What is a kcal? How many should you have per day?

During the first industrial revolution two things happened:

1. With the invention of heat engines, physicians had to find a way to define heat.
2. It was a weird time to be alive.

So they invented the CALORIE (from Latin calor = heat) and decided that :

1 cal is the amount of energy required to warm one gram of air-free water from 14.5 to 15.5 °C at standard atmospheric pressure.

Why am I saying this story? For no particular reason, just find it interesting they decided to warm up 1 gram of water from 14,5 to 15,5°C and call it 1 calorie and thought you might find it interesting too.

But apart from heating engines, the calorie has been used since then in nutritional science to describe the energy (in form of heat) that food can release in the body. This is the reason why the phrase “you are burning calories” is so popular. Because that is literally what is happening in our bodies.

Why it is good to find out how many calories per day should you consume?

According to the study linked below from 2013, just by being aware of the amount of kcal the participants were consuming, they could reduce the consumption in an easier way.