['Currently, Roux-en Y gastric bypass (RYGB) is the most efficient therapy for severe obesity. Weight loss after surgery is, however, highly variable and genetically influenced. Genome-wide association studies have identified several single nucleotide polymorphisms (SNP) associated with body mass index (BMI) and waist-hip ratio (WHR). We aimed to identify two genetic risk scores (GRS) composed of weighted BMI and WHR-associated SNPs to estimate their impact on excess BMI loss (EBMIL) after RYGB surgery.', 'Two hundred and thirty-eight obese patients (BMI 45.1\u2009±\u20096.2\xa0kg/m(2), 74\xa0% women), who underwent RYGB, were genotyped for 35 BMI and WHR-associated SNPs and were followed up after 2\xa0years. SNPs with high impact on post-surgical weight loss were filtered out using a random forest model. The filtered SNPs were combined into a GRS and analyzed in a linear regression model.', 'An up to 11\xa0% lower EBMIL with higher risk score was estimated for two GRS models (P\u2009=\u20090.026 resp. P\u2009=\u20090.021) composed of seven BMI-associated SNPs (closest genes: MC4R, TMEM160, PTBP2, NUDT3, TFAP2B, ZNF608, MAP2K5, GNPDA2, and MTCH2) and of three WHR-associated SNPs (closest genes: HOXC13, LYPLAL1, and DNM3-PIGC). Patients within the lowest GRS quartile had higher EBMIL compared to patients within the other three quartiles in both models.'] Does a Genetic Risk Score be Associated with Weight Loss Following Roux-en Y Gastric Bypass Surgery?