Oh, trust me, Asian people can get very fat if they try. Most of them just can't afford fast food (McDonalds, KFC, Pizza Hut is incredibly expensive compared to meals they can get from roadside food stalls), or prefer to spend their money on new mobile phones.
Regarding his rebounding, I think it's been agreed around here that he actually CREATES rebounds for his teammates by shoving members of the opposing team out of the way and tipping balls. He is being economical with his energy instead of just lunging for missed shots. And, seriously, "little ass" and Yao don't fit in the same sentence. He's kinda wide.