The nation's first anorexia nervosa study found that 26 children have died from the eating disorder and that 944 children went to hospitals last year complaining of its symptoms.
Some of the patients had taken their own lives, according to the study released Tuesday.
The nationwide study, conducted by the Japanese Society of Psychosomatic Pediatrics, is the first formal research here on the issue.
The study drew responses from 294 of 569 pediatrician-training hospitals but did not specify the patients' age or sex.
Of the 294 hospitals, 24 said that a total of 26 children died after seeking help for weakness or heart problems. The time frame was not specified. Some of the 26 killed themselves.
Of the 944 patients who sought help last year, 358 came to the hospitals for the first time and the remainder had seen doctors before.
"I'm surprised to see the large number of the patients who died. We need preventive education," said University of Tsukuba professor Shinya Miyamoto, who led the research.
People with anorexia nervosa have a fear of getting fat and refuse to maintain normal weight. To reduce weight, they eat less, vomit or use laxatives after eating.