Models of average size are just as effective at selling products as ultra-thin models, a social psychologist's research suggests. 

Helga Dittmar of the University of Sussex in England scientifically examined the claim that thinness sells by comparing different types of advertisements, and presented her research at an obesity conference in Ottawa on Wednesday.

The ads featured the Size 0 models common in magazines as well as equally attractive models who had a body size that represents the average Canadian woman, a Size 10 or 12.

The two main findings were:

• Thin models make many women feel bad about their own bodies, while average-sized models do not.
• Average-sized models were just as effective as thin models for promoting body-care products, makeup and products related to thinness, such as diet foods.

"So really, there is no good reason to use ultra-thin models in advertising," Dittmar told CBC Newsworld on Wednesday.

"Women feel more anxious about their body and their body size, and in turn, body dissatisfaction has been shown to be linked to unhealthy eating patterns."

Recently, fashion shows in Madrid, Milan and London have moved to ban the use of models who are underweight. The British government says the "cult of thin" spurs young people towards dangerous dieting.

The moves may reflect the beginning of a backlash against the belief that thin is beautiful.

Dittmar believes seeing more average-sized models in ads would help prevent body dissatifaction and disordered eating.

"It's definitely a step in the right direction, but I still think we've got a long way to go before we will see greater diversity in body shapes in the media."