Both the gene encoding the α subunit of G stimulatory proteins (GNAS1) and the β3 subunit gene (GNB3) of G proteins are associated with obesity and/or hypertension. Moreover, the TT/TC825 polymorphism of GNB3 predicts greater weight loss than the CC825 polymorphism in obese patients (mean body mass index, 35 kg/m²) undergoing a structured nonpharmacologic weight loss program. Gastric banding enforces a low-calorie diet by diminishing the need for volitional adherence. It is unknown whether these polymorphisms predict the variable weight loss in patients after bariatric surgery. Three hundred and four severely obese patients (mean +- SEM age, 42 +- 1 years; 245 women and 59 men; mean +- SEM body mass index, 43.9 +- 0.3 kg/m²) followed prospectively for at least 3 years after surgery were genotyped for theGNB3C825T, G814A,andGNAS1T393 polymorphisms. All analyses were performed blinded to the phenotypic characteristics of the study group. Frequencies of polymorphisms were comparable to those previously published. No polymorphism studied predicted 3-year weight loss or was associated with high blood pressure in severely obese patients after gastric banding. Multivariate analysis of potentially confounding factors such as reoperation rate or use of sibutramine or orlistat revealed similar results (P > 0.1). Regardless of the mechanism(s) involved for these discordant findings, GNB3 C825T, G814A, and GNAS1 T393C polymorphisms do not seem to be reliable predictors of long-term weight loss.