I read with great interest the article of Fu et al who investigated whether non-alcoholic fatty liver disease (NAFLD) is an early mediator for prediction of metabolic syndrome, and whether liver B-ultrasound could be used for its diagnosis, in a study involving 861 obese children (6-16 years old). In this study, it was reported that NAFLD is not only a liver disease, but also an early mediator that reflects metabolic disorder, and that liver B-ultrasound can be a useful tool for metabolic syndrome (MS) screening. The authors reported that NAFLD and MS were present in 68.18% and 25.67% of obese children, respectively. Moreover, they observed that the prevalence of MS in NAFLD children was 37.64%, which was much higher than that in the non-NAFLD group. Criteria analogous to those of the Adult Treatment Panel III definition for MS were used for children in this study. The reported prevalence data on MS in the young has varied markedly, in large part because of disagreement among the variously proposed definitions of MS. Therefore, in my opinion, a study aiming to assess the association between MS components and NAFLD in obese children has to take into account a simple, easy-to-apply clinical definition proposed by the international diabetes federation for MS. Interpretation of the results of the Fu et al study are limited by another major caveat: that the diagnosis or exclusion of NAFLD was based on liver enzymes and ultrasound imaging, but was not confirmed by liver biopsy. Indeed, it is known that liver enzymes may be within the reference interval in up to 70% of patients with diagnosed NAFLD and that the full histopathological spectrum of NAFLD may be present in patients with normal liver enzymes, which therefore cannot be reliably used to exclude the presence of NAFLD.