Is Insulin Resistance at Baseline a Predictor of Weight Loss After Bariatric Surgery?

Background: Obesity is a multifactorial disease that is strongly associated to other metabolic disorders, such as insulin resistance and type 2 diabetes. Bariatric surgery is nowadays considered the most effective treatment of morbid obesity. The role of insulin resistance (IR) in weight loss after bariatric surgery is highly unknown. Aim: To evaluate the association between Insulin Resistance (IR) and percentage of excess weight loss (EWL%) one, two, three and four years after bariatric surgery in patients with morbid obesity. Methods: Retrospective longitudinal study in patients with morbid obesity followed in our centre between January 2010 and July 2018 were included. Patients were excluded if they had diabetes. We evaluated baseline Homeostatic Model Assessment of IR (HOMA-IR), Homeostatic Model Assessment of β-cell function (HOMA-beta), Quantitative Insulin Sensitivity Check Index (QUICKI) and Matsuda and DeFronzo index, and performed a linear regression concerning each year’s EWL%. Results: After applying the exclusion criteria, 1723 patients were included in this analysis. The logarithm of HOMA-beta was negatively associated with EWL% at second-, third- and fourth-years post-surgery (β=-1.04 [-1.82 to -0.26], p<0.01; β=-1.16 [-2.13 to -0.19], p=0.02; β=-1.29 [-2.64 to 0.06], p=0.061, respectively), adjusting for age, sex, body mass index and type of surgery. This was not observed in the first-year post-surgery nor for the other indexes. Glycaemia at baseline was also positively associated to EWL% at second- and third-years post-surgery. Conclusion: IR at baseline seems to be associated to long term weight loss, explicitly after the first year post bariatric surgery.