Algorithm for weight loss after gastric bypass surgery considering body mass index, gender, and age from the Bariatric Outcome Longitudinal Database (BOLD)

Both genders have age-independent metrics for which nadir relative weight loss after LRYGB is not influenced by initial BMI. The resulting algorithm nadir BMI = a + (100%−b) × (initial BMI−a) consists of an inert part (a = 10-17 kg/m2) on which the bariatric effectiveness (b) does not act and an alterable part (initial BMI−a) on which it does. The proposed metric percentage alterable weight loss (%AWL) reduces results to constant values for bariatric effectiveness (b), facilitating research on the precise effect of patient characteristics and surgical variables on postoperative weight loss better than %EWL, a metric able to produce false conclusions. Women and younger patients had significantly more weight loss; initial BMI had no effect.