IL1B and obesity due to melanocortin 4 receptor deficiency: In addition pro-inflammatory cytokines such as IL1β, IL-6 and TNF have been shown to promote HFD-induced obesity and tumorigenesis.31 A20LPC-KO mice fed on HFD for 20 weeks exhibited a marked increase in the severity of lobular inflammation, ballooning, degeneration and overall NAS (sum of steatosis+ballooning+inflammation) when compared with littermate controls on HFD (Table 2).