In the process of animal fat deposition, the proliferation and differentiation of pre-adipocytes and the change of lipid droplet content in adipocytes are regulated by a series of transcription factors and signal pathways. Although researchers have conducted in-depth studies on the transcriptional regulation mechanisms of adipogenesis, there are relatively few reports on post-transcriptional modification on mRNA levels. The modification of mRNA m⁶A regulated by methyltransferase, demethylase and methylation reading protein is a dynamic and reversible process, which is closely related to fat deposition in animals. Fat mass and obesity associated proteins (FTO) act as RNA demethylases that affect the expression of modified genes and play a key role in fat deposition. This article summarized the mechanism of FTO-mediated demethylation of mRNA m⁶A in the process of animal fat deposition, suggesting that FTO may become a target for effective treatment of obesity. Moreover, this review summarized the development of FTO inhibitors in recent years.