Anorexia nervosa takes an enormous toll on the body. But that’s not all. It has the highest death rate of any mental illness. Between 5% and 20% of people who develop the disease eventually die from it. The longer you have it, the more likely you will die from it. Even for those who survive, the disorder can damage almost every body system.

What happens exactly? Here’s a look at what anorexia does to the human body.

The first victim of anorexia is often the bones. The disease usually develops in adolescence — right at the time when young people are supposed to be putting down the critical bone mass that will sustain them through adulthood.

“There’s a narrow window of time to accrue bone mass to last a lifetime,” says Diane Mickley, MD, co-president of the National Eating Disorders Association and the founder and director of the Wilkins Center for Eating Disorders in Greenwich, Conn. “You’re supposed to be pouring in bone, and you’re losing it instead.” Such bone loss can set in as soon as six months after anorexic behavior begins, and is one of the most irreversible complications of the disease.

But the most life-threatening damage is usually the havoc wreaked on the heart. As the body loses muscle mass, it loses heart muscle at a preferential rate — so the heart gets smaller and weaker. “It gets worse at increasing your circulation in response to exercise, and your pulse and your blood pressure get lower,” says Mickley. “The cardiac tolls are acute and significant, and set in quickly.” Heart damage, which ultimately killed singer Karen Carpenter, is the most common reason for hospitalization in most people with anorexia.

Although the heart and the bones often take the brunt of the damage, anorexia is a multisystem disease. Virtually no part of the body escapes its effects. About half of all anorexics have low white-blood-cell counts, and about a third are anemic. Both conditions can lower the immune system’s resistance to disease, leaving a person vulnerable to infections.

Even before a person with anorexia starts to look “too thin,” these medical consequences have begun.

Many young women who begin eating a severely restricted diet stop menstruating well before serious weight loss sets in. Since so many people with anorexia are teenage girls and young women, this can have long-term consequences on their ability to bear children.

“In truly, fully recovered anorexics and bulimics, it looks like the rate, frequency and number of pregnancies is normal,” says Mickley. “However, if you look at infertility clinics, and those patients in the clinics who have infrequent or absent periods, the majority of them appear to have occult eating disorders. They may think they’re fully recovered, but they haven’t gotten their weight up high enough.”

Many women with anorexia would rather seek fertility treatment than treatment for their eating disorder, Mickley says. And even among women who have fully recovered from their anorexia and bulimia, there may be a slightly higher rate of miscarriages and caesarean sections. “There also may be up to a 30% higher incidence of postpartum depression as compared to other women,” she says.

Bulimia, which often goes hand in hand with anorexia, does its own unique health damage. Bulimics who purge by vomiting wreak havoc on their digestive tracts by chronically bathing them in stomach acid, which can lead to digestive disorders like reflux esophagitis.

“It feels like I’ve been drinking Draino,” said one woman who posted to a forum on digestive diseases about the consequences of her lifelong anorexia and bulimia. Some reported cases suggest bulimia may have led to a condition called Barrett’s esophagus, which may can lead to esophageal cancer.

The good news: Many of these complications can be reversible — if the person returns to a normal weight. “The real focus has to be on weight restoration if you want to reverse outcomes,” says Rebecka Peebles, MD, a specialist in adolescent medicine at the Lucile Packard Children’s Hospital in Palo Alto, Calif. “That’s the most essential part of treatment. You can’t wait around for it to happen. It really is an essential first step in treatment and recovery.”

Unfortunately, say experts, too many people believe that anorexia is strictly a psychological disorder, and ignore its medical complications unless the patient becomes visibly, dangerously thin. “A lot of people — parents, and even some doctors — think that medical complications of anorexia only happen when you’re so thin you’re wasting away,” says Peebles. “Practitioners need to understand that a good therapist is only part of the treatment for anorexia and other eating disorders, and that these patients need treatment from a medical doctor as well.”

Studies have found that many people who need treatment for anorexia aren’t getting it. In large part, this may be due to cost. Inpatient treatment can cost more than $30,000 per month, while outpatient treatment can run as much as $100,000 per year.

Melissa Román, a Miami woman who’s been in recovery from anorexia for several years, pays $800 per month out of pocket for therapy sessions that insurance won’t cover. According to the National Eating Disorders Coalition, health insurance companies pay for an average of 10 to 15 treatment sessions for people with eating disorders, when more long-term care — as many as 40 sessions — may be needed for true recovery.

“Access to care is a huge issue,” says Mickley. “Eating disorders aren’t staged the way cancer is, so we don’t have the way to convince insurance companies that a low potassium level can be like a small metastasis. It’s only recently that we’ve begun to understand the genetic and neurochemical basis of anorexia and say that this is a real illness, not a whim of spoiled rich girls. It’s been treated like it’s voluntary and willful as opposed to what it is: a serious, life-threatening psychiatric and medical illness.”