I have not been in this situation and so I don't know how I would feel doing what I suggest. However, if I were in this situation I think that I would give him fruit for breakfast or whenever you normally do and then no more throughout the day (or whenever you do, only do it at those times, so it's consistant)
Then, when he is hungry at the other times of the day offer his regular food make that the only thing you give him no matter what. If you give in he will know he just has to fuss long enough and you will break and he'll get what he wants.
It will probably take a while and he will go hungry for a portion of the day, but if he is hungry enough then he'll eat what he is given.
That is what I would do with my 18m old daughter who is VERY strong willed. I have had similar situations and this method has worked very well.
Hope that was helpful, just be tough and consistant :-)