Several studies have shown an inverse relationship between obesity and mortality of patients who survived an acute myocardial infarction or a revascularization procedure, the so-called "obesity paradox". These findings should be considered very cautiously due to several confounding factors, not adequately taken into account by the adjustment models. Similar evidences and considerations have been drawn by studies conducted in patients with acute or chronic heart failure. In these clinical conditions, prospective studies to assess the role of intentional weight loss should be specifically designed.