The recently discovered ghrelin acylation enzyme, ghrelin O-acyltransferase (GOAT), encoded by the gene MBOAT4 (membrane bound O-acyl transferase 4) [3,4], is emerging as a promising diagnostic and therapeutic target for regulating appetite and conditions related to the ghrelin axis, such as obesity, insulin resistance and type 2 diabetes mellitus [24]. This evidence concerns the gene MBOAT4 and obesity due to melanocortin 4 receptor deficiency.