Is he a fussy eater, or does he just get bored having to sit still ? It could also have become a game to him, at eating time he can get mommy to run after him, try not to run after him, shrug and say "maybe later then" as soon as it stops being game, it stops being fun.
Have you tried letting him feed himself ? This often keeps them occupied, or if you are feeding him, give him a toy or two to play with while he eats.
Brandon hates hot food, so if too hot he refuses to eat, while Liam is not fond of cold food, so if he takes too long to eat and it gets cold, he will not eat anymore.
I also found that by changing their cutlery from plastic to stainless steel got them to eat better