> But with many processed and mass produced food products that's simply not the case as it's quite hard to estimate what exact caloric value your body would extract from each portion with so many ingredients from various sources.
Generally speaking, processed foods are more likely to achieve the full thermodynamically available calories, because most of what we consider "processing" makes things more digestible. For example, if you create Cheetos out of corn, you grind corn into meal, then bake it or whatever. When it goes into your stomach, it readily dissolves into an easily-digestible soup of corn specks and oil. If you just eat corn, the kernels have much less surface area available for the digestion process and some parts remain (notoriously) undigested.
That means it's pretty easy to calculate the number of calories that highly processed foods contribute, since it's near the theoretical max.
In theory yes, but in practice it's much more complicated than that.
During the protein crave of the late 90's early 2000's we added protein to everything because doctors said we aren't eating enough of it.
Wheat protein was one of the easiest and the cheapest to work with which is now why we are now having to search for Gluten free dairy products which wasn't an issue 15 years ago.
After proteins fibers became the biggest crave so the food industry found another cheap source for them - boiled saw dust from pine trees.
Processed food isn't simply just ground nutrition it has some really really fucked up stuff in it (fucked up as in weird not indicatively bad).
Generally speaking, processed foods are more likely to achieve the full thermodynamically available calories, because most of what we consider "processing" makes things more digestible. For example, if you create Cheetos out of corn, you grind corn into meal, then bake it or whatever. When it goes into your stomach, it readily dissolves into an easily-digestible soup of corn specks and oil. If you just eat corn, the kernels have much less surface area available for the digestion process and some parts remain (notoriously) undigested.
That means it's pretty easy to calculate the number of calories that highly processed foods contribute, since it's near the theoretical max.