(CNN) -- Katharine McPhee's revelation that she has battled bulimia puts the American Idol runner-up in the company of millions of Americans.
The National Institute of Mental Health estimates that between 1.1 percent and 4.2 percent of females in the U.S. -- or 1.5 million to 6 million -- suffer from bulimia nervosa in their lifetime. The disorder is increasingly being identified in males as well.
Christopher Athas, a vice president of the National Association of Anorexia Nervosa and Associated Disorders, says one of the many myths about bulimia is that it's a disease primarily of affluent young white women. "That's simply not true," he says. "It's an illness that goes through society." (Watch McPhee talk about her battle with bulimia -- 1:49)
People with eating disorders often have both anorexia nervosa, marked by starving oneself, and bulimia, known as the binge-and-purge disease.
Bulimics eat excessive amounts of food, often feeling out of control, then, out of disgust and a fear of gaining weight, resort to vomiting or laxatives or other extremes. The behavior typically occurs a couple of times a week, experts say. The 22-year-old McPhee told People that for five years, she threw up as often as seven times a day.
Even though bulimics may maintain a normal weight, the disease is often driven by low-self esteem, excessive perfectionism and negative body image. The individual comforts herself, or himself, with food; the late Princess Diana, who also suffered from bulimia, once likened the feeling of post-binge fullness to a hug.
Then the need to purge comes, bringing temporary feelings of relief. But usually, the cycle starts again.
In addition to being potentially deadly (chemical imbalances can cause cardiac arrhythmia and other organ damage) the long-term effects of bulimia aren't pretty. The acid in vomit can erode teeth and the esophagus and inflame glands near the cheeks, so the face can appear swollen.
McPhee says her illness began during her high school years in Los Angeles, where she was always concerned about her appearance. She recalls starving herself and exercising to an extreme. The pattern continued. "I was bingeing my whole life away for days at a time," she told People. She says the bottom came about the time she auditioned for "American Idol."
Concerned that her vomiting was damaging her vocal cords, McPhee decided to get help.
"I entered the program because I wanted to give myself the best shot I possibly could on the show. And, when I did, it was like God put hands on me and said, `I want you to be healed,' " she told People.
McPhee attended group and individual therapy six days a week for three months at the Eating Disorder Center of California in Los Angeles.
Many others who suffer with bulimia don't realize they have an eating disorder and don't seek help. Or, they feel too ashamed to tell anyone. Bulimia is a disease marked by secrecy.
But recovery is possible, says Athas of the anorexia association. "You can get totally well."
It takes recognition of the illness, a genuine desire to get healthy, and usually, he says, therapy, whether individual or group, inpatient or outpatient. Medication can also help control the compulsions.