Forgive the randomness, but was thinking about the calories readout machines in a modern gym give.

Sounds a daft question, but if you eat 100 calories of food, how many calories down the gym do you have to burn on a running machine to lose that 100 calories.

Presumably, a turd has some calorific value, and the body isnt 100% efficient at using the energy it takes in, so im guessing its LESS than 100 calories?