As the story goes (I have never been able to confirm this)....
The most efficient machine known for moving a given amount of weight across a given distance is.... a human riding a bicycle. Nothing else can move as much weight as far at a similar or greater speed for the same amount of fuel used (food in this case).
And in case anyone was wondering the method used for finding out just how much energy is in various foods.... samples of a given food are dried and then burned. If quantity XXX of fuel is used in the retort to completely consume the food product, and quantity YYY is given off by the retort, then YYY - XXX is the energy value of the food being tested. Which is more or less exactly what we do with food- we 'burn' it. Well, some of us burn it and some of us wisely turn it into fat so that we become 'drought and famine resistant' as Homer has said. :-)
Brian