Objective. Pediatric obesity, a major risk factor for cardiovascular diseases and diabetes, has steadily increased in the last decades. Although excessive inflammation and oxidation are possible biochemical links between obesity and cardiovascular events in adults, little information is available in children. Furthermore, effects of gender and fitness on the interaction between dyslipidemia and oxidative/inflammatory stress in children are mostly unknown. Methods. Therefore, we measured systemic markers of oxidation (F2-isoprostanes [F2-IsoP] and antioxidants) and inflammation (interleukin-6 [IL-6] and leukocyte counts) and metabolic variables in 113 peripubertal children (55 obese [Ob] age and gender-adjusted BMI%≥95th, 25 Females [F]; 15 overweight [OW] BMI% 85th–95th, 8 F; 43 normoweight [NW] 25 F). Results. When compared with NW, Ob displayed elevated F2-IsoP (99±7 vs. 75±4 pg/mL, p<0.005), IL-6 (2.2±0.2 vs. 1.5±0.3 pg/mL, p<0.005), elevated total leukocytes and neutrophils, altered levels of total cholesterol, low- and high-density-lipoprotein cholesterol, triglycerides, free fatty acids, glucose, and insulin (all p<0.005). This pattern was present in both genders and over a broad range of fitness in Ob. Conclusions. Our data indicate that alterations in metabolic control and a concomitant increase in inflammation and oxidative stress occur early in life in obese children, likely exposing both genders to a similar degree of increased risk of future cardiovascular diseases.