Energy and unit measures calorie and kilojoule

Calorie is a unit measure of energy and heat. Actually, calorie is an outdated measure that is nowadays often replaced by joule. But in the food industry the term calorie is still used, although often in addition to kilojoule. The unit measures calorie and kilojoule are stated on many packaged foods. The stated number is usually based on one hundred grams or one hundred centilitres, but is also increasingly indicated per portion.

Required energy

A body needs energy for three processes.

  1. Staying alive: Most calories are needed to stay alive and to move, keep our heart beating and blood flowing, and breathe. The number of calories required for this is approximately 60 percent of the total number of calories for an average person.
  2. Carrying out activities: Energy is required for all activities that are performed, such as the smallest actions such as moving the fingers to activities that require more energy such as a heavy bike ride. These exercise activities burn approximately 30 percent of calories.
  3. Digestion: The body itself carries out activities by converting food into energy, but this also requires energy and therefore burns calories.

Unit measures calorie and kilojoule

Calorie has the symbol kcal. The symbol for kilojoule is kj. One kilojoule is equal to 1000 joules, which in turn is equal to (rounded) 238 calories. One thousand calories is equal to (rounded) 4200 joules or 4.2 kilojoules.

  • 1 kilojoule = 1000 joules
  • 1000 joules = 238 calories
  • 1000 calories = 4200 joules

Calories seem less

To avoid having to convert, both indications are stated on many packages. For most consumers it is more common to talk about calories than about joules. Perhaps because those numbers are lower than joules. An example: a product has 355 calories equal to 1,410 joules or 1,410 kilojoules. This way the product appears to have fewer calories. Sometimes the terms calorie and joule or kilojoule are used interchangeably without any clear distinction being made, which can lead to confusion.

Number of calories for men and women

Even doing nothing for a whole day still burns approximately 1000 calories. As you move more, for example through sports, the body needs more energy. The consumption of calories is approximately 2,500 per day for normally built men who do not perform heavy work or exercise a lot. For women this is approximately 2000. Deviations from the rule of thumb 2500 and 2000 apply to people who do a lot of heavy work or otherwise exercise more than normal. Smaller people also burn fewer calories.

Convert to body fat

Any calories consumed in excess of 2500 and 2000 are converted into body fat. Once upon a time, storing that fat was necessary to serve as a reserve in times when there was less food. Nowadays, this is no longer the case in prosperous countries. Converting too many calories into fat is approximately the key: 3500 calories yield 500 grams of fat. In the opposite case, 3500 fewer calories will have to be consumed to lose 500 grams of fat. In practice, this is, for example, an extra 500 calories per day to lose 500 grams of fat in a week. For someone who wants to lose ten kilos, these are fabulous numbers and it is logical that this cannot happen in the short term.

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