Your body gets two-thirds or less of the total calories available in the food. The rest might be used by bacteria in your colon, or might even be passed out whole. Even among cooked foods, digestibility varies.

What percent of calories are actually absorbed?

Under normal circumstances, more than 95% of this food energy is digested and absorbed from the gastrointestinal tract to provide the body's energy needs.

Do you absorb all calories from protein?

Protein contains 4 calories per gram, but a large part of these protein calories is lost as heat when it's metabolized by the body. The thermic effect of food is a measure of how much different foods increase energy expenditure, due to the energy required to digest, absorb and metabolize the nutrients.