Fatty acid binding protein 4 (FABP4), also known as adipose fatty acid binding protein (AFABP), is a low-molecular weight protein that is abundantly expressed in mature adipocytes [14], and has previously been shown to be associated with several metabolic disease states such as obesity, metabolic syndrome, type 2 diabetes, and insulin resistance [17,18]. The gene discussed is FABP4; the disease is obesity due to melanocortin 4 receptor deficiency.