A Calorie is a unit of energy.
In nutrition the Calorie often refers to the “large calorie” also called kilocalorie and symbolised by “kcal”.
We often use a capital C to distinguish from the small calorie.
One Calorie (kcal) equals 4184 joules and represents the amount of heat needed to raise the temperature of one kilogram of water by one degree Celsius.
Our body needs Calories to function.
The quantity of energy needed depends on age, sex, weight, size, and physical activity.
When we consume foods, our body transforms macronutrient in energy.
One gram of fat contains 9 Calories, one gram of carbohydrates and one gram of protein both contains 4 Calories.
Do you want to know your personal recommendations ?
Your Calorie needs are estimated using the Mifflin St Jeor equation. This equation introduced in 1990 by Mifflin is considered as one of the most accurate. The formula is:
With weight in kilograms, height in centimetres and age in years.
Then we multiply this number by your personal activity factor:
These formulas are based on body mass, which does not take into account the difference in metabolic activity between lean body mass and body fat.
By definition, every Calorie contain the same amount of energy.
However, our body metabolise macronutrients differently: eating 100 kcal of broccoli or 100 kcal of pizza will not have the same impact on body weight.
For example, converting macronutrients to Calories require energy and it differ depending on the type of macronutrients: we burn more calories when we eat proteins compare to fats (2).
Also, consuming fibre riche foods reduce Calorie absorption: one Calorie inside a broccoli is not absorbed the same way as a Calorie inside a pizza. Consuming fibre rich food will not only reduce Calorie absorption but also reduce hunger (3).