Asian girls are usually quite slim. In countries like Japan, Taiwan, China etc, dieting is like a norm of life and the people usually prefer really skinny bodies, even if it means being severely underweight.
Then again, Asians tend to be shorter. However, Asian models are usually quite tall. The people from the Northern part of China (hope I get this right) are tall, fair and slim naturally, so most models tend to be from that part. Towards the south, they tend to have more yellowish skin tone and shorter too.