I'm thinking back here and I notice that the dietiticians were feeding Bean more then Bean was supposedly able/wanted to eat, in EG Ender also ate little but was well established as being psycological in nature, so I assumed it was the same thign with Bean he simply didnt want to eat more then he wanted too.
But if Bean's growth for several years is slowed down making him much smaller then the other kids could that also explain why he eats less? body needs less energy and other materials to break down so he eats less and the dietitians not measuring his exact metabilizism rate simply assumed that based on his hight and the average growth rate of kids his age that he should eat such and such amount?
Are there any other little unspecificed things that we simply did not notice that are clues to him being genetically enhanced before it became obvious even to rocks?