[en] To assess the impact of body mass index (BMI) on cardiac adrenergic derangement, measured by iodine-123 meta-iodobenzylguanidine (${}^{123}$I-mIBG) imaging in heart failure (HF) patients. Overweight and obesity represent relevant health issues, and augmented sympathetic tone has been described in patients with increased BMI. An extensive literature supports that HF-dependent cardiac denervation, measured through mIBG parameters, is an independent predictor of cardiovascular outcomes and mortality. However, the influence of BMI on cardiac mIBG uptake has not been largely investigated. We prospectively enrolled patients with systolic HF, collecting demographic, clinical, echocardiographic data, and mIBG imaging parameters. In order to detect the factors associated with mIBG parameters, a model building strategy, based on the Multivariable Fractional Polynomial algorithm, has been employed. We studied 249 patients with systolic HF, mean age of 66.4 ± 10.6 years, and mean left ventricular ejection fraction (LVEF) of 30.7% ± 6.4, undergoing cardiac ${}^{123}$I-mIBG imaging to assess HF severity and prognosis. Seventy-eight patients (31.3%) presented a BMI ≥ 30 kg/m${}^2$ and obese patients showed a significant reduction in early heart to mediastinum (H/M) ratio (1.66 ± 0.19 vs. 1.75 ± 0.26; p = 0.008) and a trend to reduction in washout rate (33.6 ± 18.3 vs. 38.1 ± 20.1; p = 0.092) compared with patients with BMI < 30 kg/m${}^2$. Multiple regression analysis revealed that BMI, age, and LVEF were significantly correlated with early and late H/M ratios. Results of the present study indicate that BMI, together with LVEF and age, is independently correlated with cardiac mIBG uptake in HF patients.