Predictors of outcome after gastric bypass surgery

Background: Weight loss outcome predictions after gastric bypass (GBP) surgery based on individual findings have shown relatively little consistency. The present study took a more comprehensive approach, utilizing extensive pre-surgery interview and psychological test data both individually and in composite predictors. Methods: Pre-surgery data were obtained for 131 morbidly obese patients on a 273-item interview and 5 psychological assessment instruments, and weight loss measures (simple weight change and BMI change) were obtained at a mean of 12.8 months following surgery. Results: Individual predictor variables based on existing research findings showed expected but mostly nonsignificant correlations with weight loss. Optimal composite predictor variables were constructed for 4 general areas of pre-surgery assessment as represented in the literature: physical/medical health, psychological health, interpersonal support, and eating disorder. Each composite variable significantly predicted weight loss, and together they showed multiple correlations of .50 with simple weight change and .54 with simple BMI change. Conclusions: Sustained weight loss after GBP was related to a rather wide range of pre-surgery variables, each of which made a small contribution, but composite variables grounded in the general literature provided more effective prediction. It is cautioned that continued success after ≥2 years could be dependent on yet other variables, with a possible contribution from some post-surgery factors.