Objective: Participating in a weight loss program before bariatric surgery is an established preparation tool in many specialized bariatric clinics. A certain amount of weight loss before surgery can even be a mandatory requirement for some clinics or insurance companies. The objective of this study is to investigate whether successful preoperative weight loss through adherence to a low-calorie diet three weeks prior to bariatric surgery could predict a difference in the duration of the procedure, intraoperative blood loss, need for revision, excess weight loss after 12 months and the participation in postoperative follow-up visits.

Methods: All cases that underwent sleeve gastrostomy or Roux-en-Y gastric bypass in a bariatric department in Germany between January 2018 and October 2019 were retrospectively evaluated for our study. Data were obtained on gender, age, BMI, weight before and after preoperative weight loss, weight after 1, 3, 6, and 12 months, operative times, haemoglobin and haematocrit one day before and two days after surgery, the need for revision 4 weeks after the procedure, and the number of follow-up visits. Groups were formed according to the achieved excess weight loss before surgery and analysed inter alia using Kruskal Wallis H Test

Results: The study included 201 patients. Both, patients that underwent sleeve gastrostomy (n=66) or Roux-en-Y gastric bypass (n=135), participated significantly more often in follow-up visits (P = 0.004 and P = 0.012), if they lost a higher amount of excess weight prior to surgery compared to patients that lost less. Patients that underwent Rouxen- Y gastric bypass also showed higher adherence to follow-up visits than patients that underwent sleeve gastrostomy. Blood loss, operative times, need for revision and weight loss after one year did not differ between groups that lost a high, medium, or low amount of excess weight preoperatively.

Conclusions: Preoperative weight loss showed to be a good predictor of follow-up adherence after bariatric surgery. As adherence and participation in regular follow-up visits appear to be crucial for the long-term success of bariatric interventions, the possible prediction of patient adherence is set to increasingly gain importance.