Therefore, Liu et al. [49] reported that the role of leptin was selective in diet-induced obesity models in Nile tilapia, with leptin activating GLU metabolism, but showing leptin resistance in lipid metabolism regulation in fish fed HFD, while it promoted lipid metabolism and showed leptin resistance in GLU metabolism regulation in fish fed a high-carbohydrate diet (HCD). Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.