Methods: Patients who underwent LFS at hospitals that participated in the National Surgical Quality Improvement Program database within the United States between 2005 and 2015. Outcomes included 30-day medical complications, surgical complications, and length of stay (LOS). We analyzed a total of 39,742 patients with the use of the International Classification of Disease, ninth revision codes. The patients were categorized in the following two groups: group 1, individuals with a history of massive weight loss within 6 months before LFS, and group 2, individuals without a history of massive weight loss before surgery. Massive weight loss was defined as loss of 10% of total body weight. Patients with a history of malignancy or chronic disease were excluded from the study. Patients in each group were randomly matched based on age, gender, sex, smoking status, and body mass index. Paired two-tailed Student t -tests were used to compare the outcomes. Results: Of the 39,742 patients identified, 129 (0.32%) met the criteria for inclusion in the weight loss group (WL group) and were successfully matched to individuals in the non-weight loss group (non-WL group). Compared with the non-WL group, the WL group had a significantly longer LOS (9.7 vs. 4.0 days, p <0.05), higher surgical site infections (SSIs) (8.0 vs. 3.0, p <0.05), increased number of blood transfusions (40.0 vs. 20.0, p <0.05), and greater deep vein thrombosis (DVTs) (5.0 and 0.00, p <0.05). Conclusions On a nationwide scale, rapid weight loss before LFS is associated with a higher rate of postoperative complications, including SSI and DVTs, longer average LOS, and more frequent blood transfusions.