The investigators performed this study to evaluate the efficacy of regular ingestion of white fish to reduce cardiovascular risk factors in patients with the metabolic syndrome, compared to a diet with no fish or seafood at all.

This study was designed as a randomized cross-over multicenter clinical trial with participating centers from the CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), coordinated by the Hospital Universitario Ramón y Cajal, Madrid. The investigators included adult patients with the metabolic syndrome as defined by the Third Report of the National Cholesterol Education Program, Adult Treatment Panel III. All the subjects were Caucasian from European ancestry. Patients were randomized after the screening visit to one of two sequences: 1) Sequence 1 to receive fish consumption first and then no fish. The individuals randomized to this arm continued with their previous alimentary habits, avoiding any significant nutritional imbalance, and with an ingestion of 7 serves of hake (each serve consisted of 100g of frozen Namibia hake, Pescanova S.A., Pontevedra, Spain) per week for a period of 8 weeks. Afterwards they continued for another 8 weeks with the same diet except for the avoidance of fish and any other seafood; 2) Sequence 2 for which they started with their previous alimentary habits, avoiding any significant nutritional imbalance, as well as any fish or seafood for the first 8 weeks. Afterwards they were changed to the same diet but with 7 serves of hake per week.

Inclusion Criteria:

• We included adult patients with the metabolic syndrome as defined by the Third Report of the National Cholesterol Education Program, Adult Treatment Panel III.

Exclusion Criteria:

• Fish allergy and positive antibodies to Anisakis spp.
• Morbid obesity with BMI ≥40kg/m2.
• Chronic renal failure.
• Chronic psychopathy.
• Neoplasia.
• Refusal to participate in the study.