We observed the activation of PPARα and AMPKα as potential targets in HF/n-3 iBAT, whereby the HF/n-3-induced increase in FGF21 and immune cells might mediate changes in the expression of enzymes related to energy metabolism and/or be involved in the regulation of iBAT activity, respectively [19, 32, 33, 39, 47, 48]. Here, FGF21 is linked to hydrops fetalis.