Objective This study aimed to characterize the differences in protein oxidation biomarkers in adipose tissue (AT) as an indicator of AT metabolism and bariatric surgery weight‐loss success. Methods A human model, in which sixty‐five individuals with obesity underwent bariatric surgery, and a diet‐induced obesity animal model, in which animals were treated for 2 months with normocaloric diets, were analyzed to determine the associations between AT protein oxidation and body weight loss. Protein oxidative biomarkers were determined by gas chromatography/mass spectrometry in AT from human volunteers before the surgery, as well as 2 months after a diet treatment in the animal model. Results The levels of carboxyethyl‐lysine (CEL) and 2‐succinocystein (2SC) in both visceral and subcutaneous AT before the surgery directly correlated with greater weight loss in both human and animal models. 2SC levels in subcutaneous AT greater than 4.7 × 106 μmol/mol lysine (95% CI: 3.4 × 106 to 6.0 × 106) may predict greater weight loss after bariatric surgery (receiver operating characteristic curve area = 0.8222; P = 0.0047). Additionally, it was observed that individuals with diabetes presented lower levels of CEL and 2SC in subcutaneous AT (P = 0.0266 and P = 0.0316, respectively) compared with individuals without diabetes. Conclusions CEL and 2SC in AT are useful biomarkers of AT metabolism and predict the individual's ability to reduce body weight after bariatric surgery.

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