Validation of the Alterable Weight Loss Metric in Morbidly Obese Patients Undergoing Gastric Bypass in Korea

Abstract

Background: Percentage of excess weight loss (%EWL) is the most common metric used after bariatric surgery. However, there has been consistent argument against its use since it varies significantly by initial body mass index (BMI). This study aimed to validate the newly suggested percentage of alterable weight loss (%AWL) metric in Korean patients.

Methods: A retrospective review of the prospectively established database at Soonchunhyang University Seoul Hospital identified 165 patients who underwent primary laparoscopic Roux-en-Y gastric bypass (RYGB) and had at least 2-year follow-up weight loss results after surgery. Patients were classified into subgroups based on initial BMI, and their weight loss results expressed as BMI, %EWL, %AWL, and percentage of total weight loss (%TWL) were compared in terms of nadir weight and weight loss trajectory.

Results: The study cohort included 27 male (16.4%) and 138 female (83.6%) patients with a mean baseline BMI of 38.1 ± 5.4. Nadir weight was achieved at mean 24.1 ± 10.6 months postoperatively. Female patients required significantly longer to achieve nadir weight than male patients (16.2 vs. 22.4 months, p = 0.001), and they achieved less weight loss expressed as nadir BMI, %EWL, and %AWL. Of these metrics, only %AWL was not significantly influenced by preoperative BMI and showed the least variation (25.2%) for reporting weight loss.

Conclusion: The AWL metric can report weight loss regardless of baseline BMI in Korean patients undergoing RYGB; however, it must be validated in a larger population involving multiple centers from the Asia-Pacific area before being used clinically.

Keywords: Bariatric surgery; Body mass index; Gastric bypass; Weight loss.