Some 51% of young women would have surgery to improve their looks and a third of those who are a size 12 think they are overweight, a survey suggests.
BBC Radio 1's Newsbeat and 1xtra's TXU asked 25,000 people, mostly aged 17 to 34, how they felt about their bodies.
Almost half the women surveyed said they had skipped a meal to lose weight, while 8% had made themselves sick.
Eating disorder experts said it was "sad but not surprising" that young people felt and acted in such ways.
The survey found two thirds of those who are size 14 also thought they were overweight or fat.
Even with the celebrity emphasis on being size zero (UK size four), fewer than one in a hundred of those surveyed said they were that size.
Given the choice of ultra-skinny, thin and curvaceous, both men and women rated a curvy Martine McCutcheon as having the best body.
Half of the women questioned said there was "lots they would change" about their bodies - and more than 10% "hated" what they looked like.
Many people said they were trying to change their looks.
More than 20% of female respondents said that they were on a diet, compared with fewer than 10% of men.
And more than 50% of female respondents said they would consider having plastic surgery, compared with less than a quarter of men.
Breast enlargement was the most popular operation for women, while liposuction was the next most popular.
Liposuction and nose jobs were the most common choices for men.
The online survey found that even younger people had concerns over their looks.
More than half of girls aged 12 to 16 felt that their body image either stops them from getting a boyfriend or from relaxing in a relationship.
Young men also appear to feel the pressure to look good.
About 20% of those in their early 20s said that they have taken protein supplements in a bid to help themselves bulk up, compared with 11% of over 35s.
And when asked to rate photos of differently shaped male bodies, almost 80% of men and 65% of women favoured a very muscular physique.
Deanne Jade, a psychologist specialising in eating and body image issues, said the problems started with the emergence of thin models, such as Twiggy, in the 1960s.
"I think that was the start of a progression towards increasingly thinner role models. Marilyn Monroe would be trying to diet herself to a size zero if she was on the cinema screen now, which is such a shame."
Dr Terry Apter, a psychologist at Cambridge University, said: "This does signal a great dissatisfaction with the body, a concentration on the body and a sense that there's some ideal which they should reach.
"And they seem to think that if they were just a bit better physically, their lives would be better which is very harmful."
A spokeswoman for Beating Eating Disorders, formerly the Eating Disorders Association, said there were an estimated 1.1 million people in the UK with eating disorders.
She said: "It is sad to read such statistics but not that surprising for us as we receive many calls from the age group mentioned and a lot younger.
"Research says that typical age of onset for an eating disorder is 14 to 25. Young people are affected by many issues at this present time with issues such as exams, bullying, family pressures.
"It's so important for people to develop a healthy perception of their bodies and to raise their self esteem and to develop positive ways of coping with the difficulties that life can bring."