Bastin et al. question the negative results of treating patients with carnitine palmitoyltransferase (CPT) II deficiency and very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency with bezafibrate based on findings in their open-labeled, uncontrolled trial with bezafibrate in patients with CPTII deficiency. Their studies showed grade C evidence for an effect based on in vitro findings in myoblasts and on questionnaires to the patients and the recording of episodes of myoglobinuria in the patients (Bonnefont et al. 2009). None of these assessments evaluated specific clinical or biochemical parameters reflecting the consequences of CPTII deficiency during exercise in adults. Our randomized, double-blind, placebo-controlled study, showing grade B evidence for no effect of bezafibrate in patients with CPTII and VLCAD deficiencies, demonstrated no improvements in muscle fatty acid oxidation or exercise tolerance after bezafibrate treatment (Orngreen et al. 2014).