Total Weight Loss As the Outcome Measure of Choice After Roux en-Y- Gastric Bypass

Mena Boules, MD1, Ricard Corcelles, MD, PhD2, Dvir Froylich, MD1, Amani Hag, MD1, Zhamak Khorgami, MD1, Bartolome Burguera, MD1, Matthew Kroh, MD1, Phillip Schauer, MD1, Stacy Brethauer, MD1. 1Cleveland Clinic, 2Foundation Clinic for Biomedical Research, Hospital Clinic of Barcelona, University of Barcelona

Background: Currently, there is no agreement on the best method to describe weight loss (WL) after bariatric surgery. The aim of this study is to evaluate short-term outcomes using percent of total body weight loss (%TWL).

Methods: A single-institution retrospective study of 2,420 patients undergoing Roux-en-Y gastric bypass (RYGB) was performed. Suboptimal WL was defined as %TWL < 20% at 12 months.

Results: Mean preoperative BMI was 46.8 ± 7.8 kg/m2. 12 months post-operatively, a mean reduction of 14.1 kg/m2 units of body mass index (BMI), 30.0 ± 8.5% TWL, and 68.5 ± 22.9% EWL. At 6 and 12 months post-RYGB, mean BMI and %EWL significantly improved for all 60 baseline BMI groups (p<0.01, BMI; p=0.01, %EWL), whereas mean %TWL was not significantly different among baseline BMI groups (p=0.9). The regression analysis between each metric outcome and preoperative BMI demonstrated that preoperative BMI did not significantly correlate with %TWL at 1 year (r=0.04, p=0.3). On the contrary, pre-operative BMI was strongly but negatively associated with the %EWL (r=-0.52,65 p<0.01) and positively associated with the BMI units lost at 1 year (r=0.56, p<0.01). In total, 11.3% of subjects achieved <20 %TWL at 12 months and were considered as suboptimal WL patients.

Conclusion: The results of our study confirm that %TWL is a compelling metric when reporting WL due to less likelihood of being influenced by pre-operative BMI. Importantly, 11% of patients displayed sub-optimal  WL during the in the first year after RYGB based on our definition.

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