"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.
Dirk Smeesters and Naomi Mandel. "Positive and Negative Media Image Effects on the Self." Journal of Consumer Research. March 2006.