorbidities similar to their IS counterparts.