People with bulimia or anorexia are not receiving the correct treatment, reports a study by the Norwich-based Eating Disorders Association.
Some doctors tell parents eating disorders are a phase
Its survey reveals half of GPs fail to make early diagnosis and many sufferers are not treated by a specialist.
Emma Healy from the association says in many cases it is down to a lack of GP training in this specialist field.
"Doctors should be looking for other signs like personal trauma rather than just a problem with food."
The association wants to end the lottery of treatment by increasing awareness and encouraging more study of the background to the condition.
"Young people with eating disorders may have low self-esteem or have undergone a trigger cause like the death of a close relation or bullying at school," said Ms Healy.
"These mixed together and an eating disorder can be one of the results. People with concerns about their children should also be taken more seriously.
"On our helplines we're still hearing about too many people going to the doctor and being told it's just a phase and they'll grow out of it.
"We know that the earlier you treat an eating disorder the quicker it is to a full recovery."