http://www.martialdevelopment.com/bl...ractice-taiji/
It is a muscle tone issue, not a fat issue or a strength issue. Yes, Taiji causes it. Some people never encounter it, because their practice lacks a particular quality or quantity (e.g. relaxation), or because the other aspects of their personal exercise routine compensate for it.
Some people assume that every aspect of Taiji must have been designed by a cadre of scientists, in order to maximize combat power and/or beauty. Or at least that the original Taiji was like this, before it was "watered down" (and until their own master rediscovered it). All just another martial arts fantasy.