Yeah, if she tries to leave you, or tell someone what you told her, just RAGE

and snap her like a twig as you quote the studies that have debunked the roid rage phenomena. And then add, oops, but that was only for test, and I'm on fina.
Alternately, you could say,"Honey, you are right, I will not juice." Then tell her you have got to go to the gym to get huge. End with a threat like, "Got a problem with that, bitch? I didn't think so!" Then smack her with 9 inches of limp dick (or however many you have, it would be rude to borrow a few inches from a passer-by).
Or, deny everything, don't bring it up again. When she comments that you have gained 30 pounds of weight in 5 weeks, and yet you look leaner, avoid the question, but mutter just loud enough for her to hear, "Smashy-smashy...smashy-smashy...Mongo like smashy..."
These are just off the top of my head, but trust me, there are plenty more where those came from.