Obesity paradox in heart failure: A matter of debate

Nowadays obesity is becoming a global epidemic and public health problem in both children and adults. It is associated with numerous comorbidities such as cardiovascular diseases (CVDs), including atherosclerotic disease, chronic heart failure (CHF), arterial hypertension, type 2 diabetes, certain cancers and sleep apnoea/ sleep-disordered breathing. Moreover, obesity is an independent risk factor for CVD development. Obesity defined by body mass index (BMI) is characterized by better prognosis and lower plasma N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) in CHF patients. Obesity produces an increment in total blood volume and cardiac output that is caused in part by the increased metabolic demand induced by excess body weight. For centuries, the development of cachexia has been viewed as a sign of poor prognosis, and the research interest in CHF is still growing. While it is widely accepted that obesity increases the risk of developing heart disease, numerous publications proved that there is a statistically significant survival benefit in obese patients once they have been diagnosed with CVD. Adamopoulos et al. believed that the obesity paradox is only present in non-diabetic patients with CHF and not in patients with manifest type 2 diabetes. Overall, 29% of the 7788 participants in their analysis were diabetic, which is consistent with several other databases from large-scale CHF trials. In fact, the prevalence of diabetes is usually between 20% and 30% in such cohorts. According to Lavie et al., there are several possible explanations for the obesity paradox in heart failure: non-purposeful weight loss, greater metabolic reserves, less cachexia, protective cytokines or adipokines, earlier presentation due to symptomatology, attenuated response to the renin–angiotensin–aldosterone system, higher blood pressure leading to more optimized cardioprotective medications, different aetiology of heart failure, increased muscle mass and muscular strength in those with high BMI, implications related to cardiorespiratory fitness. In addition, von Haeling et al. believed that the analysis of body composition and its changes over time, as well as patterns of exercise capacity at baseline, were relied on in the published data from large-scale trials. Drawing conclusions from this data, it seems that weight reduction is not good advice for the heart failure patient. Moreover, there are a lot of discussions about the essentials of obesity paradox in specific subgroups, such as gender differences. Due to systolic CHF being more common in men, the majority of research has been conducted in predominantly male populations. This selection bias extends into studies of the obesity paradox in CHF despite accepted variations in fat distribution by sex: women may make up as little as 13% of a study population or the sex of participants may not be reported. However, only BMI was significant for the subgroup of women. And I believe that there is a need for further investigation of CHF outcomes in women. In addition, the levels of peak oxygen uptake (VO2) or minute ventilation (VE)/carbon dioxide production (VCO2) has been identified as an important predictor of survival in CHF. Chase et al. studied a cohort of 744 heart failure patients and found that while patients with obese BMI had significantly lower VE/VCO2 slopes than patients in normal and overweight BMI groups, ultimately VE/VCO2 was a strong independent predictor of improved survival irrespective of BMI. Lavie et al. demonstrated that physical capacity level may actually modify the obesity paradox: in 2066 patients with systolic heart failure, BMI was a significant predictor of ageand sex-adjusted survival in the group with low peak VO2 (<14mL/O2 per kg) (p1⁄4 0.03) but not in the physically active patients. These findings indicated that favourable scores in core components of cardiorespiratory exercise testing might mitigate or even negate the impact of the obesity paradox in CHF, and that exercise training to improve