Excessive fat deposition causes obesity that is connected with different diseases. Research into fat deposition is not limited to humans but covers other mammals too. Mice and rats are frequently used model organisms but in the case of farmed animals’ genetic factors affecting milk production and meat quality are researched. As fat deposition is a polygenetic trait, a comprehensive overview of literature is of great significance. There is, however, no periodically updated database enabling the detection of still unknown genetic causes of fat deposition. This master's thesis is composed of the following three parts: the development of a database of mammalian genes for fat deposition, a bioinformatics analysis to define more reliable candidate loci, and the identification of milk fat yield genes in cattle based on GWAS (genome wide association study) approach. The database established in the thesis contains 855 loci for fat deposition in humans, mice, rats and cattle. Furthermore, the previously developed Human Obesity Gene Map was supplemented. In the thesis, genome locations with a higher number of obesity related genes were identified. It was also established that in humans 73 biological pathways are connected with catalogued obesity genes and 103 in mice. One such pathway is the PPAR signaling pathway with respect to which literature was reanalysed and the database supplemented with new candidate genes. Four new cattle genes for milk fat yield (SLC25A43, NAV3, BFAR, TMPRSS11F) were determined, for HS3ST6 the connection was confirmed. SNPs overlapping previously identified QTLs (quatitative trait loci) were detected. Obesity is a complex disease affected by many genes distributed throughout the genome and associated with different biological pathways. The developed database, if periodically updated, will be a useful tool for further research in this field.