Objective: Obesity is a global health problem that increases the risk of coronary artery disease (CAD). However in studies, it has been observed that when the disease develops, obese patients have a more favorable prognosis than leaner patients. This is called the "obesity paradox." This study aims to evaluate the effect of obesity assessed with body fat percentage (BFP) and relative fat mass (RFM) besides body mass index (BMI) on infarct size (IS) estimated from peak creatine kinase-MB (CK-MB) levels in patients with non-ST-segment elevation myocardial infarction (NSTEMI).

Methods: Patients with a diagnosis of NSTEMI who underwent coronary angiography between January 2017 and January 2022 were retrospectively evaluated. Patients without available anthropometric data to calculate BMI, BFP, and RFM and serial CK-MB measurements were excluded from the study. BMI was calculated using weight(kg)/(height[m])² formula. Patients were dichotomized as obese (BMI≥30 kg/m²) and non-obese (BMI<30 kg/m²) to compare baseline characteristics. BFP and RFM were calculated from anthropometric data. Linear regression analysis was performed to define predictors of IS.

Results: Final study population consisted of 748 NSTEMI patients (mean age was 59.3±11.2 years, 76.3% were men, 36.1% of the patients were obese). Obese patients were more likely to be female, hypertensive, and diabetic. Smoking was less frequently observed in obese patients. Peak CK-MB levels were similar among groups. Obese patients had higher in-hospital left ventricular ejection fraction, and less severe CAD was observed in coronary angiographies of these patients. Multivariable regression analysis identified diabetes mellitus, systolic blood pressure, white blood cell count, hemoglobin, and BFP (β=-4.8, 95% CI=-8.7; -0.3, p=0.03) as independent predictors of IS.

Conclusion: Higher BFP is associated with smaller IS in NSTEMI patients. These findings support the obesity paradox in this patient group, but further, randomized controlled studies are required.