Background and Statement of the Problem
In an obesogenic environment characterized by large portions of palatable, inexpensive foods, finding ways to encourage people to eat appropriate amounts and avoid weight gain is challenging. Foods high in energy density (kilocalories per gram), but low in nutrient density, are now pervasive and dominate the choices available in many settings, including convenience stores, vending machines and restaurants. Shifting people to healthier choices is difficult, not only because energy-dense foods are often preferred, but also because foods lower in energy density tend to be less available, less convenient and more expensive.
Dietary energy density has emerged in recent years as one of the most consistent influences on satiety and energy intake. A number of studies have shown that when the macronutrient content of foods was varied, but the energy density was kept constant, the effects of fat, carbohydrate, and protein on satiety were similar. On the other hand, the energy density of foods is a robust and significant determinant of satiety and energy intake regardless of macronutrient composition (1).
The combination of water with the macronutrients in foods determines the energy density, with fat being the most influential macronutrient at 9 kcal/g compared to carbohydrates and protein at 4 kcal/g. The largest influence on overall dietary energy density is water, which contributes weight and volume to a food without supplying any energy (0 kcal/g). Foods with a low energy density provide less energy (calories) relative to their weight than foods with a high energy density. Therefore, for the same amount of energy, a larger, more satiating portion can be consumed when the energy density is low. For example, a 100-calorie snack of strawberries would provide around 13 times more food by weight than 100 calories of pretzels. A growing body of evidence indicates that lowering the energy density of foods by increasing the water content through the addition of vegetables or fruit or by decreasing the proportion of fat or sugar can reduce energy intake and improve diet quality. An evidence-based review by the 2010 US Dietary Guidelines Advisory Committee concluded "that strong and consistent evidence in adults indicates that dietary patterns relatively low in energy density improve weight loss and weight maintenance" (2).
What is the Evidence?
Both laboratory and clinical trial data suggest that reducing energy density shows promise as an effective approach for weight management. For example, in a yearlong trial, women with obesity who were counseled to reduce dietary energy density by increasing intake of fruits and vegetables along with reducing intake of fat had greater weight loss than those who were advised only to reduce fat intake (3). In the multi-center PREMIER trial that included three different lifestyle interventions, dietary changes that reduced energy density were related to greater weight loss after 6 months (4). Additional clinical trials indicate that diets low in energy density can also help patients maintain their weight loss. In one trial, instruction on reducing dietary energy density led to sustained weight loss 36 months after the start of the intervention (5).
The association between energy density and body weight is supported by both longitudinal and epidemiological studies that have tracked dietary patterns (1,2). In a six-year longitudinal study, it was observed that young women who reported a diet higher in energy density gained two and a half times as much weight as those reporting a diet lower in energy density. Longitudinal studies in children have also found an association between dietary energy density and changes in body fat percentage (2). Population-based studies in adults provide additional support for associations between energy density and energy intake, the amount of food consumed, diet quality, and weight status. Surveys of self-reported intakes by free-living adults have shown that normal-weight individuals consume diets with a lower energy density than individuals with obesity. Furthermore, increases in dietary energy density were associated with greater weight gain in a prospective study of 50,000 middle-aged women over 8 years (1,2).
In summary, a number of studies indicate that choosing low energy density foods can help individuals not only to eat satisfying amounts of food that will help to control hunger and manage weight, but also to eat a diet rich in nutrients. A low energy density diet meets the recommendations of most health organizations in that it is full of vegetables and fruits, whole grains, fish and other sources of lean protein, and is low in unhealthy fats and refined carbohydrates.
Data suggest that reducing dietary energy density (kilocalories per gram) can facilitate weight management. If individuals adopt a lower-energy-density eating pattern, they can eat satisfying amounts of food that meet their energy and nutrient needs without gaining weight. Since a range of eating patterns can be accommodated, a diet reduced in energy density has wide applicability and thus can be a key component of a lifestyle that encourages a healthy well-balanced diet for weight management.
- TOS urges food manufacturers to test and market foods that will help individuals to lower the energy density of their diets and to eat appropriate amounts in order to manage their body weight.
- Employers, health plans and public health organizations should work to better communicate how to use dietary energy density for weight management.
- Individuals actively managing their weight should take dietary energy density into account in their food choices and be more aware of lower energy density choices that will help them eat better and feel full with fewer calories.
- Rolls BJ. Plenary Lecture 1: Dietary strategies for the prevention and treatment of obesity. Proc Nutr Soc 2010; 69: 70-79.
- Perez-Escamilla, R, Obbagy, J E, Altman, J, et al. Dietary energy density and body weight in adults and children: A systematic review. J Acad Nutr Diet. 2012; 112:671-84.
- Ello-Martin, J A, Roe, L S, et al. Dietary energy density in the treatment of obesity: a year-long trial comparing 2 weight-loss diets. Am J Clin Nutr. 2007; 85:1465-1477.
- Ledikwe JH, Rolls BJ, Smiciklas-Wright H, et al. Reductions in dietary energy density are associated with weight loss in overweight and obese participants in the PREMIER trial. Am J Clin Nutr 2007;85:1212-1221.
- Lowe, MR, Butryn, ML, et al. Meal replacements, reduced energy density eating and weight loss maintenance in primary care patients: A randomized controlled trial. Obesity. 2014; 22:94-100.