iTunes 11 and playlist updating on iPhone

Hi

I have been using itunes 11 for a while and got used to the new function and layout.

But I wanted to have clear and good playlist - so i decided to remove all my playlist on iPhone and only have those i wanna hear.

I have a playlist called gym which I updating after sometime, but the problem is that my playlist are not updating on iPhone, i allways need to remove the song and add them again to get the playlist updated.

anyone have a solution to how to automatically update the playlist from mac to iPhone ??