Not only ABO blood group system is important for determining hypertension, erythroblastosis fetalis, blood transfusion and exchange reactions12 but has also been shown to be relevant to conditions such as osteodysplasia and as genetic marker of obesity.12 More recent developments are exploring the relationship between ABO blood grouping and obesity13, which was also one of the main objectives of current study. This evidence concerns the gene ABO and obesity due to melanocortin 4 receptor deficiency.