Exponential decay modeling can define parameters of weight loss trajectory after laparoscopic Roux-en-Y gastric bypass.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass (LRYGB) produces durable and clinically significant weight loss. We aim to characterize the trajectory of weight loss, and demonstrate the predictive ability of three-month performance on final weight loss.

METHODS: Retrospective analysis of 1097 consecutive LRYGB patients allowed for assessment of conformity of various weight loss trajectory models. Establishing exponential decay as the optimal fit, initial, three-month and final BMI values were used to determine empiric rate constants (λ3 ). Empirically derived weight loss curves and associated rate constants (λ) were generated.

RESULTS: Exponential decay optimally characterizes post-LRYGB weight loss trajectory. Final weight loss can be characterized by λ3, as well as by the demographics black race (P = 0.008) and initial BMI (P < 0.001). Stratification by three-month weight loss allowed derivation of weight loss trajectory curves to predict weight at any point until and including plateau.

CONCLUSIONS: Weight loss after LRYGB conforms well to exponential decay, and postoperative trajectory can thus be predicted early. This allows the clinician early identification and intervention upon patients at risk of poor performance.