This trope is OlderThanDirt. While the Baroque paintings of Peter Paul Rubens gave rise to the term "Rubensesque", heavy-set women have been praised as sex symbols since prehistoric times as a sign of maternity. Many an academic has theorized on when and why slim women became the standard of beauty in much of the world, but the social and political aspects of women's body image issues are well beyond the scope of this wiki. What's important to know is that the love for big girls has never fully died down and is still dominant in many cultures.
%%This means don't insert your favorite theory here.