First of all Im not sure about it, also depend on how 'far back' you are going. Besides, I dont know where you live, but obesity isnt that common where I live, and I think also in most parts of Europe (dont know about America honestly). But anyway obesity really isnt the only factor, there are plenty of skinny unattractive women.Women were a lot thinner back then. Obesity was rare.
Bottom line, today the awareness to health and look is much higher than in old days. people in their 20s back than look like today's 30s.