OBJECTIVE:Confirmatoryfactor analysis(CFA) was used to test the hypothesis that the components of themetabolicsyndromeare manifestations of asinglecommonfactor.RESEARCH DESIGN AND METHODS:Three different datasets were used to test and validate the model. The Spanish and Mauritian studies included 207 men and 203 women and 1,411 men and 1,650 women, respectively. A third analytical dataset including 847 men was obtained from a previously published CFA of a U.S. population. The one-factormodel included themetabolicsyndromecore components (central obesity, insulin resistance, blood pressure, and lipid measurements). We also tested an expanded one-factormodel that included uric acid and leptin levels. Finally, we used CFA to compare the goodness of fit of one-factormodels with the fit of two previously published four-factormodels.RESULTS:The simplest one-factormodel showed the best goodness-of-fit indexes (comparative fit index 1, root mean-square error of approximation 0.00). Comparisons of one-factorwith four-factormodels in the three datasets favored the one-factormodel structure. The selection of variables to represent the differentmetabolicsyndromecomponents and model specification explained why previous exploratory andconfirmatoryfactor analysis, respectively, failed to identify asinglefactorfor themetabolicsyndrome.CONCLUSIONS:These analyses support the current clinical definition of themetabolicsyndrome, as well as the existence of asinglefactorthat links all of the core components.Comment inAsinglefactorunderliesthemetabolicsyndrome: aconfirmatoryfactor analysis: response to Pladevall et al.[Diabetes Care. 2006]