A KO of the IL1 receptor type 1 gene (Il1r1), which codes for a receptor of IL-1α, IL-1β, and IL-1RN, causes maturity onset obesity on a normal diet but reduces local adipose-tissue inflammation on an HFD despite almost unchanged immune-cell recruitment [72,73]. The gene discussed is IL1R1; the disease is obesity due to melanocortin 4 receptor deficiency.