Objective: To demonstrate the impact of supplementation with n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) on the prevalence of metabolic syndrome (MS) of obese adolescents.

Material and methods: In a randomized clinical design, obese individuals were selected and randomly assigned to receive 1.2 g n-3 LCPUFA daily during 3 months together with a hypocaloric diet (O3), or 1.0 g sunflower oil and a similar diet as placebo (P). Dietary information, using the multiple pass 24h-recall questionnaire, blood pressure and anthropometry were monthly registered. Peripheral blood samples were obtained at inclusion and at the end of follow-up to determine fasting glucose, triglycerides (TAG) and HDL-cholesterol (HDL-C) by colorimetric methods. To diagnose MS we used the IDF cutoff points for central obesity, glucose and HDL-C. However, we used the criteria of the American Academy of Pediatrics to detect hypertension, and for hipertriglyceridemia a cutoff point of 110 mg/dL was considered. Non-parametric statistics, Chi2 test and logistic regression models were used for analysis.

Results: From 354 individuals, 105 and 111 completed the study for the O3 and P groups respectively. Adherence to treatments and changes in anthropometric and biochemical parameters after supplementation were comparable between groups. At baseline, 69 (31%) individuals from the complete sample met the criteria for MS; the frequency was similar in both groups (30.91% vs. 30.97%, p = 0.992) for O3 and P respectively. Likewise, at the end of the study, 63 individuals presented MS and the frequency was comparable between groups (26.36% vs. 32.14%, p = 0.344). Nevertheless, a detailed analysis exhibited that from the 69 individuals with MS at baseline, 30 remitted at the end of the study, but 26 who did not have the syndrome at baseline, acquired it at the end. While the frequency of remission was comparable between groups (12.2% vs. 14.3%, p = 0.734), the frequency of individuals who acquired the syndrome tended to be smaller in the O3 than in the P group (8.18% vs. 15.18%, p=0.10). Adjusting by basal body mass index z-score; Tanner status; and dietary energy, calcium, magnesium and n-3 fatty acids intake, the supplementation with n-3 LCPUFA protected against the risk to present MS at the end of the follow-up (OR = 0.58, IC95 = 0.29, 1.11).

Conclusions: The results of the study provide evidence that LCPUFA n-3 supplementation to obese adolescents protects against the risk to acquire MS.