To be honest, ten minutes later she contradicted herself. Her initial statement probably meant "if you don't train, you will start losing muscle at 20", but that's about as informative as saying "if you don't eat food you will eventually die". Instead her statement made it sound like an inevitability. She even showed a picture of a comically-morphed bodybuilder to illustrate muscle gain, and people laughed, because you know, commitment to an ideal is so fucking funny when you're fat and have no ambition. (I almost lost my shit at that point, but my reaction was lost in the tumult.)