Here is an interesting BBC article about force-feeding little girls with dates and couscous to make them fat. It seems that some Mauritanians still consider being fat to be the symbol of wealth (and therefore also beauty).
Regardless of the fact that it is clearly stupid and cruel practice, the existence of fat people that became fat because of "overdosing" healthy, natural diet gives the possibility to answer the question if being fat is unhealthy per se, or if being fat as a result of eating highly processed food is actually the reason for the many diseases that affect fat people in Western societies.
07/03/07 Update: Also NYT posted an article on that subject. It is even more shocking than the BBC one as here they also say that women take dexamethasone (a steroid) to get fat faster.