The aim of the project is to examine whether the sources of n-3 fatty acids and fish itself differ in their effects on glucose metabolism, lipid metabolism, blood pressure, and serum inflammatory markers. Lipidomic profiles and gene expression will be used for thorough assessment of the possible clinical changes. The study will compare the effects of alpha-linolenic acid containing vegetable oil, fatty fish, lean fish and control diet. The results of this project will help to identify the optimal source of n-3 fatty acids, and reveal the significance of the components of fish other than fatty acids. These data will be useful both nationally and internationally, since highly controlled dietary interventions utilizing new methodology are scarce.

Inclusion Criteria:

• age 40-70 years
• BMI 25-32 kg/m2
• fasting plasma glucose 5.6-7.0 mmol/l
• 2 h plasma glucose in oral glucose tolerance test <=11 mmol/l
• fasting serum total cholesterol <=7 mmol/l
• fasting serum LDL cholesterol <=5 mmol/l
• fasting serum triglycerides <=4 mmol/l

Exclusion Criteria:

• any chronic disease or condition that hamper the ability to follow dietary intervention
• chronic liver, thyroid or kidney disease
• alcohol abuse
• diabetes
• recent weight loss
• recent myocardial infarction
• corticosteroid therapy
• psychiatric disorders which need drug treatment
• cancer under treatment
• fish allergy or other extensive food allergies
• exceptional diets (like Atkin's or vegan diet)