Background: The effect of low carbohydrate diet on oxidant-antioxidant status in morbid uncomplicated obese children is very limited. Aim: The present study was designed to evaluate the activities of antioxidant enzymes and oxidant products in obese Saudi children and matched age and genders control subjects before and after low carbohydrate diet. Subjects and Methods: A prospective study has done on 105 Saudi children. They were classified into two groups; uncomplicated morbid obesity, and matched age control. All subjects underwent anthropometric measurements and estimation of the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), the concentrations of reduced glutathione (GSH), malondialdehyde (MDA), advanced oxidation protein products (AOPP) and oxidized low-density lipoproteins (ox LDL) in blood of obese and normal weight children before and after restriction carbohydrate diet. Results: The obese children had a significantly higher body mass index (BMI) and waist-tohip ratio (WHR) compared with controls. The activities of enzymes and GSH levels were significantly reduced in obese children. The mean values of Ox LDL, MDA, and AOPP were significantly elevated in obese children compared to that of normal weight children. Oxidant-antioxidant status improved after 6 months of carbohydrate-restricted diet, which was associated with a reduction of BMI and WHR. Conclusion: Oxidantantioxidant status is changed in morbid obese children and is returned to baseline levels after another 6 months of low carbohydrate diet which should be maintained over time in this age. 

Keywords: Obese children; Body mass index; Malondialdehyde; Superoxide dismutase; Catalase; Glutathione peroxidase; Glutathione reductase; Reduced glutathione, Dietary-restriction of carbohydrates.