Re: What (%) of energy is used by the body when one unit of food is eaten?

This is a really good and difficult question to answer.

The process of digestion is known to use some energy. Called the specific dynamic effect, there are differences between the macronutrients. Protein increases the metabolic rate by as much as 30%. Fat and carbohydrate increase the rate by only 5 or 6%. Also, metabolic rate differs between individuals.

In general, the metabolic efficiency of the process of converting food energy to available energy for use by the body is around 40% maximum.

Jill Irvin, RD

Ohio State University