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

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 that is understood by comparing them with the specific thermal capacity of water . Since the use of calories as a term is not compatible with any formal system of units, it often expresses an ambiguous, undetermined amount of energy.
Calories were defined by Nicolás Clément in 1824 , initially as caloriekilogram (kilocalorie), which was how it was introduced in the French and English books between 1842 and 1867. It was stipulated as “the amount of heat needed to produce an increase in temperature of 1 ° C in a 1 g water sample (caloriegram). However, the use of Joules (J) and multiples and submultiples thereof, as the unit for measuring the amount of energy , is now considered preferable .
Calories became very popular during the second half of the twentieth century as part of the diets that proposed calorie counting as a way to ensure that the food consumed did not provide the body with an excess of nutrients that it should store as fat.

How are calories measured?
Calories (lime) represent the energy value of food, expressed in the amount of heat needed to increase a mass of water of 1 gr. This means that one thousand calories constitute one kilocalorie (kcal) , equivalent to about 4,185 kilojoules (kJ). As far as food is concerned, these values are usually expressed in the amount of kilocalories per 100 grams of food (kcal / 100gr). Despite being in numerous food packages, calories are not recognized within the International System (SI) of weights and measures.

What are the calories for?
Since calories are not a thing, but a unit of measurement, we can say that they are used to determine the amount of energy contained in things , which is particularly useful, as we have already said, to establish some kind of comparisons between different food and their respective impacts on the metabolism of our body.
A more caloric food will incorporate a greater amount of chemical energy , which by exceeding what our body requires for its daily average functioning (at least 2,500 calories a day and at rest), it becomes reserves, that is, fat. It is said that about 7,000 calories equals one kilogram of body fat.

How many calories does the food have?
It depends on the food:
 100 grams of green vegetables (chard, spinach, watercress) provide 29 kcal.
 100 grams of lettuce, escarole or endives provide 20 kcal each.
 100 grams of onions provide 47 kcal.
 100 grams of potatoes provide 79 kcal.
 100 grams of carrots provide 33 kcal.
 100 grams of mango, apple, pineapples 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 pistachio provide 581 kcal.
 100 grams of white rice contribute 354 kcal.
 100 grams of pasta provide 368 kcal.
 100 grams of oatmeal provide 367 kcal.
 100 grams of lentils provide 336 kcal.
 100 grams of soybeans provide 446 kcal.
 100 grams of anchovies provide 175 kcal.
 100 grams of red meat contribute between 200 and 250 kcal.
 100 grams of white meat provide between 100 and 180 kcal.
 100 grams of seafood contribute 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 provide 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 cabbage provide about 22 kcal each.