Kcal means kilocalorie. Calorie (lime) is a unit of energy measurement and has been commonly used to define the energy value of food. Calorie is a measure that does not belong to the International System of Units (SIU) and Joule is the SIU standardized unit for measuring energy. It has been defined that 1 calorie is equal to 4.1868 J (joules).
Calories must be represented by kcal because 1 kcal = 1000 cal. Therefore, it is correct to say that a person needs, for example, 2000 kcal (kilocaries) per day and not 2000 calories (which would be 2000 x 1000).
To ensure survival, humans need to ingest calories. All foods are energy sources because they have calories (the amount varies according to the food).
To prepare a balanced diet, nutritionists use a table with the amount of calories present in each food as a basis. Fatty foods, such as fatty meats and others, contain the most calories.