Impact of Preoperative Weight Loss on Postoperative Weight Loss Revealed from a Large Nationwide Quality Registry.

PURPOSE: Weight loss before bariatric surgery is not mandatory, but questions remain as to whether preoperative weight loss has an impact on weight loss after surgery. Most studies have small sample sizes. The objective was to evaluate the relationship between preoperative and successful postoperative weight loss defined as ≥25% total weight loss (TWL) at 1 and 2 years after primary bariatric surgery with regard to the obesity-related comorbidities. MATERIALS AND METHODS: Data were extracted from a large nationwide quality registry of patients who underwent a sleeve gastrectomy (SG) or gastric bypass (GBP) between January 2015 and January 2018. Patients with completed screening and preoperative and postoperative data were included. A multivariate logistic regression analysis was performed for each technique and follow-up years separately. RESULTS: In total, 8751 were included in the analysis. Patients with preoperative weight loss were more likely to achieve ≥25% postoperative TWL in both procedures. Patients with higher preoperative weight loss of 5-10% had an increased likelihood for achieving 25% TWL compared to 0-5%, OR 1.79 (CI (1.42-2.25), p < 0.001) vs 1.25 (CI (1.08-1.46), p < 0.004) for the GBP group for year 2 postoperative. This was the same for the SG group at year 2, OR 1.30 (CI (1.03-1.64), p < 0.029) vs 1.14 (CI (0.94-1.38), p < 0.198). CONCLUSION: Patients with preoperative weight loss were more likely to achieve ≥25% postoperative TWL at 1 and 2 years after surgery in both procedures; moreover, the extent of preoperative weight loss contributes to the significance and odds of this success.