ELI5: Calories

A calorie is simply a unit used to measure the amount of energy you get from food and drinks, and the amount of energy your body burns to stay alive and active.

Think of your body like a toy car:

• Food is the fuel: When you eat an apple, a slice of bread, or a cookie, you are putting fuel into your gas tank. The energy in that food is measured in calories.
• Movement burns the fuel: When you run, play, think, breathe, or even sleep, your body uses up that energy. This is called burning calories.

• Low-calorie foods: Foods like lettuce, cucumbers, and berries give you a small burst of energy. You can eat a lot of them without getting too many calories.
• High-calorie foods: Foods like chocolate, cheese, nuts, and French fries pack a huge amount of energy into a very small bite.

• If you take in the same amount of calories as your body burns, your weight stays the same.
• If you eat more calories than you burn, your body stores the leftover energy as fat for later, kind of like saving extra batteries in a drawer.
• If you eat fewer calories than you burn, your body uses up that stored energy to keep going.