MIF is the only factor amongst interleukin 1 receptor antagonist (IL-1Ra), cathepsin S, nerve growth factor (NGF) and IL-18 showing increased release in morbidly obese patients as described by Fain et al. We show that the MIF content of healthy subcutaneous fat tissue correlates with the BMI from the donors underpinning the role of MIF in obesity. Here, IL18 is linked to obesity due to melanocortin 4 receptor deficiency.