I often see the claim stated as fact but rarely with primary or secondary source material to back it up; I would like to know how accurate this is if anyone with knowledge would like to set me straight.
You can find several related answers in my profile, listed under Standards of Beauty, which are a good support to my answer to Did heavier men and women used to be considered more attractive before industrialization?. It is rather more complicated than heavier people being seen as more beautiful before industrialization and thinner people being seen as more beautiful after it.