The start of this is not necessarily going back in time to beginning of when the show started. Thats why Ben is born. It was they never got a divorce not that she wasn't a lesbian. All Ross said was if i never got divorced the first time. Ben would still be there. Its just they're still married.. It was that Monica never lost weight not going back in time to when she was fat. So Rachel and Barry getting married has nothing to do with when Monica wasn't fat anymore. The point is she was still fat.
