Comparison between total weight loss and other metrics after bariatric surgery using a multilevel mixed-effects linear regression model.

Background: Several tools are used to assess postoperative weight loss after bariatric surgery, including the percentage of excess body weight loss (%EWL), percentage of total weight loss (%TWL), and percentage of excess body mass index (BMI) loss (%EBMIL). A repeated series of measurements should be considered to assess weight loss as accurately as possible. This study aimed to test weight loss metrics.

Methods: Data were obtained from a prospective database of patients with obesity who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB) or laparoscopic sleeve gastrectomy (LSG) between 2016 and 2017 in a French tertiary referral bariatric center. A multilevel mixed-effects linear regression model with repeated measures was used to analyze repeated weight measurements over time.

Results: A total of 435 patients underwent LRYGB (n = 266) or LSG (n = 169). At 2 years, the average %EWL, %EBMIL, and %TWL were 56.8%, 61.3%, and 26.6%, respectively. Patients who underwent LSG experienced lower weight loss (β: - 4233 in %TWL model, β: - 6437 in %EWL model, and β: - 6989 in %EBMIL model) than those who underwent LRYGB. In multivariate mixed analysis, preoperative BMI was not significantly associated with %TWL at 2 years (β, - 0.09 [- 0.22-0.03] p = 0.1). Preoperative BMI was negatively associated with both %EWL (β, - 1.61 [- 1.84-- 1.38] p < 0.0001) and %EBMIL (β, - 1.91 [- 2.16-- 1.66] p < 0.0001).

Conclusions: This is the first study to assess %TWL use for postoperative weight measurement, using a multilevel mixed-effects linear regression model %TWL is the measure of choice to assess weight loss following bariatric surgery.