People can be so turned off by obese individuals that they actually imagine a bad smell, according to a new study.

Study participants who were shown images of heavy and thin individuals while sniffing odorless substances rated the “scent samples” as smelling worse when they were paired with images of heavy people.

“Our findings suggest that people may hold negative views of heavy individuals that are sufficiently entrenched that they can cross over into olfactory (that is, smell) perceptions though people may not be aware that they hold such views,” senior author Andrew Ward told Reuters Health in an email.

“This is the first study to show that negative bias toward heavy individuals is sufficient to affect smell perception,” said Ward, a psychology researcher at Swarthmore College in Pennsylvania.

As reported in the International Journal of Obesity, Ward and his colleagues enrolled college students in two separate studies. In the first, 67 participants were shown twelve separate images – four heavy people, four thin people and four pictures of inanimate objects (the “distractor images”). While the participants viewed each image, a researcher placed the odorless sample under their noses.

Participants rated the “scents” paired with pictures of heavy people as lower than samples paired with thin pictures. But the findings weren’t completely clear due to the arrangement of the images, so the researchers repeated the study with additional distractor images. A total of 175 college students participated.

Once again, the odorless samples paired with images of heavy individuals were rated as smelling worse than those paired with images of thin people. And that effect was most pronounced among study participants who were themselves heavy. The extent of negative bias toward overweight individuals may be greater than previously assumed, the authors say.

“Given how pervasive the bias might be, I think it’s important to make people aware of it, especially to the extent that individuals might not otherwise be able to explicitly recognize the bias in themselves,” Ward said.

Angela Meadows, a psychology researcher at the University of Birmingham in the UK who was not involved in the study, said the extent of negative bias toward heavier individuals is pretty well established.

“They experience stigma and discrimination in just about every aspect of daily life - including healthcare, education, legal proceedings, personal relationships - even going shopping is fraught with potential and actual negative experiences,” Meadows told Reuters Health in an email.

“The world is not a friendly place for fat individuals,” said Meadows.

Meadows said most scientific attempts at improving the situation haven't been very successful.

“Public health messages and the 'War on Obesity' aren't helping because they frame the fat individual as the villain, and media representations of fat people are almost entirely negative," she said.

When this stigma is pointed out, Meadows added, people often respond by saying that if fat people don't like being treated badly, they should lose weight.

“Fat is one of the few stigmatized groups who are expected to change themselves in response to being bullied and harassed,” she pointed out.

Meadows said the current study adds to previous evidence showing how much heavier people dislike their bodies.

“Common wisdom suggests that this could motivate them to change, but almost all the evidence points the other way,” she said. “Self-stigma is associated with more binge eating, less frequent exercise, and so on.”

Meadows said that more and more, research is showing that a positive body image is associated with more healthy behaviors, and better health and well being, even at larger body sizes.