Energy density is the amount of energy (as represented by the number of calories) in a certain weight of food. Energy-dense foods have a lot of calories per serving size, while foods with low energy density have fewer calories for the same weight. An example of food with high energy density is ice cream because all those calories from the sugar and fat fit into a small serving size. What's a food with a low energy density? Spinach. There's only a few calories in a whole plateful of raw spinach leaves.
Energy density is determined by the proportion of macronutrients (protein, fat, carbohydrates), fiber and water. Fiber and water have zero calories so the more fiber or water, the lower the energy density. Fat has about nine calories per gram, so typically food that's high in fat is also high in calories (protein and carbohydrates each have four calories per gram).
Low Energy Density
Foods with low energy density include high-fiber green and colorful vegetables. Watery foods like whole fruits tend to be less energy-dense as well. Fruits and vegetables are also nutrient-dense, which means they have a lot of nutrients per serving size.
High Energy Density
Energy-dense foods include sweets, deep-fried foods, French fries, pasta, starchy vegetables, heavy sauces, cheese, nuts and seeds. Not all energy-dense foods are bad for you -- but you need to watch your portion size when you eat them.
Some foods, like soups and beverages, can have high or low energy density. Broth-based soups with vegetables are less energy-dense while creamed soups are more energy-dense. Non-fat milk is less energy-dense than regular milk, and diet soda is less energy-dense than a sugary soft drink.
Energy Density and Weight Management
Weight management is ultimately about watching how many calories you take in verses how many calories you burn. When you fill up on foods with low energy density, you'll feel satisfied while you take in fewer calories.
Of course, the opposite is true too. If you eat mostly energy-dense foods, you'll need a larger volume of food to fill you up, and as a result, you'll take in more calories. That's not good if you want to lose weight, although it may be helpful if you're trying to gain weight. If you are trying to gain weight, be sure to choose energy-dense foods that are still nutritious like avocados, nuts, and seeds rather than high calorie nutrient-poor junk foods.
Tips for Watching Your Weight
Start meals with garden salads or clear soups. This will fill your tummy before you dig into something more energy-dense like pasta, pizza or other high-calorie entree.
Choose fresh berries for dessert. Or if you really want some ice cream or cheesecake , carefully measure out one serving (look for the serving size on the package) to keep your calorie intake in check.
Load your plate with more vegetables. At least half of your plate should be covered with low-calorie fruits and vegetables. Leave a quarter of your plate for your protein source, and the remaining quarter can hold a serving of starchy foods like pasta, potatoes, or rice.
Drink plenty of water. Water has zero calories and may help tide you over until your next meal, or at least until you can find a low energy density snack.
Serve more fruits and vegetables to your kids. Children who eat more fruits and vegetables tend to eat fewer highly energy-dense foods. If you have a child who's a picky eater, keep serving the veggies, sooner or later, they'll find something they like.
Centers for Disease Control and Prevention. "Low-Energy-Dense Foods and Weight Management: Cutting Calories While Controlling Hunger." Accessed June 01, 2012. http://www.cdc.gov/nccdphp/dnpa/nutrition/pdf/r2p_energy_density.pdf.
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