“One study revealed a disturbing aspect of U.S. women’s and men’s perceptions of the desirability of plump or thin body types (Rozin & Fallon, 1988). Men and women viewed nine female figures that varied from very thin to very plump. The women were asked to indicate their ideal for themselves and their perception of men’s ideal female figure. In both cases, women selected a figure that was slimmer than average. When men were asked to select which female figure they preferred, however, they selected the figure of exactly average body size. So U.S. women think that men want them to be thinner than is in fact the case. A study of 7,434 individuals from 26 cultures in 10 world regions found the same pattern”
Evolutionary Psychology: The New Science of the Mind