A New Zealand professor says his research proves ultra-thin models are a turn-off for female shoppers.
Massey University marketing expert Leo Paas said his research showed models who were "neither too thin nor too large" have the most positive reaction from consumers, with extremely thin models producing a negative response from young women.
Professor Paas conducted two studies on whether thin models made clothing more desirable.
Read more: Skinny models don't sell clothes - research
The first compared a very thin model to one with a body within the ideal body mass index (BMI) range. The second compared seven images of the same model digitally altered in search of "optimum" size body for selling clothes.
In both sets of research, a group of young women were shown the images and asked questions relating to their reaction to the image, their perception of the ethics of the advertiser, and whether they found the garments the model was wearing desirable.
The first study showed young women had a more positive reaction - and found the bikini or skirt the model was wearing more desirable - when the model was in the healthy BMI range.
"If models fall below that ideal BMI range, which is often the case with extremely thin models, they are a turn-off," Professor Paas said.
"What we found was the thin model led to lower scores on all variables involved."
Participants had the strongest negative reaction to an extremely thin model wearing a bikini.
The second round of research found the "optimum" body size was "neither too thin nor too large" and was most likely to encourage women to buy the clothing.
"This confirmed that if companies use very thin models their advertising will be less effective with mainstream consumers," Professor Paas said.
The research comes as new laws in France mean anyone employing skinny, undernourished fashion models, or is found to be "glorifying anorexia", faces fines and prison sentences.
Fashion chain Glassons came under fire in October for using mannequins with visible ribs in their stores. They later removed the mannequins and apologised to customers.
American model Jennie Runk was the face of H&M's summer 2013 swimwear range.
The size 12 model is considered "plus-size", and would be included in Professor Paas' "optimum" model category.
Other models that are a healthy size 12 and model for "plus-size" ranges include Crystal Renn, Ashley Graham and Australian Robyn Lawley.
Professor Paas would not allow the images used in his research to be reproduced because of ethics guidelines.