HAMP and obesity due to melanocortin 4 receptor deficiency: This review is focused on: (1) iron deficiency in obese children and the role of hepcidin in the connection between body fat and poor iron status; (2) iron status and consequence on health, in particular on cognitive function; (3) cognitive function and obesity; (4) suggestion of a possible link between cognitive dysfunction and ID in pediatric obesity; and implications for therapy and future research.