When I think of him demanding more food, I picture a fat man sitting at the end of a table slamming his fists on the table shouting "MORE FOOD!", while "he requires more food" makes me think of a sick weak boy on a bed who needs to eat more food to live.
EXIGER: to demand, to urge, to require. (from Barron's 501 Spanish Verbs). I can see how you would want to use "require," but seems like better to go with REQUERIR for that feeling.
This verb has the given meaning, inter alia, of 'calls for'. Notwithstanding this and the fact that 'demands' and 'calls for' differ little in meaning, my answer is marked as incorrect. Has anybody an explanation for this?