If a banana is said to have 100kcal and you and I eat it are we going to get:
1. all of those calories?
2. the same amount of energy or it varies person to person?
In: Biology
The amount of calories is determined by burning the food in a device called a bomb calorimeter that measures how much heat is given off while burning the food. It’s a very simple way of measuring the energy in something.
How much you absorb versus what you pee and poop out, depends on a number of things. Exactly how much energy a person will extract from it (and whether they use it quickly or store it as fat) depends on a lot of things: what you ate, how quickly it passes through your GI tract, hormones, general health, etc. You might get absorb as much as 90% of the energy, but probably a bit less, and it’s going to vary from person to person.
You’ll never get 100% of the calories, but you’ll get most of them if you’re in decent health. On the other hand, if for example you have norovirus and are vomiting and pooping uncontrollably, you just aren’t going to have a chance to absorb anything.
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