The expression of genes encoding cytochrome P450 (CYP-450), cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, which are involved in the oxidation of PUFAs to form oxylipins, was investigated to assess their contribution to the differences in the oxylipin profile observed at study entry between normal weight individuals and those living with obesity. This evidence concerns the gene LOX and obesity due to melanocortin 4 receptor deficiency.