But overweight Western females are actually respected, and receive better treatment.

As a slim white male I don't really agree with that.

The first problem that larger ladies might come across is that Chinese people on the street will often call it as they see it, so as a bigger woman you may well get called fat (pang胖）or strong (zhuang壮）to your face. Of course what we westerners and the Chinese consider as overweight is not the same. A western girl with what we might call curves would likely be considered fat in this country. Finally your comments about body shape and the perceived wealth that is associated with a larger figure might be true for older generations within china who had to live through times of hardship when appearance took a backseat to survival but such attitudes don't persist in modern china with younger generations. Young Chinese woman spend just as much time, money and energy on maintaining their ideal body shape (resembling a 12 year old boy) as western women do and are equally just as bitchy towards those who don't meet the ideal.

In general you have to remember that china is by in large a patriarchal society (I'm aware there are examples of matriarchal societies in the western provinces and Tibet). Particularly away from the big modern cities, china's social development is a longway behind that of the west and therefore opportunities for local women can be limited. I'm frequently bemused by the attitude of both Chinese males and females as to the role of women within the home and society at large. To me it seems like something out of a Jane Austen novel.