Part of the show Catalysts for Cleaner Environments and Future Energy
Simon via email asked:
Is the caloric content of food when it is stated on the packet the amount of energy given off when it's burned? Does it take into account the amount of energy a human can extract from it by digesting it with things like enzymes? If I were to eat two donuts at once, would I be taking in twice the number of calories and twice the fat as if I'd just eaten one? If I ate ten at once could I really process them as efficiently as if I'd just eaten one?
The calorie content, which is actually kilocalories, is the energy that would be obtained in an experiment were that food to be burned in an excess of oxygen.