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Long-term benefit of short-term weight loss before bariatric surgery remains undetermined. This study assessed the relationship between percent total weight loss (%TWL) during a program-directed low-calorie diet (LCD) before primary bariatric surgery and long-term outcomes.


Patients from 2014-2019 who completed our program-directed 1200 kcal LCD for 4 weeks immediately before laparoscopic Roux-en-Y gastric bypass (LRYGB, n=572) or sleeve gastrectomy (LSG, n=484) were dichotomized to achievement (LRYGB n=220, LSG n=192) versus non-achievement (LRYGB n=352, LSG n=292) >=5% TWL during the diet. Primary endpoint was %TWL through 60 months post-operation. Secondary endpoints were operation time, length of stay (LOS), emergency department (ED) visits, intravenous fluid administration, readmission, reoperation. T-tests compared between group means with significance p<0.05.


Patients achieving >=5% TWL during the LCD experienced greater post-operation %TWL from month 1 to 60 for LRYRB and month 1 to 36 for LSG. Significant differences existed at 3 months (17.24+-3.29% vs 16.39+-3.36%, p=0.004) and 6 months (24.39+-4.76% vs 22.95+-5.04%, p=0.002) for LRYGB and at 3 months (15.62+-3.26% vs 14.15+-3.77%, p<0.001) through 18 months (22.60+-10.25% vs 18.68+-9.67%, p=0.028) for LSG. Mean LOS (LRYGB 1.75 days vs. 1.89, p=0.018; LSG 1.29 vs. 1.37, p=0.062) was lower for patients achieving >=5% TWL. ED visits (10.5% vs 5.8%, p=0.095) were greater for LSG patients achieving <5% TWL. No differences (p=NS) in other outcomes by weight loss group and surgery type transpired.


Achieving >=5% TWL during a program-directed 1200 kcal LCD for 4 weeks before bariatric surgery improves weight loss potential through 60 months post-operation.