Richard Klein misses two vital points. One is that in the European context at least, fatness has nearly always been admired in women, not in men; and the other is that extreme fatness and extreme thinness have in common the fact that they effectively prevent you from doing an honest day's work.
Klein writes as though his assertions cross gender lines, yet his only male examples are Edward VII and Louis XVI, whose fatness made them figures of fun, not objects of admiration. Otherwise we are talking of male representations of the female body. The kind of women Rubens painted are far too fat to do anything useful - they are mere passive sofas for men to play on. Whether a woman is obese or skeletal, the underlying meaning is the same: she cannot work, and is a passive status symbol to be owned by a man.
In some poor countries, fat women are admired, because only the rich can afford to get fat. In industrialised countries like ours, just about everyone can afford to get fat by eating greasy chips, Mars bars, etc, but only the rich can afford to get thin, by eating special foods, having personal fitness advisors, etc. Hence thinness is admired.
Class and gender may not explain everything, but any analysis which neglects these basic issues is surely a non-starter.
Tom Gill, Yarnells Hill, Oxford