Epidemiological studies suggest that the Mediterranean diet (MedDiet) may reduce the risk of the metabolic syndrome (MetS). This multicenter, randomized, controlled, parallel trial compared the effect of 2 types of traditional Mediterranean diets, one supplemented with virgin olive oil (VOO) and the other with mixed nuts, with that of a low-fat diet (control diet) on MetS status. One-year MetS prevalence was reduced by 6.7%, 13.7%, and 2.0% in the MedDiet + VOO, MedDiet + nuts, and control diet groups, respectively (P < .05, MedDiet + nuts vs control diet). Incident MetS rates were not significantly different among groups (22.9%, 17.9%, and 23.4%, respectively). After adjustment for sex, age, baseline obesity status, and weight changes, the odds ratios (95% confidence intervals) for reversion of MetS were 1.3 (0.8-2.1) for the MedDiet + VOO and 1.7 (1.1-2.6) for the MedDiet + nuts compared with the control diet. The authors concluded that a traditional MedDiet enriched with nuts could be a useful tool in the management of MetS.