Background: In the Netherlands, patients only qualify for bariatric surgery when they have followed a 6-month mandatory weight loss program (MWP), also called the "last resort" criterion. One of... Show moreBackground: In the Netherlands, patients only qualify for bariatric surgery when they have followed a 6-month mandatory weight loss program (MWP), also called the "last resort" criterion. One of the rationales for this is that MWPs result in greater weight loss.Objectives: To determine weight loss during MWPs and the effect of delayed versus immediate qualification on weight loss 3 years after bariatric surgery.Setting: Outpatient clinic.Methods: This is a nationwide, retrospective study with prospectively collected data. All patients who underwent a primary bariatric procedure in 2016 were included. We compared weight loss between patients who did not qualify according to the last resort criterion at screening (delayed group) with patients that qualified (immediate group).Results: In total 2628 patients were included. Mean age was 44.4 years, 81.3% were female, and baseline BMI was 42.3 kg/m(2). Roux-en-Y gastric bypass (RYGB) was the most frequently performed surgery (77.0%), followed by sleeve gastrectomy (15.8%) and banded RYGB (7.3%). The delayed group (n = 831; 32%) compared with immediate group (n = 1797; 68%), showed less percentage of total weight loss (%TWL) during the MWP (1.7% versus 3.9%, P < .001) and time between screening and surgery was longer (42.3 versus 17.5 wk, P < .001). Linear mixed model analysis showed no significant difference in %TWL at 18- (P = .291, n = 2077), 24- (P = .580, n = 1993) and 36-month (P = .325, n = 1743) follow-up.Conclusion: This study shows that delayed qualification for bariatric surgery compared with immediate qualification does not have a clinically relevant impact on postoperative weight loss 3 years after bariatric surgery. (C) 2020 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved. Show less