Some of the first evidence of AHR involvement in lipid metabolism came from a rodent ARH knock-down model which appeared to be protected against diet-induced obesity and diet-related metabolic complications such as liver steatosis (Xu et al., 2015; Zhu et al., 2019; Gourronc et al., 2020). This evidence concerns the gene AHR and obesity due to melanocortin 4 receptor deficiency.