ditch the diet coke, that stuff is poison, opt for water instead.
I had a juiced up gym rat tell me the same thing once.
He got so obnoxious about it I had to reply with ;
" You're a walking pharmacy and think my diet coke is unhealthy?"
Undaunted he came back with ; " Yeah, but those cycles are anabolic and build my body. Diet coke is catabolic ."
I nodded, smiled and said ; " aaaaaaahhhhh" as I swigged the diet coke and walked away.