[positr0n]

I know the efficiencies are variable among people and labels are not exact, but if you eat an amount of chicken breast labeled 100 calories, and an amount of butter labeled 100 calories, don't those numbers represent the amount of protein and fat respectively that the average person would absorb?

[Tarq0n]

Almost. Protein takes a bit more energy to metabolize than fat. It gets even more complicated when food contains indigestible fiber.

[ErikBjare]

I thought the energy needed to metabolize protein was included in the calorie estimation?