The assessment of total antioxidant activity seems to have a higher diagnostic value than the evaluation of individual antioxidants separately. Therefore, this is the first study to assess the total antioxidant/oxidant status in morbidly obese patients undergoing bariatric surgery. The study involved 60 patients with Class 3 obesity (BMI > 40 kg/m2) divided into two equal subgroups: morbidly obese patients without and with metabolic syndrome. The analyses were performed in plasma samples collected before surgery as well as 1, 3, 6, and 12 months after a laparoscopic sleeve gastrectomy. Total antioxidant capacity (TAC), ferric-reducing antioxidant power (FRAP), DPPH (2,2′-diphenyl-1-picrylhydrazyl) radical assay, and total oxidant status (TOS) were significantly higher before surgery (as compared to the healthy controls, n = 60) and generally decreased after bariatric treatment. Interestingly, all assessed biomarkers correlated positively with uric acid content. However, the total antioxidant/oxidant potential did not differ between obese patients without metabolic syndrome and those with both obesity and metabolic syndrome. Only DPPH differentiated the two subgroups (p < 0.0001; AUC 0.8) with 73% sensitivity and 77% specificity. Plasma TAC correlated positively with body mass index, waist–hip ratio, serum insulin, and uric acid. Therefore, TAC seems to be the best biomarker to assess the antioxidant status of obese patients.
