People tend to think of anorexia and bulimia as female-only disorders, but a growing body of evidence suggests the psychological illnesses are now affecting boys and young men in alarming numbers as well.

According to the National Eating Disorders Association, at least one million males in the United States have anorexia or bulimia. What’s more, those numbers may not even be accurate — experts say boys and men often feel so much shame about having an eating disorder that they go unaccounted for, NBC News Reports.

While previous estimates said only one in 10 sufferers of anorexia or bulimia were male, a 2007 study done by Dr. James Hudson, a Harvard psychiatry professor who specializes in eating disorders, said males account for one in four cases instead — a far higher number.

“It appears that the prevalence of the disorder is increasing among boys,” he told MSNBC. “It may be that boys are simply more comfortable coming forward now than in the past.”

Dr. James Lock, a psychiatrist at Lucile Packard Children’s Hospital, said, “Boys don’t get identified … They come later to treatment [so they've] therefore had a longer time to lose weight [and are] physically sicker. Sometimes that’s allowed the psychological processes to be more reinforced in their own thinking and the behaviors.”

Oddly enough, experts say the increased focus on childhood obesity could be partially to blame for a rise in eating disorders among both boys and girls.

“The emphasis in our culture about eating healthier is no doubt the biggest factor,” said Dr. Jennifer Hagman, who runs the eating disorder program at Children’s Hospital Colorado. “In school they’re telling them to limit the fat in their diet. I hear from many kids in the program that it was after a health class that they started to limit their diets.”