Sense of smell may decode weight bias

A team of US researchers has found that looking at an image of an overweight or obese person could influence one's sense of smell.

Weight bias can affect people's health by increasing their cortisol (stress-inducing hormone) levels that could in turn cause them to eat more.

According to lead author Angela Incollingo Rodriguez from the University of California, Los Angeles, while some people are overtly biased, others are subtler about it and may not even be aware that they harbour negative feelings toward overweight or obese people.

The findings, published online in the International Journal of Obesity, suggest that the extent of negative bias toward overweight and obese people may be greater than previously believed.

To reach this conclusion, the researchers showed subjects one of two sets of images.

Both sets contained photographs of different people - half who were visibly overweight or obese, and half who were of normal weight or thin - along with a series of "distractor" objects.

With each image they viewed, participants were asked to smell a container of lotion tinted with a different food colouring.

As each image appeared, the experimenter placed the "scent sample" under the participant's nose.

The researchers found that when overweight or obese people were on the screen, participants gave worse ratings to the scent samples.

Images of average-sized or thin people tended to trigger higher ratings.

The correlation between visual stimuli and sense of smell is well-established.

Previous research has connected the perception of foul odours to feelings of disgust.

The findings show that prejudice against overweight people is likely to be more pervasive than previously thought, the team said.