Are All Calories the Same?

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The old saying that a calorie is a calorie is a calorie, is true outside of our bodies. However, when the calories are consumed and they are inside our bodies that saying doesn't hold up. Calories from fat are very efficient, 95% of calories consumed from fat are stored in the body, however, calories from protein, for example, cannot be stored as consumed protein.

They have to broken down into amino acids and rebuilt in the body where the body needs it. If we need it while we're growing, it will go into our bones and muscles, if we need it because we're athletic, it will go into muscles to repair them. However, if we don't need protein, most of the protein we've consumed is eventually eliminated in the form of urea.

This is a very energy consuming process and makes protein a very inefficient food source when it comes to calories. So calorie is not a calorie is not a calorie in our bodies, it depends on its nature.