Image caption Birmingham Children's Hospital has one of only a few specialist eating disorders units

Jane had reached crisis point in the days running up to her 16-year-old daughter, Lily, being admitted to hospital with anorexia.

"In the end I couldn't manage it. I'd had to leave work. I couldn't do shifts because I was so worried about her safety," she recalls.

Jane had spent months trying to persuade Lily to eat, ever since she began slimming for her school prom and then cutting out all carbohydrates and fat from her diet.

"I had to try and get food down her, but it was incredibly hard. I was fighting to get local treatment and support while trying to stop her from getting thinner and thinner. I was beside myself."

Lily became a patient in the child and adolescent eating disorder unit at Birmingham Children's Hospital, which caters for 12 to 18-year-olds, towards the end of 2011 and stayed for eight months.

She got so used to hospital food, even now we've got to have sandwiches in triangles. Jane, Lily's mum

It is one of only four such NHS units across the UK set up to meet the demand for a specialist in-patient service for young people.

Regain control

Jane remembers feeling "quite relieved" on the day she dropped Lily off with a bag containing new pyjamas and comfortable clothes. Lily, she says, was "a bit numb".

All Jane knew was that somebody needed to help her to take care of her daughter. Just 45 minutes' drive away, the Birmingham unit appeared to be the answer.

"When they come to us things are pretty bad," says Dan O'Mara, psychiatric nurse and manager of the eating disorders unit.

"We tell them something has to change quickly."

The Maudsley Approach Also known as the family-based treatment, it is based on the principle that parents play an active and positive role in their child's recovery by helping to restore their weight to normal levels. The approach opposes the idea that families should be blamed for the development of anorexia. It also seeks to limit time spent in hospital by helping parents to regain control at home. The treatment was conceived by a team of child and adolescent psychiatrists and psychologists at the Maudsley Hospital in London, hence its name.

The aim is to help patients reach a healthy weight and encourage good eating habits.

Most importantly, parents are expected to play a key part in their child's recovery - as The Maudsley Approach to treating eating disorders recommends - so that families can regain control over their lives.

Parents often say that meal times turn into battlegrounds as child and parent fight over how much food is eaten.

The unit gives young patients a clear timetable to follow and, with the support of experienced staff, there is an expectation that they will eat a variety of different foods.

Although Lily would eat for the staff at the unit, she would not eat for her mother when she visited, which Jane found distressing.

"I cried in the car after every visit for eight months," she says.

Postcode lottery

Around this time, in a family home in Yorkshire, another young girl was losing more and more weight. It started with regular swimming training and lots of exercising in her room before her parents, David and Louise, noticed their daughter was refusing biscuits and turning down meals.

Katie was just nine.

They had spent months trying to get her to eat proper meals and weeks trying to persuade their GP to take their daughter's problem seriously.

"The GP kept telling us 'calm down, she will be fine', but we took her to the local hospital ourselves and she was kept in for three weeks," Louise says.

Katie's weight had dropped to 3st 4lb (21kg) and her BMI was 12.

Eating disorders There are three main eating disorders - anorexia nervosa, bulimia nervosa and binge-eating disorder.

Anorexia is a serious illness which can be life-threatening.

It stems from low self esteem and an inability to cope with worries and problems. This can lead to cutting out particular types of food, skipping meals and over-exercising.

People with anorexia nervosa eat very little, lose a lot of weight and, for girls, their periods become irregular or stop.

People with bulimia nervosa also worry a lot about weight. They alternate between eating next to nothing, and then having binges when they gorge themselves.

Bulimics vomit or take laxatives to control their weight.

Eating disorders are more common in girls, but they do occur in boys. Beat: Beating eating disorders

When she came home, she had put on a small amount of weight but her parents knew the hard work was just beginning. Their local child and adolescent mental health services team said they did not have the resources to provide the support the family needed for Katie at home.

Their only option was to find a place for her at a hospital which had experience of dealing with children with eating disorders - but it was more than 120 miles away at Birmingham Children's Hospital.

"It's a postcode lottery," says David. "We wanted to keep her at home with us and her two brothers, but it wasn't possible."

Katie was too young to be admitted to Birmingham's specialist unit. Instead, she was given a bed in the hospital's general mental health ward.

The four months Katie spent as an in-patient were the most difficult of their lives, her parents admit.

"We drove down to visit her every weekend but when we left every Sunday evening it was horrendous. We would leave her distraught. In the end she was so homesick, they said they needed to let her go home," Louise says.

In or out?

Family therapy works well as a first step, as an out-patient, but it doesn't work for everyone Dr Nadia Micali

Experts say there appear to be more children coming forward with eating disorders but it is impossible to know how many there actually are.

Dr Nadia Micali, senior lecturer and honorary consultant psychiatrist at University College London's Institute of Child Health, says the latest figures show that 40 in 100,000 10 to 14-year-olds are diagnosed with eating disorders, including anorexia and bulimia.

"In my experience 5-15% might require in-patient treatment."

But she acknowledges that the treatment for eating disorders is still imperfect.

"Family therapy works well as a first step, as an out-patient, but it doesn't work for everyone."

Sandwich shapes

Both Lily and Katie have now put on weight following their treatment but they are both still very particular about food and rigid about eating routines.

Katie will not eat any crisps other than those that contain the minimum number of calories - and she knows exactly which ones they are. She also only wants to eat biscuits that look healthy and low-fat food.

Lily, who has returned to her original weight, will not eat unless somebody is with her and she likes the week's meals to be planned in advance. After eight months in hospital, she was only used to socialising with children with eating disorders - and she picked up some interesting preferences.

"She got so used to hospital food, even now we've got to have sandwiches in triangles," Jane explains.

Both sets of parents know it will take time for their children to get better, possibly longer than they realise, but they are determined to believe in full recovery.

Dr Micali says the prognosis is much better for children than adults if the problem is identified early by teachers and GPs and children are treated quickly.

For the parents, this is one battle they will never give up on.