['Early diagnosis of initial metabolic derangements in young obese children could influence their management; however, this impairment is frequently not overt, but subtle and undetectable by routinely used clinical assays. Our aim was to evaluate the ability of serum proteomic analysis to detect these incipient metabolic alterations in comparison to standard clinical methods and to identify new candidate biomarkers.', 'A cross-sectional study of fasting serum samples from twenty-two prepubertal, Caucasian obese (OB; 9.22\u2009±\u20091.93 years; 3.43\u2009±\u20091.08 BMI-SDS) and twenty-one lean controls (C; 8.50\u2009±\u20091.98 years; -0.48\u2009±\u20090.81 BMI-SDS) and a prospective study of fasting serum samples from twenty prepubertal, Caucasian obese children (11 insulin resistant [IR]) before (4.77\u2009±\u20091.30 BMI-SDS) and after weight reduction (2.57\u2009±\u20091.29 BMI-SDS) by conservative treatment in a reference hospital (Pros-OB) was performed. Proteomic analysis (two-dimension-eletrophoresis\u2009+\u2009mass spectrometry analysis) of serum and comparative evaluation of the sensitivity of routinely used assays in the clinics to detect the observed differences in protein expression level, as well as their relationship with anthropometric features, insulin resistance indexes, lipid profile and adipokine levels were carried out.', 'Study of the intensity data from proteomic analysis showed a decrease of several isoforms of apolipoprotein-A1, apo-J/clusterin, vitamin D binding protein, transthyretin in OB vs. C, with some changes in these proteins being enhanced by IR and partially reversed after weight loss. Expression of low molecular weight isoforms of haptoglobin was increased in OB, enhanced in IR and again decreased after weight loss, being positively correlated with serum interleukin-6 and NAMPT/visfatin levels. After statistical correction for multiple comparisons, significance remained for a single isoform of low MW haptoglobin (OB vs. C and IR vs. non-IR) and Apo A1 (IR vs. non-IR). Assays routinely used in the clinical setting (ELISA/kinetic nephelometry), only partially confirmed the changes observed by proteomic analysis (ApoA1 and haptoglobin).'] Does proteomic analysis allow for early detection of potential markers of metabolic impairment in very young obese children?