Intake of fat and carbohydrate: role of energy density

In this review, we consider two hypotheses which could explain why high-fat foods are overeaten. The first hypothesis is that fat is overeaten because it affects satiety and satiation less than carbohydrate. In several studies which have evaluated the effects of fat on satiety and satiation, fat differed little from carbohydrate when both the palatability and energy density of the test foods were matched. Therefore it is unlikely that the effects of fat on satiety or satiation provide the primary explanation for why it is overeaten. The second hypothesis is that the high energy density of fat facilitates its overconsumption. Support for this view comes from recent studies in which energy density significantly influenced intake when both the macronutrient content and palatability of the test foods were matched. For example, when individuals were fed diets varying in energy density and could eat as much food as they liked, they ate the same amount of food (by weight) so energy intake varied directly with energy density. Furthermore, when participants consumed foods of low energy density, they felt satisfied, despite reductions in energy intake. These findings show that energy density is a key determinant of energy intake in that cognitive, behavioral, and sensory cues related to the volume or weight of food consumed can interact with or override physiological cues associated with food intake.