Quick question

[justaksing]

Hey guys,

I've a quick doubt: I've always had a built body, even if i didn't work out, a good chest, good arms (mesomorph body type). Now, my question is: if I go to the gym and start working out to be even better do I lose my natural body shape if I stop one day? A friend of mine told me so, is it true? Does your body become "addicted" to the gym to maintain a good shape?

Thanks a lot.