Moreover, we found enhanced expression of a hepatic hormone, fibroblast growth factor 21 (FGF21), which is known to function to enhance fatty acid and glucose expenditure.6 On the other hand, the phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, catalytic subunit (G6PC) genes involved in gluconeogenesis were not affected.6 These results suggest the potential benefit of H2 in improving obesity, diabetes, and metabolic syndrome. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.