eating issues

My son recently has got really obsessed with food he wants to constantly eat if i tell him he cant have something then he really kicks up a fuss and i end up having to stand between him and the kitchen door to stop him helping him self to food. Between meals he gets to snack on carrots yoghurts and and home made ice lollies that i make out of pure fruit juices. We are now at the stage where he wakes up several times a night demanding food. Obvioulsy i dont always give in to his demands as i know that i cant keep feeding him. Has anyone had this issue if so any advice on what i could do?