The method used is to recruit subjects with extensive mammographic densities and enrol them in a randomized trial in which they receive one of two kinds of dietary counselling. A control group receives general advice about nutrition but is not counselled to change their intake of dietary fat or carbohydrate, and an intervention group is given intensive counselling to reduce their intake of total fat to a target of 15% of calories and increase intake of carbohydrate to maintain intake of total calories.