We explain what a calorie is and how this energy value is measured. Also, what they are for and a list of foods with their calories.

calorie - food
Calories became very popular during the second half of the 20th century.

What is a calorie?

When we hear about calories, we must understand by the term a more or less informal unit of energy contained in food, and this is understood by comparing them to the specific heat capacity of water. As the use of calories as a term is not compatible with any formal system of units, it often expresses an ambiguous and indeterminate amount of energy.

calories were defined by Nicolás Clément in 1824, initially as calorie-kilogram (kilocalorie), which is how it was introduced in French and English books between 1842 and 1867. It was stipulated as “the amount of heat necessary to produce a temperature increase of 1°C in a sample of water 1 g” (calorie-gram). However, the use of Joules (J) and its multiples and submultiples, as a unit to measure the amount of energy, is currently considered preferable.

calories became very popular during the second half of the 20th century as part of diets that proposed counting calories as a way of monitoring that the foods consumed were not providing the body with an excess of nutrients that it should store as fat.

See also: Health according to WHO

How are calories measured?

calories - food
Calories are not recognized in the International System (SI) of weights and measures.

Calories (cal) represent the energy value of the food, expressed in the amount of heat needed to increase a mass of water by 1 g by 1 °C. This means that One thousand calories make up one kilocalorie (kcal), equivalent to about 4,185 kilojoules (kJ). With regard to food, these values ​​are usually expressed in terms of kilocalories per 100 grams of food (kcal/100gr). Despite being found on numerous food packages, calories are not recognized in the International System (SI) of weights and measures.

It can help you: Weight measurements

What are calories for?

Calories - food - exercise
It is said that around 7,000 calories are equivalent to one pound of body fat.

Since calories are not a thing, but a unit of measurement, we can say that used to determine the amount of energy contained in thingswhich is particularly useful, as we have already said, to establish some kind of comparison between different foods and their respective impacts on our body’s metabolism.

A higher calorie food will incorporate a greater amount of chemical energy, which, when exceeding what our body needs for its average daily functioning (at least 2,500 calories per day and at rest), is converted into reserves, that is, into fats. It is said that around 7,000 calories are equivalent to one pound of body fat.

How many calories does the food have?

Depends on the food:

  • 100 grams of green vegetables (chard, spinach, watercress) provide 29 kcal
  • 100 grams of lettuce, endive or endive provide 20 kcal each
  • 100 grams of onion provide 47 kcal
  • 100 grams of potatoes provide 79 kcal
  • 100 grams of carrots provide 33 kcal
  • 100 grams of mango, apple and pineapple provide about 50 kcal each
  • 100 grams of figs provide 80 kcal
  • 100 grams of walnuts provide 660 kcal
  • 100 grams of peanuts provide 560 kcal
  • 100 grams of pistachios provide 581 kcal
  • 100 grams of white rice provide 354 kcal
  • 100 grams of pasta provide 368 kcal
  • 100 grams of oats provide 367 kcal
  • 100 grams of lentils provide 336 kcal
  • 100 grams of soy provides 446 kcal
  • 100 grams of anchovies provide 175 kcal
  • 100 grams of red meat provide between 200 and 250 kcal
  • 100 grams of white meat provide between 100 and 180 kcal
  • 100 grams of shellfish provide between 80 and 100 kcal
  • 100 grams of sardines provide 151 kcal
  • 100 grams of tuna provide 225 kcal
  • 100 grams of salmon provide 175 kcal
  • 100 grams of whole milk provide 68 kcal
  • 100 grams of fresh cheese provide 174 kcal
  • 100 grams of cured cheese provides 370 kcal
  • 100 grams of butter provide 752 kcal
  • 100 grams of sugar provide 373 kcal
  • 100 grams of honey provide 295 kcal
  • 100 grams of cauliflower, broccoli or kale provide about 22 kcal each


  • “Calorie” on Wikipedia.
  • “Calories” in Cuidate Plus.
  • “Let’s Learn About Calories” on KidsHealth.
  • “What’s a calorie?” in Good Eating.
  • “What’s a calorie?” (video) by Emma Bryce in Ted-Ed.
  • “What are calories?” in Living Science.
  • “Food Calorie Chart: Fruits, Vegetables and More” at foodspring.