Given that: (a) IL-17A has a causal role in multiple models of liver injury; (b) IL-17F shares a receptor with IL-17A; and (c) IL-17RA mice are protected from obesity-induced NASH, we hypothesized that both IL-17A and IL-17F signaling through IL-17RA is critical to NAFLD progression. Here, IL17A is linked to obesity due to melanocortin 4 receptor deficiency.