This study could add to the current knowledge of low-grade inflammation in obesity and type 2 diabetes and of the changes in weight and metabolism caused by bariatric surgery, and, furthermore, it will be a basis for further studies regarding the impact of bariatric surgery on the possible postprandial inflammatory response measured by YKL-40 and MCP-1. The gene discussed is CHI3L1; the disease is obesity due to melanocortin 4 receptor deficiency.