Almost a third of British teenagers feel ashamed of their body, with imagery of "idealized" bodies on social media driving their insecurity, new research has found.
The same number of young people have their habits in an effort to age how they look, a survey of teenagers for Mental Health Foundation (MHF) shows.
Experts said the results were alarming, especially because body image anxiety can trigger self-harm and suicidal thoughts in teenagers.
The findings prompted calls for advertisements for weight loss and cosmetic surgery to be voted on.
"Our survey has shown that millions of young people in Britain are worrying about their body image," said Jane Caro, the foundation's lead program for families, children and young people. "Worries about mental health problems and, in some instances, are linked to self-harm and suicidal thoughts and feelings."
Overall, 31% of 13- to 19-year-olds feel ashamed of their body shape, according to the YouGov survey of 1,118 British teenagers, which was weighted to represent everyone in those ages. Slightly more – 35% – had stopped eating or limited what they were because they were worried about their body.
In addition, 35% of respondents worried about their body often or every day, 37% felt upset and ashamed about it and 40%. Two in five said they had seen each other on social media.
Research has shown that people are dissatisfactory with others. The MHF said: "Exposure to idealized bodies in the media and social media provides significant risk of this and internalising" ideal "body image that is unrealistic or unattainable."
Experts in children's mental health media is a key factor in the growing numbers of teenagers needing care because they have anxiety and / or depression or self-harm. The number of teenagers needing hospital treatment after trying to kill them.
"These alarming results show what a significant issue. Emma Thomas, the chief executive of Young Minds, said: "It's clear that they look like images of 'perfect' bodies.
The MHF wants the Advertising Standards Authority to pre-vet broadcast advertisements that may damage someone's view of their body, as well as ads for cosmetic surgery and weight loss.
NHS England has called for a mental health service for under-18s.
"We know that appearance is one of the things that matters most to young people. These findings are not clear, "said Claire Murdoch, its national director for mental health.
"While the NHS long-term plan is dramatically expanding mental health services to hundreds of thousands more people, it is time for industry and society to listen to and act when teenagers say mental ill-health in their generation. "
Thomas said the forthcoming new relationships and health curriculum in state schools in England from September needed to help "the young people learn to recognize the images they look at on social media may have edited, curated highlights of people's lives – and that unrealistic standards of ' beauty 'are not achievable for most people ".
• In the UK, Samaritans can be contacted on 116 123 or email firstname.lastname@example.org. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at www.befrienders.org.
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