The recently developed AWL metric, defined as 100% × (initialBMI - BMI) / (initialBMI - 13), is now validated. In contrast to the well-known outcome metrics BMI, EWL, and WL, the AWL metric is independent of the initial BMI. It should replace the misleading EWL metric for comparing weight loss results in bariatric research and for expressing the effectiveness of bariatric procedures. This effectiveness does not act on the total body mass, or on the excess part, but on the alterable part, defined as BMI minus 13 kg/m(2) for all adult patients, female, male, young, and old.

Revision gastric bypass with removal of gastric banding does not affect the "new" weight after the gastric banding but the "old" weight before the banding. Gastric bypass effectiveness was not added to the gastric banding effectiveness; it replaced it. Therefore, the patient-specific steady weight should be preferred for baseline BMI, reflecting an underlying personal craving for calories that remains constant over time and independent of a bariatric procedure. Baseline BMI can be standardized by using the measured weight at first visit before the primary bariatric procedure, also in revision cases.