"Real" Women Make Real Women Feel Like Crap
Now, I don't subscribe to the Journal of Consumer Research, and I haven't read the study (in the March 2006 edition), but a posting on Science Blog says looking at "realistic" models like those in the Dove ads (for anti-cellulite cream!) makes women feel bad about themselves. Looking at "moderately thin" women makes them feel better about themselves:

"We demonstrated that exposure to thin models does not necessarily have a negative impact on one's self-esteem," explain Dirk Smeesters (Tilburg University) and Naomi Mandel (Arizona State University). "On the contrary, exposure to moderately thin (but not extremely thin) models has a positive impact on one's self-esteem."

...In the first part of the study, participants selected four representative models in each category – extremely thin, moderately thin, moderately heavy, and extremely heavy – from a larger sample of images. These images were then shown to randomly chosen women in conjunction with a "lexical decision trial" – that is, the participants were timed as they responded to words related to thinness and heaviness.

Looking at moderately thin or extremely heavy models led to an increase in self-perception of thinness and an increase in self-esteem. By contrast, seeing extremely thin or moderately heavy models focused women's thoughts on how heavy they felt.

These results shed light on why magazines featuring only plus-sized models don't have the success of the magazine that feature slim models: "…campaigns featuring moderately heavy 'real women' might not be as inspirational (or effective) as expected," conclude Smeesters and Mandel.

Sploid notes:

Non-skeletal actresses like Scarlett Johansson and Katherine Heigl may have a similarly depressing effect on American women, who can no longer bitch about how all hot actresses starve themselves.

Of course, in America these days, I'm informed (by angry women, typically) that "real" women wear size 14 (which is actually a much greater number due to size inflation by manufacturers...which is why sneering "Marilyn Monroe wore such and such" isn't a good argument). And sure, real women do now wear size 14 (and up)...especially if they eat a lot of crappy "low-fat" food (which leaves you starving-mean 20 minutes later), and never get up off the couch.