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). So when we use the word calorie, we are actually talking about a kiloCalorie.
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
