The National Diet Heart Study

The national diet heart study is one of the most rigorous diet trials ever conducted. It involved 100,000 people from five different countries and took years to set up. The patients in franc would go for their meals in the cafeteria and get one of two trays. They looked completely identical, so nobody knew what side of the experiment they were on. One tray was food cooked with vegetable oil and everything low fat; the other had everything cooked in saturated fat.