Obesity (Ob) is an accepted major risk factor for the metabolic syndrome (MetS), a combination of at least three of five risk factors, which predispose to high oxidative stress (OS), but all obese do not show symptoms of MetS. There is dearth of data comparing OS homeostasis of severely obese adults with and without MetS, and need for biomarkers to help in differential diagnosis. Erythrocytic lipid and protein damage markers, malondialdehyde (MDA) and protein carbonyl (PCO), antioxidant enzymes erythrocytic superoxide dismutase(SOD), catalase (CAT), plasma glutathione peroxidase (GPX), and total antioxidant capacity (TAC) as ferric-reducing-ability-of-plasma (FRAP) were compared to understand OS homeostasis among 102 severely Ob (body mass index > 30), 102 Ob with severe (z-score > 2) MetS as per National Cholesterol Education Program-Adult Treatment Panel III guidelines and 100 healthy non-obese Controls. MDA/PCO and all antioxidant enzymes were lowest for ObMetS, followed by Ob, indicating greater damage to protein moieties of the erythrocytic membrane. Multiple regression analysis confirmed z-scores > 2 as significant predictor of lowered enzymes and TAC. Receiver Operator Curve analysis predicted that TAC was the most potential biomarker for the diagnosis and prognosis of MetS with an Odds Ratio of 88.5 indicating the high probability that FRAP would be low for ObMetS (z-score > 2) than for Ob with BMI > 30, but z-scores < 1. TAC is qualified as the most effective biomarker to distinguish between severely obese respondents with and without metabolic syndrome, and as a useful candidate for study of homeostatic breakdown in metabolic syndrome and the importance of z-score in assessment of MetS in obese respondents.
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