After Roux-en-Y gastric bypass, there is a downregulation of leptin and resistin gene expression, allowing for the normalization of insulin resistance in obesity. Roux-en-Y gastric bypass specifically, a significant downregulation of leptin and resistin gene proportional to greater excess body weight loss while there was no change in the adjustable gastric band. This evidence concerns the gene RETN and obesity due to melanocortin 4 receptor deficiency.