The images on those posters don’t seem particularly representative of ordinary people, that’s for sure. If people decide to aspire to those body shapes, that’s a lot of potential failure, because human bodies are delightfully varied, and really shouldn’t be asked to fit such a narrow range of shapes. You might be interested in the anthology of essays The Politics of Women’s Bodies: Sexuality, Appearance, and Behavior (O’Neill Library HQ1206 .P56 2010).