What is a Calorie?
A calorie is a unit of energy. Technically a calorie is the amount of heat energy required to raise the temperature of 1 gram of water up 1 degree Celsius (1.8 degrees Fahrenheit).
When applied to food, we are actually talking about a kiloCalorie (1000 calories). However the word Calorie (note capitalization) is used in most literature.
The measure of Calories gives us an indication of the potential energy that food possesses. This can easily be calculated with the following formula:
1 gram of Protein = 4 Calories
1 gram of Carbohydrate = 4 Calories
1 gram of Fat = 9 Calories
1 gram of Alcohol = 7 Calories
Therefore Calories can be calculated simply by knowing the amount of these three building blocks in the food.