The finding that plasma chemerin levels are raised in human obesity (Bozaoglu et al., 2007; Bozaoglu et al., 2009) and in genetically obese ob/ob mice (Ernst et al., 2010), the adipogenic effect of chemerin (Goralski et al., 2007), and a report of decreased percentage body fat in mice that lack the chemerin receptor CMKLR1 (Ernst et al., 2012) have led to suggestions that raised plasma chemerin levels promote obesity. The gene discussed is RARRES2; the disease is obesity due to melanocortin 4 receptor deficiency.