Objective: To estimate the impact of a school-based nutritional and healthy lifestyle intervention to increase the proportions of adolescents free of components of the metabolic syndrome. Materials and Methods: We performed a pre-experimental study in a representative sample of adolescents from two schools in a high Andean district of Peru (Cajamarca city); 388 students completed the intervention and the baseline and post-intervention measurement. The intervention had nine thematic modules; each module was developed in an educational session of 45 minutes every two weeks. We used the National Cholesterol Education Program Expert Panel and Adult Treatment Panel III criteria to identify metabolic syndrome. We used paired proportions comparison (McNemar test) to determine the impact of the intervention. Results. At baseline, 20.4% (95% CI: 16.2 to 24.5) students had no metabolic syndrome components, post-intervention this proportion increase to 32,5% (95% CI: 27.7 to 37.3), the difference in proportions was 12.1% (95% CI: 7.5 to 16.8; p<0.001). The prevalence of metabolic syndrome was 4.6% (95% CI: 2.4 to 6.9) at baseline, while post-intervention was 2.3% (95%CI: 0.7 to 3.9). In the analysis of components, the greatest reduction was in the proportion of hypertriglyceridemia (difference proportions: 21.9%, 95%CI: 16.9 to 26.9, p <0.001), also we found a significant reduction in arterial hypertension (difference proportions: 3.1%, 95% CI: 0.6 to 5.6, p=0.025). In the other components, there were no significant differences. Conclusions. The school-based intervention increased in 59.3% the proportion of students free of any component of the metabolic syndrome.