These studies have shown that TIMP-3 inhibits MMP-2 and MMP-9, both of which are involved in adipocyte differentiation [11], [13], [18]; TIMP-3 is a modifier gene for insulin resistance in mice [19] and TIMP-1 KO mice are protected from obesity [15]. This evidence concerns the gene TIMP3 and obesity due to melanocortin 4 receptor deficiency.