There is circumstantial evidence to support that this moderate fat, MUFA-rich diet will have a beneficial effect on some of the traditional risk factors for cardiovascular disease and type-2 diabetes. However, there is also growing concern that the increased total fat content will lead to weight gain and increased risk of obesity, and secondary to this, type-2 diabetes and cardiovascular disease. This debate has now been taken up by some of the finest scientific journals. To test this hypothesis the largest and longest dietary intervention trial in Denmark is carried out at the Department of Human Nutrition.