Belgians have been gradually shifting from a low ratio of polyunsaturated/saturated fat in their food to a higher one with lower total fat and cholesterol. This has occurred predominantly in the north, where the most obvious change is a decrease in butter consumption and an increase in margarine consumption. The northerners have a four to five times smaller intake of butter than the southerners and nearly double the intake of margarine. Evidence gathered over the past ten years reveals in the north a decreasing serum-cholesterol and in the south a significantly higher serum-cholesterol, associated with higher coronary morbidity and mortality. Life expectancy of males in the north is 2-4 years higher at birth and 2-2 years higher at the age of 30. It is concluded that the food habits of a population can be changed, with great benefit.