Energy Density

Energy density refers to the amount of calories in a given weight of food (calories per gram; kcal/g). A food that is high in energy density provides a large amount of calories in a small portion of food, while a food that is low in energy density has fewer calories for the same weight of food. Eating foods of lower energy density has been associated with reduced short-term energy intake and, in some studies, reduced body weight. Thus, consuming a diet that is lower in energy density may be an important strategy to enhance satiety and help with weight management.

The macronutrient and the water content of a food determine the energy density of a food. Fat is the most energy-dense nutrient, which provides 9 calories per gram, followed by carbohydrate and protein which both provide 4 calories per gram. Alcohol provides 7 calories per gram. Water has the greatest impact on energy density because it adds weight to food but no calories. Thus, foods that are higher in energy density typically have a high fat content (e.g., butter, mayonnaise, nuts, chocolate) and/or a low moisture content (e.g., crackers, chips). Conversely, foods that are lower in energy density typically have a low fat content and/or a higher water content (e.g., fruits, vegetables, soup). There are exceptions, however, in that not all high-fat foods are necessarily higher in energy density and all low-fat foods are lower in energy density. For example, cheese, due to its high moisture content, can have the same energy density as fat-free but dry pretzels.

Lowering the energy density of a mixed meal can be achieved in various ways. One strategy is to add water-rich ingredients to a dish, such as water-rich fruits or vegetables, which add weight but not many calories and therefore reduce the overall energy density of the dish. Another strategy is to cut out some fat from the dish, which can be achieved by substituting lower fat ingredients for their full-fat counterparts (e.g., use low-fat cheese instead of full-fat cheese).

The combination of these two strategies can greatly lower the energy density of a meal while increasing its overall volume. Eating a larger volume of food without ingesting many calories can greatly enhance short-term satiety (i.e., the feeling of fullness). For example, studies by Barbara J. Rolls and colleagues have shown that eating a salad or soup, which are both very [Page 227]low in energy density, as a first course reduces intake during the main course of the meal.

In conclusion, the energy density of a food or mixed dish greatly influences the amount of calories it provides for a given weight of food. Eating foods with a lower energy density has been suggested to enhance fullness and reduce caloric intake.