Sophie started starving herself in kindergarten, giving up sweets at first, then taking smaller and smaller portions of food. She exercised compulsively on the monkey bars.
But her parents had no idea she was developing anorexia nervosa because the active girl's height and weight looked normal on the pediatrician's growth chart.
"She was slim, but not skeletal," said her mother Anne, a college professor from Washington State, who did not want to use real names to protect their privacy.
Sophie complained of being dizzy, having "itchy skin" and constipation, all symptoms of malnutrition. She later confessed that she had been throwing out her school snacks and lunches.
And one night when her mother was tucking her into bed, she blurted out, "Mommy, I have a problem … I am hungry all the time and I can't eat," remembers Anne. "A voice in my head is telling me not to eat."
When Sophie was finally diagnosed in first grade, she hadn't gained a pound for 10 months and had dropped from the 60th to the 19th percentile on the weight charts.
More than 10 million Americans have eating disorders, which have a 10 percent mortality rate, the highest of any psychiatric illness, according to the National Institute of Mental Health. Look for these upcoming reports throughout Eating Disorders Awareness Week: ABC News will examine why men have a harder time getting an anorexia diagnosis, and we'll give a revealing report on the rise of thinspo (short for thinspiration), a growing web-based movement that promotes anorexia as a lifestyle choice rather than an illness.
Anorexia nervosa is a chronic brain disorder with no known causes. It is rare among young children -- but the number of hospitalizations is on the rise. According to the Agency for Healthcare Research and Quality, the rate jumped 72 percent between 1999 and 2009, the last year for which there are statistics.
Highly inheritable, it is estimated that 56 to 70 percent of those who are anorexic have a family member with an eating disorder or a co-morbidity like anxiety, according to 1to the Kartini Clinic, a Portland, Ore., facility that exclusively treats children and young adults with eating disorders.
Sophie was adopted, so there was no family medical history to turn to.
"Her memories are that her teacher had told her she had to eat healthy -- and she's the kind of kid who reads between the lines of all the rules and follows them to the letter better than anyone else," said her mother. "She is a perfectionist and has always been an anxious kid."
"No one knows what triggers it," said Dr. Julie O'Toole, founder and medical director of the Kartini Clinic. "The science isn't there yet."
"But it's not caused by the media or by pressure to be thin, though people like to blame that," she said. "Parents don't cause eating disorders and children don't choose to have them."
"You can't cause it even if you wanted to," said O'Toole. "It has nothing to do with fashion magazines. We see farm kids, religiously-raised kids who are homeschooled and have no access to television ... who developed anorexia nervosa."
The disorder affects girls 10 times more often than boys in all age groups, but the true numbers may not be known because boys "conceal their illness better," said O'Toole, who is a pediatrician.
Early onset anorexia, under the age of 12, can look different from the adult illness.
"In the classic adult form, they are afraid of getting fat and believe themselves to be fat and quit eating on that basis," she said. "But there are some children 10 and under who refuse to eat and can't tell you why. And it's not kids who never did eat much or picky eaters -- that's a whole different field."
"Out of normal childhood, they begin eating less and less," she said. Children don't have the "sophistication" to plan a diet or consciously cut back on food.
Weight restoration is the key to treatment. "If you do not do this, you do nothing," said O'Toole. Every organ is affected by starvation, including the brain; children who are anorexic show slow cognition.
Anne was desperate, so she went online and found the "Magic Plate," a term used to describe how parents approach feeding their child -- and the website for the organization F.E.A.S.T. (Families Empowered and Supporting Treatment of Eating Disorders).
She read voraciously and a F.E.A.S.T. member directed the family to Evidence Based Treatment Centers of Seattle, where Sophie eventually got help.
O'Toole and other experts believe that parents are "not part of the problem, but part of the solution," and teach them how to "re-feed" their children.
"You have to bring them back to full health or the symptoms –-- fear of fat and food -- won't go away," said Laura Collins, F.E.A.S.T. founder and author of the book, "Eating With Your Anorexic."
Her daughter, 25, has been well for 10 years after a struggle with anorexia. "She was severely ill, but now she is independent and happy," said Collins.
In family-based therapy, Anne learned techniques to "take responsibility" for Sophie's eating, plating her foods and snacks and demanding that she eat before being allowed to play or do activities she enjoyed.
"We created an environment where eating was required," said Anne. "As their weight goes up, they start to get better."
She has learned how to deal with the behaviors that keep children from eating. Counselors helped address Sophie's anxiety with cognitive behavior therapy; she takes antidepressants for anxiety.
Her family later learned she had rituals from mild obsessive-compulsive disorder. "She folded the blanket on her bed just so … or she thought I would die," said Anne.