Impact of Cardiorespiratory Fitness on the Obesity Paradox in Heart Failure with Reduced Ejection Fraction

Abstract Background: Higher body mass index (BMI) has been associated with improved outcomes in heart failure with reduced ejection fraction. This finding has led to the concept of the obesity paradox. Objective: To investigate the impact of exercise tolerance and cardiorespiratory capacity on the obesity paradox. Methods: Outpatients with symptomatic heart failure and left ventricular ejection fraction (LVEF) ≤ 40%, followed up in our center, prospectively underwent baseline comprehensive evaluation including clinical, laboratorial, electrocardiographic, echocardiographic, and cardiopulmonary exercise testing parameters. The study population was divided according to BMI (< 25, 25 – 29.9, and ≥ 30 kg/m2). All patients were followed for 60 months. The combined endpoint was defined as cardiac death, urgent heart transplantation, or need for mechanical circulatory support. P value < 0.05 was considered significant. Results: In the 282 enrolled patients (75% male, 54 ± 12 years, BMI 27 ± 4 kg/m2, LVEF 27% ± 7%), the composite endpoint occurred in 24.4% during follow-up. Patients with higher BMI were older, and they had higher LVEF and serum sodium levels, as well as lower ventilatory efficiency (VE/VCO2) slope. VE/VCO2 and peak oxygen consumption (pVO2) were strong predictors of prognosis (p < 0.001). In univariable Cox regression analysis, higher BMI was associated with better outcomes (HR 0.940, CI 0.886 – 0.998, p 0.042). However, after adjusting for either VE/VCO2 slope or pVO2, the protective role of BMI disappeared. Survival benefit of BMI was not evident when patients were grouped according to cardiorespiratory fitness class (VE/VCO2, cut-off value 35, and pVO2, cut-off value 14 mL/kg/min). Conclusion: These results suggest that cardiorespiratory fitness outweighs the relationship between BMI and survival in patients with heart failure.