Patients with irritable bowel syndrome with diarrhea and obesity are characterized by an increased content of C-reactive protein, fibrinogen, and medium molecules, pro-inflammatory cytokines (TNFα and TGFβ1) with a decreased content of IL-10, as well as an imbalance of prooxidant and antioxidant systems (an increased content of 8-isoprostane and ceruloplasmin). The gene discussed is IL10; the disease is obesity due to melanocortin 4 receptor deficiency.