In recent years, research has focused on why fat is so readily overconsumed. Although the palatability of many high fat foods can encourage overconsumption, another possibility is that fat is not very satiating. A number of studies have compared the effects of fat and carbohydrate on both satiation (the amount eaten in a meal) and satiety (the effect on subsequent intake), but have found little difference between these macronutrients when the palatability and energy density were similar. On the other hand, the energy density of foods has been demonstrated to have a robust and significant effect on both satiety and satiation, independently of palatability and macronutrient content. It is likely that the high energy density of many high fat foods facilitates the overconsumption of fat. An understanding of the role that the energy density of foods plays in the regulation of food intake should lead to better dietary management of hunger and satiety in conditions associated with both over- and underconsumption of energy, such as obesity and anorexia.