Introduction: Obesity is a complex condition influenced by genetic and environmental factors. The FTO gene has been associated with obesity through several single nucleotide polymorphisms (SNPs), particularly rs9939609, related to higher body mass index (BMI) and risk of obesity. FTO variants influence the regulation of appetite and energy metabolism by affecting RNA methylation and the expression of key genes in adipogenesis.Objective: To investigate the association between the FTO rs9939609 SNP and genetic ancestry proportions in Latin American populations.Methods: Genotypes for rs9939609 were obtained using VcfTools and the 1000 Genomes Project database. Samples from Latin America were selected, covering four mixed populations: Colombians (n=94), Mexicans (n=64), Peruvians (n=85) and Puerto Ricans (n=104), totaling 347 individuals. To estimate genetic ancestry proportions, 446 SNPs from a panel of ancestry informative markers (AIMs) were used.Results: Individuals with the AA genotype of SNP rs9939609 have a higher proportion of Native American ancestry and a lower proportion of European ancestry compared to TT and AT genotypes. The variability in the proportions of ancestry according to the genotype of the SNP rs9939609 suggests a possible genetic stratification in the Latin American populations studied.Conclusions: These findings highlight the importance of considering ancestral composition in genetic studies related to obesity. More research is needed to understand how gene-environment interactions contribute to obesity in various populations, which could lead to more effective and targeted intervention strategies