All About Calories
Calories! Many of us (me included) have spent our lives counting them, avoiding them, even fearing them. So, I thought I’d try to capture in one place some facts about calories and then share what I have come to think about them.
- The definition of a “gram calorie” is as follows “The amount of energy required to raise the temperature of 1 gram of water from 14.5’c to 15.5’c, at standard atmospheric pressure.”
- The definition for the “kilogram calorie” is the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius. The Kilogram calorie is also known as: the large calorie; a food calorie and/or Calorie with a capital C.
- When calories are used in nutrition, and especially in food labelling, they are, strictly speaking, ‘large calories’, i.e. kilo calories, denoted by kcal as an abbreviation. However, the word kilo is invariably dropped to avoid confusion with kiloJoules and that just returns us to the word calorie.
- The definition of a kiloJoule (kJ), as used in the context of food energy, is the amount of solar radiation received by one square meter of the earth in one second. (Someone had time to spare coming up with that!) One kiloJoule is 1,000 Joules. The kiloJoule is the unit officially recommended by the World Health Organisation and other international organisations. In some countries only the kiloJoule is found on food packaging, but the calorie is still the most common unit in many countries and in almost every diet book.
- One kilocalorie (kcal) is approximately equal to 4.1868 kilojoules (kJ). The example I have readily to hand is a 100g bar of 90% cocoa dark chocolate. The label says this has 580kcal and 2,400kJ, which gives a conversion of 4.1379 – close enough considering likely rounding to both 580kcal and 2,400kJ.
Whenever I use the word calorie, I am, strictly speaking, talking about a ‘large calorie’, but we all know these things as just calories. Calories to me are whatever a banana has approximately 80 of!