An increasing number of young women are taking selfies to document their weight loss online.
Now, a leading expert has said the growing trend is fuelling dangerous eating disorders.
Dr Alex Yellowlees from the Priory hospital group, the UK’s largest provider of eating disorders treatments outside the NHS, said: “Some people will take repeated pictures of themselves at various stages of their illness, and send them to others.
“They want to keep a record of their illness and see for themselves, as it were, the progress they think they are making towards anorexia, but they will also transmit the images to other sufferers on occasions.”
Yellowlees, medical director and consultant psychiatrist of Priory Hospital Glasgow, said such competitive selfie dieting 'diaries' were contributing to damaging psychological pressures that exacerbate anorexia and other potentially fatal illnesses.
In some cases, Yellowlees said, young women were encouraged to reduce their weight to dangerous levels by looking at so-called “thinspiration” websites where they can compare their bodies with those of other extreme dieters.
Thinspiration websites can include blogs written by extreme dieters who upload their "tips and tricks" to encourage others to lose weight.
Although there has been an attempt by social media companies and internet service providers to crack down on pro-ana (anorexia) sites, Yellowlees warned that many were still active.
“These sites are definitely still active. They may not as prevalent as they were, but they are still an active form of communication," he said.
Some 1.6 million people in the UK are estimated to be affected by an eating disorder, of which around 11% are male.
His warning, ahead of Eating Disorders Awareness Week, came as the Priory Group disclosed it had seen a 15% rise in adult patients admitted with eating disorders in just one year, increasing to 535 in 2014, up from 463 in 2013.
Last year, statistics from the Government’s Health and Social Care Information Centre showed an 8% rise - to 2,560 - in the numbers of NHS-funded patients from the year before entering hospital.
The figures are said to be the tip of an iceberg because many eating disorder sufferers are on waiting lists or never hospitalised.
While "pro-ana" and "pro-mia" (pro-bulimia) websites have existed since the early days of the internet, the growing number of social media sites allowing people to post personal photographs and images has given those with eating disorders a new, international platform.
Smartphone apps also allow users to count calories taken in, and burned, which can escalate the suffering of those with eating disorders who become obsessed with counting the numbers.
Yellowlees added: “Eating disorders are like a form of ‘psychological malignancy’ and should be taken very seriously by society. This includes anorexia nervosa, bulimia nervosa and binge eating disorder. The latter is more common as people get into adulthood and is linked to depression.
"We live in a society which idealises thinness and is obsessed with dieting, size and shape. Society needs to recapture the truth that our real value and worth is not reflected in our clothes size but in our personal qualities and relationships with others."
Eating disorders are both complex and unique, so what should you do if you recognise symptoms in yourself or someone close to you?
In the first instance, eating disorders charity Beat advise suspected sufferers to visit their GP.
"Eating disorders are serious – they claim more lives than any other mental illnesses but they are treatable. The sooner someone gets the treatment they need the more likely to make a full recovery," Rebecca Field, a representative from Beat previously told HuffPost UK Lifestyle.
"If you’re worried about someone, don’t be afraid to approach them – they might be waiting for somebody to reach out. Don’t focus on food or exercising but tell them you’re worried and ask if there’s anything that they need to speak about, or that you’re there if they ever need to talk."
For information and support on eating disorders, visit Beat's website at b-eat.co.uk or call their helpline on 0845 634 1414.