Importantly, Lee et al. found that the serum level of MMP9 did not change significantly 9 months after a bariatric surgery procedure aimed at reducing body weight (whereas MMP2 serum level decreased significantly), yet it inversely correlated with adiponectin, a well-established insulin-sensitizing adipokine, which supports the notion that MMP9 may be associated more with obesity-induced insulin resistance than with obesity itself [46]. This evidence concerns the gene MMP2 and obesity due to melanocortin 4 receptor deficiency.