ORIGINAL CONTRIBUTIONS Analysis of Gene Candidate SNP and Ancestral Origin Associated to Obesity and Postoperative Weight Loss in a Cohort of Obese Patients Undergoing RYGB David Velázquez-Fernández 1,2 & Gabriela Mercado-Celis 3,4 & Jeny Flores-Morales 3,4 & Diana Clavellina-Gaytán 1 & Ramón Vidrio 1 & Eduardo Vidrio 1 & Maureen Mosti 1 & Hugo Sánchez-Aguilar 1 & Donaji Rodriguez 1 & Pablo León 2 & Miguel F. Herrera 1,2 # Springer Science+Business Media New York 2016 Abstract Introduction Obesity is the result of a complex interaction between multiple genetic traits and psychological, behavioral, nutritional and environmental factors. Objectives The aims of the study were (a) to comparatively evaluate the presence of 20 candidate gene single nucleotide polymorphisms (SNPs) in morbidly obese patients, (2) their association to comorbid conditions and (3) their impact on weight loss after a Roux-en-Y gastric bypass (RYGB). Patients and Methods Two hundred forty-nine patients were eligible for this study. Clinical, anthropometric, biochemical and demographic variables were analyzed. Body mass index (BMI) and composition were assessed by bioelectrical imped- ance. Twenty SNPs were included for analysis. Results There were 168 Mexican mestizos (67.5 %) and 81 (32.5 %) patients with other ancestral origin. One hundred fifty-nine (64.1 %) were females. Mean ± SD age of the gen- eral cohort was 41.1 ± 11.3 years (17–71). Preoperative mean ± SD BMI was 42.5 ± 6.5 kg/m 2 . There were no signif- icant differences between mestizo and non-mestizo for most SNPs except for IFI, LIPC, and ST8SIA2. FTO (OR = 1.71; CI 95 % = 1.14–2.57; p = 0.008) and APOB (OR = 0.31; CI 95 % = 0.14–0.72; p = 0.004) result is statistically associated to high blood pressure and FTO (OR = 2.0; CI 95 % = 1.3–3.1; Electronic supplementary material The online version of this article (doi:10.1007/s11695-016-2501-9) contains supplementary material, which is available to authorized users. * Miguel F. Herrera miguelfherrera@gmail.com David Velázquez-Fernández velazquezmerlin2004@yahoo.com.mx Gabriela Mercado-Celis gemercadoc@unam.mx Jeny Flores-Morales jfloresm@inmegen.gob.mx Diana Clavellina-Gaytán dclavellina@hotmail.com Ramón Vidrio ramon_atlas@hotmail.com Eduardo Vidrio lalovidrio@comunidad.unam.mx Maureen Mosti mmosti@abchospital.com Donaji Rodriguez donnaroor@hotmail.com Pablo León leonc.pablo@gmail.com 1 The American British Cowdray (ABC) Medical Center, Center for Nutrition, Obesity and Metabolic Alterations (CNOAM), Mexico City, Mexico 2 Departamento de Cirugía, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Av. Vasco de Quiroga No. 15, Tlalpan, Belisario Domínguez Sección XVI, CP 14080 Ciudad de Mexico, Mexico 3 National Institute for Genomic Medicine (INMEGEN), Mexico City, Mexico 4 Laboratorio de Genómica, División de Estudios de Posgrado e Investigación, Facultad de Odontología UNAM, Mexico City, Mexico OBES SURG DOI 10.1007/s11695-016-2501-9