by COLIN FERNANDEZ

Last updated at 09:07 30 July 2007

From playground taunts to discrimination at work, prejudice is a fact of life for millions who are overweight.

Now scientists claim to have discovered why.

While it will be of little comfort to anyone who has been bullied over their weight, it is suggested that thinner humans have an inbuilt dislike of fat people because of ancient fears that they may be diseased.

Researchers found that the mere sight of someone who is overweight can trigger feelings of disgust and nausea similar to encountering rotten food.

The research, reported in the journal Evolution and Human Behaviour, claims that our brains have evolved to react to outward signs of disease, such as rashes and wounds, because bacteria and viruses are invisible.

Unfortunately, these signals also include excessive body fat.

"Antipathy towards obese people is a powerful and pervasive prejudice in many contemporary populations," said the team from the University of British Columbia.

"Our results reveal, for the first time, that this prejudice may be rooted in multiple, independent mechanisms."

A questionnaire found that feelings of disgust towards the obese were strongest in people with the greatest fear of disease.

Those who agreed with comments such as "it really bothers me when people sneeze without covering their mouths" were more likely to agree with statements such as "if I were an employer looking to hire, I might avoid hiring a fat person".

Last night, TV presenter-Anne Diamond, who helps people conquer obesity after briefly ballooning to 14st 9lb herself, said: "The research sounds reasonable enough I suppose; obesity is unhealthy and if there is something in us that helps us avoid ill health I can understand that.

"But I don't believe that in the 21st century we can use it as an excuse for prejudice.

"Obesity is an illness, but something becoming so common that it will soon be the norm."