[gommm]

In china and in japan, I don't think it's related to the wealth of white foreigners but more to the fact that peasant who work all day in the field will be more tanned...

Hence, not being tanned was the same as being fat. It showed that one had wealth and didn't need to work hard to get it.

Another possible explanation (at least in japan) is a question of geography. The center of power in japan has usually been around Tokyo or Kyoto and people there tend to be more lightly skinned as people from the south.