It was recently documented that such abnormalities as increased serum myeloperoxidase (MPO) activity, nitric oxide (NO) formation, and nitrosative damage to proteins are associated with the progression of metabolic disturbances of obesity as well as elevated ONOO—blood concentration may be a valuable predictor of development of hypertension and metabolic syndrome in obese individuals [17]. This evidence concerns the gene MPO and obesity due to melanocortin 4 receptor deficiency.