Proteins form tissue (muscle, tendon, etc.), and serve as fuel.
Fats form fatty tissue (not muscle, etc.), and serve as fuel.
Carbohydrates are transformed into fat, and serve as fuel.
Alcohol does not form tissue, but does serve as fuel.
Tea and coffee (thein, caffein) do not form tissue, and do not serve as fuel.
Extracts (meat extracts, beef tea) do not form tissue, and do not serve as fuel.
The following table is taken, by permission of the U. S. Department of Agriculture, from "American Food Material," by W. O. Atwater, Ph. D., and Chas. D. Woods, B. S.:-.