Psychologists quizzed 450 12-year-olds at a comprehensive school in the north of England.

They found that 12% of girls and 16% of boys were teased for being fat.

In most cases the youngsters were not overweight, simply larger than their classmates because they were growing at a faster rate.

However, the insults had a profound impact on the psychology of those who were targeted. They developed problems with their self-esteem and became unhappy about the way they looked.

Psychological baggage

Half the girls reacted by dieting. Boys were more likely to respond by taking vigorous physical exercise.

boys resopnd to taunts by taking exercise

Dr Andrew Hill, who conducted the research with fellow Leeds School of Medicine psychologist Jennifer Murphy, said eating disorders such as anorexia nervosa may be linked to "baggage" carried into adult life after such teasing.

"For a small handful it may be the beginning of an eating disorder. It may be one of those events in a pathway to an eating disorder that emerges later in response to another crisis.

"The individual concerned carries around this baggage that was put there during puberty.

"Appearance is very important at this age. It's the most important area that predicts self-esteem. The experience of being victimised is unpleasant - these kids had low self-esteem in almost every area that we measure.

'Not obese'

"They think their appearance is poor, that they're no good at games, and generally not doing well at school.

"Only a few of the children could be classified as medically obese. The majority were in the normal weight range, but still teased about their weight.

"At that age children are at different stages of physical growth, which is a normal feature of puberty. This group were heavier than the other children, but not fat."

Dr Hill and Ms Murphy presented their findings today at the International Eating Disorders Conference in London.

Dr Hill said there were lessons to be learned for people looking after children approaching adolescence.

"Those who have regular contact with kids, teachers and parents particularly, need to be aware of how they relate to weight and talk about weight with their children," he said.