Numerous studies indicate that a high-fat diet (HFD) induces body weight gain and, subsequently, obesity [8,35,36]; for example, Maciejczyk and collaborators (2018) showed that elevated plasma and cerebral cortex levels of malondialdehyde (MDA)—a marker of lipid oxidative damage—alongside increased glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD) activity are established after 8 weeks in animals fed with a HFD [37]. The gene discussed is CAT; the disease is obesity due to melanocortin 4 receptor deficiency.