FGF21 and Obesity: Cinnamaldehyde (C9H8O), the pungent compound in cinnamon, has been shown to protect rodents against HFD-induced obesity, enhancing body temperature, BAT function, and WAT browning through increased mitochondrial ATP production and UCP1, PGC1α, PPARγ, PRDM16, and fibroblast growth factor 21 (FGF21) expression [55,56].