If a food is said to have 100kcal do we get all of those?

Question

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

Answer 1

1. No
2. No

First of all, my understanding is that the FDA only requires the calories listed on a nutrition label to be 80% accurate.

Furthermore, the caloric content of food is determined by literally burning it in a bomb calorimeter and measuring how much energy was released by measuring the increase in temperature. Your body is not 100% efficient, and also cannot absorb 100% of the nutrition in the food that we eat. So the calories of a food measured in a lab is only an upper bound on the number of calories you would obtain by eating it.