TNF and obesity due to melanocortin 4 receptor deficiency: Key risk factors include drinking patterns, ethnicity, female sex, adolescence, poor nutrition, obesity, hepatitis C infection, and genetic polymorphisms in genes, such as cytochrome P450 2E1 (CYP2E1), glutathione-S-transferases (GSTs), tumor necrosis factor-alpha (TNF-α), and aldehyde dehydrogenase 2 (ALDH2) (3, 4).