To date, data are highly contradictory about the direct association of fetuin-A and RBP4 molecule to HDL particle; moreover, data are lacking about the relationship between impaired circulating fetuin-A and RBP4 production and the markers of obesity-related dyslipidemia (i.e., small HDL, mean LDL size, etc.)in a special morbid obese but non-diabetic population. The gene discussed is RBP4; the disease is obesity due to melanocortin 4 receptor deficiency.