No weight lifting at all? I find that highly unlikely. Muscle growth like that doesn't occur without resistance training.
Now there are some version of yoga that incorporate a lot of intense body weight exercise or holding weights like medicine balls that could stimulate muscle growth, but that is kind of a modified version of yoga that pulls in weight lifting principles.
you got it ;) resistance pilates and yoga
OK good deal, that makes sense. Yeah I did a sessions of "Yoga+" (something my gym has that is kinda ayoga/pilates hybrid) and I could barely bend at the waist for a week, my core was just destroyed. It was pretty intense for a workout where you don't really move much.