"I don't want to grow"

He always asks for some when I drink tea or coffee. Doesn't help that I'm always drinking some (one of my few food weaknesses)! My response is, "You can't have any, it's caffeine. It's not good for you." He used to say, "I want caffeine." Tonight when I said to him, "You want to grow don't you?" He says, "I don't want to grow."