Six out of 10 young people with eating disorders don't ask for any help for at least six months, says a report by the Eating Disorder Association (EDA).
The survey of 1,000 young people with conditions like anorexia and bulimia found that 45% said they felt they could not talk to their parents.
And one in five said parents noticed they were unwell before they did.
The EDA said it is really important to get help quickly, as this improves your chances of getting better.
One in four of the young people questioned also said they thought the media should show more 'real' bodies.
And many also said magazines should stop praising thin celebs and printing lots of articles about dieting.
Around 1.1 million people in the UK suffer from an eating disorder, and people aged 14-25 are most at risk of suffering from the condition.