The majority of people with eating disorders are not receiving the recommended level of care, a survey of patients suggests.
Half of all people with anorexia are teenage girls
Last year, the National Institute for Clinical Excellence issued guidelines for treating anorexia and bulimia.
But an Eating Disorders Association survey of 1,700 patients and relatives found 55% of sufferers are not treated by a specialist.
It also found that in 42% of cases, GPs failed to make an early diagnosis.
The EDA said detecting an eating disorder early was "perhaps the most important recommendation" NICE had made.
But it said it received reports every week of GPs failing to detect there was a problem, or of them not acting quickly enough.
The EDA published its analysis of services to mark the beginning of Eating Disorders Awareness Week.
Lack of specialists
It said the lack of access to specialist care was largely due to a shortage of consultant psychiatrists.
In addition, the report found only 14% of the patients, carers or professionals questioned said eating disorder treatment had been available close to home.
The EDA warned that for some people, the nearest appropriate specialist service could be up to 150 miles away.
And only 17% of young people had been treated in settings that were age-appropriate, the survey found.
Access to suitable services is often determined by where a patient lives.
A third of local health authorities have no specialist treatment centres. And there is no specialist adult or inpatient or outpatient services at all in Wales.
Susan Ringwood, chief executive of the EDA, told the BBC News website: "It was shocking that the results were so stark."
She said families rang the association asking how they could help their son or daughter.
"It's hard enough to give them an answer without having to say 'it depends on where you live and it depends on how good your doctor is'."
Training 'is key'
Ms Ringwood added: "What we want to be able to do is be able to look at the situation again in a year's time and be able to report that things have got better."
She said it would take many years to get enough psychiatrists in post to provide the specialist care that patients with eating disorders need.
But she added: "Primary care is the area where we could make a real difference straight away.
"Eating disorders are very difficult to diagnose. They are very secretive conditions, and people don't come into the surgery and say 'I have anorexia'.
"I know GPs only have around 10 minutes with each patient, but diagnosing eating disorders early is important."
Dr Eric Shur, consultant psychiatrist at the Priory Hospital in Roehampton, said: "It is imperative that eating disorders are identified and treated early.
"Sufficient resource needs to be provided both for patients, and for training doctors and nurses if these urgent needs are to be met."
Dr Maureen Baker, honorary secretary of the Royal College of GPs, said: "We understand that 32% of GPs are making an early diagnosis in this area and as the NICE guidance on eating disorders only came out a year ago we feel that this is an improvement.
"However, we would like to see more resources and information made available to help train GPs and other primary healthcare professionals in this area."