"Fat is the modern F-word," said Dr Peter Hill, of the University of Leeds, who found in research that young girls are aware that dieting could make them thinner, and that 41 per cent of nine-year-olds wanted to be thinner, though 18 per cent wanted to be larger.
The findings come as the incidence of obesity and the eating disorder bulimia nervosa - dieting followed by bingeing - is rising in industrialised countries, said Dr Glen Waller, of Royal Holloway and Bedford New College, University of London, who appeared with Dr Hill at the association meeting in Birmingham. "We could wipe out almost all the eating problems in the country if we could wipe out obesity," he said. "It is all connected to this worry about being fat. But doctors are reluctant."
Dr Hill said that was because they found the problem difficult to treat, and intellectually unrewarding. "The attitude is, 'who wants to deal with fat people?'"
The efforts of drugs companies to develop pills which would solve those problems were doomed, he said. "There is no magic bullet. It's not going to happen - people gain weight for all sorts of reasons."
Dr Waller added: "It's the clinical ideal to have a pill for dealing with people you don't want to work with - give them a pill and they go away." Such attitudes had led to the huge problems with tranquillisers, with many becoming addicted.
Dr Hill said girls picked up on the attitudes of society towards fat people, rather than picking slim models as their ideal. "Girls want to be like the thinnest girl in the class, not some catwalk star. But it's notable that they don't want to be like the average girl in the class." Boys, however, had different attitudes to size. Their aim was to be bigger and more muscular. "That's not to say that overweight boys don't want to be thinner, though."
Dr Waller said attitudes to those perceived as fat could lead to a spiralling problem. "The more that society says it's bad to be fat, the more it becomes a self-perpetuating cycle."
Dr Hill said obesity was rising, even among children, though there were disputes over definition. In adults there is a standard height-to-weight definition, he said. "But among children the only definition is the heaviest 5 per cent at any particular age."
Even seemingly innocuous objects such as Sindy dolls could be promoters of unhealthy attitudes. Since her introduction 30 years ago, Sindy had lost her brunette bob and doll- like shape, he said. "She is now unashamedly blonde and pointedly thin."