What is a calorie?
A calorie is a measure of the energy in the food you eat. We all need energy to stay alive, and we get it from food. Your body 'burns' this fuel to make the energy you need.
Why do we need calories?
Different people need different amounts of energy. Your body needs energy to breathe, pump blood, digest food, absorb nutrients and stay active. Some activities use more energy than others. The more active you are, the more energy your body uses up.
Where do calories come from?
Your body gets energy from nutrients: carbohydrates, fats and proteins. Carbohydrates and proteins provide about four calories (sometimes referred to as kilocalories) per gram, while fats provide more than twice as many: nine calories per gram.
Most foods contain a mixture of carbohydrates, protein and fat, so different foods and drinks provide different amounts of energy. Most fruits and vegetables contain few calories. Other foods, like deep-fried chicken wings or French fries, contain a lot of calories.