May 7 (HealthDay News) -- Because they're accustomed to diagnosing eating disorders in white teenage girls, doctors may overlook the condition in boys and certain ethnic groups, U.S. researchers warn.

A team at the Stanford University School of Medicine and Lucile Packard Children's Hospital, in California, noted that making this diagnosis can be especially difficult when patients don't display the typical symptoms of eating disorders.

"We need to think more broadly about who struggles with eating disorders," Dr. Rebecka Peebles, an adolescent medicine and eating disorder specialist, said in a prepared statement.

She noted that diagnostic and treatment criteria were designed with white females in mind and that doctors "may not be asking the right questions for these other groups at all."

In one study of 104 boys, ages 8-19, and 1,004 girls with eating disorders, Peebles found that the boys were less likely to use purging behaviors, such as vomiting or the use of laxatives, to control their weight -- 23.5 percent of boys and 32.4 percent of girls.

The study also found that boys were more likely than girls (62.2 percent vs. 49.1 percent) to be diagnosed with an "Eating Order Not Otherwise Specified" (EDNOS), rather than with anorexia or bulimia. The fact that boys tend to express themselves differently may be a factor.

"We're taught to be alert for patients who express a desire to be thin. But clinically, boys often talk about wanting to be more fit and eat healthy, which doesn't set off the same kind of alarm bells," Peebles said.

In a second study, she used a Web-based questionnaire to survey people who visit Web sites about eating disorders. Peebles found that American Indians and Alaskan Natives were much more likely than whites to use laxatives to control weight, and that almost 47 percent of people in these two groups had been hospitalized at least once as a result of eating disorders, compared with about 13 percent of whites.

American Indian and Alaskan Native respondents also reported a longer duration of disordered eating than other groups and had higher maximum lifetime weights and lower minimum lifetime weights, which suggests more dramatic swings in body weight, Peebles said.

The research was presented at this week's International Eating Disorders Conference in Baltimore.

SOURCE: Stanford University, news release, May 3, 2007