All proteins and all carbohydrates have 4 calories per gram and all fats have 9 calories per gram, but not all foods have the same number of calories per unit of volume. Let me explain:
Imagine for a moment, two measuring cups (the kind you have in your kitchen) and notice the amount of space in each container. Got it? Now visualize the two cups side by side; one filled with chopped cucumber and one filled with raisins. Each cup now contains exactly the same VOLUME of food, right? But did you know that the cup of raisins has 37 times more calories? That’s right! The cup of cucumbers contains 14 calories, while the cup of raisins contains 520 calories. If cucumbers and raisins both have four calories per gram, then how could this be? The answer has to do with calorie density. The cucumbers have a lower calorie density because they have a higher fiber and water content. The calories in the raisins are more “concentrated.”