The energy density of a food is, in fact, the number of calorie content per weight unit. High-fat foods have high energy density meaning that a weight unit of food contains a significant number of calories. Foods that contain lots of water and dietary fibers have a low energy density, as they contain small amounts of calories per weight unit. Not all foods with high energy density are high in fat (sugar, for example, has a high energy density), as not all foods that contain many fibers have low energy density.
Imagine a unit as a cup the size of a quarter of a cup that you fill with raisins. Then imagine a measure of the size of two cups that you fill with grapes. Both units contain a relative equal amount of fiber and about 100 calories, but the amount of food consumed is 8 times higher in the case of grapes. If you want to get full faster choose to eat the grapes instead the raisins. That way you will keep hunger at bay for longer periods of time.
You are probably asking yourselves how this is possible because raisins are actually dehydrated grapes. Through dehydration most of the water is lost. This decreases the volume of water contained in the fruit, but not the number of calories. Raisins have higher energy density than grapes. Strive to include as many low energy density foods in your system.
This will make losing weight a lot simpler and fun. Feeling hungry is the number 1 reason why people abandon their diet plan. To make sure you stick to your weight loss diet plan eat plenty of low calorie meals that fill you up. There are studies that have shown that our body needs to feel the weight of a certain amount of food before it feels full. Give it that food but make sure it contains just a few calories.