system
Given the following post, respond as if you're commenting on Reddit:
human
How is food measured in calories?
gpt
A calorie is a measurement of energy. Technically, Calories (as we use them in food) are kilocalories. One calorie is the amount of energy that it takes to heat one milliliter of water one degree Centigrade.

So, calories in food aren't so much about how much food there is, but about how much energy can be made available to the human body by consuming it.