Anonymized dataset.

Introduction
The aim was to first investigate the efficacy of a preoperative weight management program centered on orlistat, which is mechanistically similar to gastrointestinal bypass procedures in that it restricts dietary fat absorption, and then assess its impact on the results of one-anastomosis gastric bypass (OAGB).
Materials and methods
We retrospectively reviewed the clinical data of consecutive patients aged 20–65 years with a body mass index (BMI) ≥ 42.5 kg/m2 who underwent primary OAGB from 2014 to 2020. Eligible patients who adhered to a 10–14 day orlistat regimen as part of a 4–6-week diet/lifestyle modification plan preceding surgery were stratified into weight reduction (Group 1) and weight gain (Group 2) groups post treatment. The correlation between pre- and postoperative weight loss and perioperative outcomes was assessed.
Results
Of 62 eligible patients, 55 met the inclusion criteria and complied with treatment; 35 (64%) patients in Group 1 lost a median of 2.0 kg, and Group 2 had a median weight gain of 2.9 kg. Group 1 had a significantly higher initial BMI (48.9 kg/m2 vs. 44.6 kg/m2; p = 0.003), more females (54% vs. 25%) and a shorter operation time than Group 2 (107 min vs. 140 min; p = 0.109). There was no difference in the incidence of 30-day complications. Weight loss did not differ between the groups at 24 months.
Conclusion
Effective weight control through an orlistat-containing regimen benefitted two-thirds of patients who underwent OAGB; however, further weight loss was not observed at 2 years post-surgery.