Energy density

Energy density is the number of calories a food contains per unit of weight or volume.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 131.} Broth-based soup, salad greens, vegetables and fresh fruit have low energy density because they’re mostly water and fiber.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 131.} Fat is the most energy-dense macronutrient: 9 kcal per gram, compared with 4 for carbohydrate and protein.^{2International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 470.}

Large portions of low-density foods can help control hunger and lower calorie intake without supplying excess calories.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 131.}

In practice

• For fat loss, the NSCA recommends building a balanced, varied diet around foods low in energy density.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 131.}
• For a client who isn’t gaining weight, Helms and colleagues suggest more calorie-dense foods.^{3Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 49.} For one who isn’t losing, they suggest foods high in fiber and protein but low in calories, providing more fullness for less energy.^{3Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 49.}
• To raise calorie intake, the NSCA recommends larger portions, more frequent eating and higher-calorie foods.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 131.}

Energy density and nutrient density describe different things: potato chips, desserts and candy are high in calories and low in nutrients, while milk, vegetables, protein foods and grains are nutrient dense.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 211.}