My 8 mth GSD trie to attack me while i feed him. He has developed this strange behaviour recently.?

He is very playful and obeys me all day, but when i feed him, the moment i keep his bowl down he growls and snarls at me, as if i am a stranger about to gobble his food. I ve stopped going near him when he is eating. When he is finished he is again playful and lets me pat him. My question is whether this kind of aggression be allowed at this young age. Going by this way, i am afraid i ll have myself bitten by those huge teeth he shows me when he is eating the food. How should this be tackled or should he be left with this behaviour? Is it because of Puberty that he is aggresive?