In experiment 1, normal weight male subjects were provided with three types of breakfast consumed in the Human Appetite Research Unit on separate experimental days 1 week apart. The intensity of hunger, fullness and other subjective feelings were tracked by means of visual analogue rating scales at intervals during the day. Energy and nutrient intakes were measured directly fromad libitumtest meals consumed at lunch and dinner. During the rest of the day and until after breakfast the following day, food intake was measured indirectly through weighed food records. The test breakfasts comprised a basic meal 184 1 kJ (440 kcal) and the same meal supplemented with similar amounts of either fat (1515 kJ, 362 kcal) or carbohydrate (1527 kJ, 365 kcal). No differences were detected between the effects of the basic breakfast compared with the fat‐supplemented breakfast. The carbohydrate supplement suppressed hunger ratings during a limited period after consumption (the post‐ingestive window) coinciding with the expected metabolism of carbohydrate. In experiment 2, a direct test of consumption during this post‐ingestive window confirmed that the carbohydrate supplemented breakfast suppressed intake but the fat supplement did not. These results demonstrate that carbohydrate and fat can produce quite different effects on satiety. Under these experimental conditions the supplement of fat produced no detectable effect on the expression of appetite and illustrates how dietary fat could lead to passive over‐consumption of energy. However this effect may be modified by the particular pattern of food consumption during the course o