system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the caloric content of food measured by combusting the food in a bomb calorimeter if our bodies do not combust the food in our stomachs?

It is my understanding that the energy we collect from food comes from the difference between the energy released in the formation of bonds and the energy consumed by the destruction of bonds in the food, but the chemical processes of digestion are fundamentally different from those of combustion, in which O2 is introduced and CO2 and H2O produced. Why do we measure with combustion?

For example, if you were to combust gasoline in a bomb calorimeter, it would produce quite a lot of heat and would therefore have a lot of calories (according to your calorie measuring calorimeter). However, I don't think these are the kind of calories that we can consume if we drink gasoline, so the measurement would be false would it not?

TL;DR Does digesting food extract the same amount of chemical potential energy from the food as combusting it does?
gpt
Burning gives an upper limit to the amount of energy you can get out of combustion. 

If the end products are water and CO2 then it doesn't matter how you get to it, the total energy produced will be the same if the products are the same. Your body simply does the oxidation slowly through a long chain of chemical reactions in order to process it in a way that is beneficial to your body.  If your body exploded compounds it would actually be pretty inefficient. 

Your body however will differ in how it handles that energy along with how much of the reactant actually is used. 

Your body may also lack the tools needed to process some compounds like gasoline as you stated.