u/HiveMindMacD

From a caloric intake stand point how efficient are we at converting our food to energy in comparison to say an internal combustion engine. I understand that a calorie is a heat measurement. But is the written calories on a food item total calories or an estimate of what we would extract out of it?

A fuel engine would consider heat dissipating through the block a wasted energy but for us heat from our food is useful. Are there too many variables at play here?