Abstract
Abstract
Background
In the era of modern metabolic-bariatric surgery, increasing attention is being paid to the assessment of clinical response after surgery. With the growing availability of multimodal obesity treatment, including preoperative pharmacological and lifestyle interventions, identification and optimization of factors associated with a suboptimal clinical response after metabolic-bariatric surgery (MBS) have become increasingly important. When considering weight loss specifically, two methodological factors substantially influence the interpretation of postoperative response: the metric used to quantify weight loss (percent total weight loss [%TWL] versus percent excess weight loss [%EWL]) and the baseline from which the weight-loss trajectory is calculated.
Objective
To illustrate how different weight-loss metrics and baseline definitions influence the interpretation of postoperative response and the apparent association between preoperative characteristics and suboptimal clinical response after MBS.
Methods
We analyzed 17,568 patients from the StuDoQ|MBE registry who underwent primary MBS and had complete 2-year postoperative follow-up data. Postoperative suboptimal clinical response was assessed using the 2024 IFSO reporting threshold of
Results
The proportion of patients classified according to weight-loss-based criteria for suboptimal clinical response varied substantially according to the metric used, with more patients meeting the historical
Conclusion
The choice of weight-loss metric and baseline definition substantially influences the classification of postoperative weight-loss response and the apparent association between preoperative characteristics and surgical outcomes. %EWL and %TWL are not interchangeable measures and can produce opposing interpretations of the association between baseline BMI and postoperative response. Consistent with the 2024 IFSO consensus, weight-loss assessment after MBS should use a baseline established before initiation of preoperative weight reduction where appropriate, particularly when evaluating the overall treatment trajectory. %TWL provides a more readily comparable metric for standardized reporting, whereas %EWL may remain useful for comparison with historical literature. Because clinical response after MBS is multidimensional, weight-loss thresholds should not be interpreted as synonymous with clinical treatment failure.