['The adaptive immune system has emerged as an unexpected modulator of insulin resistance. B lymphocytes accumulate in adipose tissue and produce pathogenic antibodies that cause insulin resistance.', 'We studied whether circulating immunoglobulins (IgG, IgA and IgM) were related to metabolic risk markers in pre-pubertal children with and without overweight.', 'Subjects were 270 asymptomatic pre-pubertal Caucasian children (145 lean, 125 overweight) recruited in a primary care setting. Assessments included serum IgG, IgA and IgM concentrations (nephelometry), insulin resistance (HOMA-IR) and fasting lipids (triacylglycerol and high-density lipoprotein [HDL]-cholesterol).', 'Overweight children had higher IgG and IgA serum levels than lean children (P\u2009≤\u20090.01). Increasing serum IgG and IgA, but not IgM, were associated with a less favourable metabolic phenotype, consisting of higher HOMA-IR and triacylglycerol and lower HDL-cholesterol, particularly in obese children, in whom serum IgG and IgA were both independently associated with HOMA-IR (β\u2009=\u20090.308, P\u2009=\u20090.017, r2 \u2009=\u20099.5% and β\u2009=\u20090.361, P\u2009=\u20090.005, r2 \u2009=\u200913.0%, respectively) and triacylglycerol (β\u2009=\u20090.343, P\u2009=\u20090.006, r2 \u2009=\u200911.1% and β\u2009=\u20090.354, P\u2009=\u20090.003, r2 \u2009=\u200912.2%, respectively).'] Do increased serum IgG and IgA in overweight children relate to a less favourable metabolic phenotype?