Boys with eating disorders may often be misdiagnosed by doctors, say experts surveyed by the BBC.
George has now fully recovered
Disorders such as anorexia are much more common in girls - only one in ten diagnosed cases are in boys.
Almost half of all child mental health experts asked by the BBC said they felt that more boys were coming forward with the problem.
However, they said that GPs and parents were missing vital clues that boys had developed an eating disorder.
The BBC asked 53 child and adolescent mental health services and children's wards across the UK about the issue.
Some said that they had seen boys as young as eight or nine with the condition.
Almost three quarters of those surveyed said that there was probably under-diagnosis of eating disorders in males.
One said that boys might be more reluctant to come forward: "It's much more socially acceptable for girls to have an eating disorder."
George Ramsay, from Taunton, Somerset, developed an eating disorder at the age of 13, and his weight plummeted to six and a half stone.
He told the BBC: "I always used to be, not fat, but fairly chunky, I wanted to get fit for the rugby season.
George became painfully thin as his illness progressed
"My mother realised I was ill. I thought I was doing well. I thought it was good.
"I cut out fat in my meals - I thought it would make me fat again. I also cut out carbohydrates as well as much as possible."
"At that stage I was drastically ill. My energy levels were zilch. I was sleeping half the day.
"It was very difficult to eat. I could eat, but the feeling afterwards was terrible, I felt so awful.
Eventually he went to his GP to get help, but his condition mystified the doctors.
"There were a lot of tests at the GP - they never even considered I might have an eating disorder.
"When the results came back that there was nothing physically wrong with me, and they didn't really know what to do really."
Eventually, however, George got the help he needed, and has now made a full recovery.