The relationship between dietary energy density and energy intake

Abstract

Much of the research in ingestive behavior has focused on the macronutrient composition of foods; however, these studies are incomplete, or could be misleading, if they do not consider the energy density (ED) of the diet under investigation. Lowering the ED (kcal/g) by increasing the volume of preloads without changing macronutrient content can enhance satiety and reduce subsequent energy intake at a meal. Ad libitum intake or satiation has also been shown to be influenced by ED when the proportions of macronutrients are constant. Since people tend to eat a consistent weight of food, when the ED of the available foods is reduced, energy intake is reduced. The effects of ED have been seen in adults of different weight status, sex, and behavioral characteristics, as well as in 3- to 5-year-old children. The mechanisms underlying the response to variations in ED are not yet well understood and data from controlled studies lasting more than several days are limited. However, both population-based studies and long-term clinical trials indicate that the effects of dietary ED can be persistent. Several clinical trials have shown that reducing the ED of the diet by the addition of water-rich foods such as fruits and vegetables was associated with substantial weight loss even when patients were not told to restrict calories. Since lowering dietary energy density could provide effective strategies for the prevention and treatment of obesity, there is a need for more studies of mechanisms underlying the effect and ways to apply these findings.

Figure 1

Mean (± SE) energy intake at lunch (soup + entrée intake) of 60 women and men in a study testing the effect of varying the form of soup on lunch intake. Subjects consumed significantly less total energy at lunch when soup was eaten as a first course, regardless of its form, compared to when no soup was eaten *(p < 0.0001) Reproduced with permission from Appetite (10).

Figure 2

Mean (± SE) total energy intake at lunch (preload + test meal) for 58 subjects in a study testing the effects on satiety of apple preloads in different forms. Preloads were matched for weight, energy, energy density, and ingestion time; the apple segments, applesauce, and apple juice with fiber preloads were matched for fiber content. Means with different letters are significantly different (p<0.05) based on a mixed linear model with repeated measures. Reproduced with permission from Appetite (16).

Figure 3

Mean (± SE) cumulative energy intake over two days in 26 preschool-age children who were served foods and beverages that were lower in energy density at breakfast, lunch, and afternoon snack. There was a significant effect of energy density on cumulative energy intake starting at breakfast on day 1 and accumulating over the course of the two days when assessed by a mixed linear model (p < 0.01) Reproduced with permission from the American Journal of Clinical Nutrition (37).

Figure 4

Mean (± SE) change in body weight and change in daily weight of food consumed after six months of intervention in 658 participants in the PREMIER trial. Participants were classified into tertiles based on the magnitude of change in dietary energy density. Those with a large reduction in energy density lost significantly more weight than those with a modest reduction or a slight reduction or increase in energy density. Participants with either a large or modest decrease in energy density significantly increased the amount of food they consumed. Values with different superscript letters are significantly different (p < 0.05) using ANOVA with a general linear model adjustment for baseline values followed by a Tukey-Kramer adjustment for multiple comparisons (52).