As an illustration, and with the caveat of not being a formal systematic review and meta-analysis, we have compiled all data we could find on the association of the fat mass and obesity-associated gene (FTO) polymorphism rs9939609 with body mass index (BMI) and obesity in the Brazilian population, by performing a PubMed and LILACS search (for FTO and Brazil; and rs9939609 and Brazil), and searches for FTO and rs9939609 in the Biblioteca Digital Brasileira de Teses e Dissertações (http://bdtd.ibict.br/vufind/). The gene discussed is FTO; the disease is obesity due to melanocortin 4 receptor deficiency.