Almost one in ten girls have taken diet pills, weight loss supplements or laxatives in the past year, according to a survey.
Researchers evaluated data from 604,552 children aged 18 and under who took part in 90 separate studies from different countries.
Diet pills were found to be the most commonly used weight-loss product among teenagers, followed by laxatives and diuretics.
Around 5.3 per cent of children from both sexes used non-prescription weight loss products, the study found.
The use of weight loss products was significantly higher in girls than boys, with nearly one in ten adolescent girls found to have used a weight loss aid in the past year.
Researchers said the findings were a "public health concern" because of the link between use of weight loss products and low self-esteem among girls, as well as "parental influence to lose weight" and "media or social media influences promoting unrealistic beauty standards".
The use of weight loss products was "significantly higher" in North America compared with Asia and Europe.
Nonprescribed weight loss products are not recommended for children as they pose safety concerns and are linked to unhealthy weight gain in adulthood. They have also been found to increase the chances of developing an eating disorder within several years of onset of use.
The authors, led by the School of Public and Preventive Health at Monash University in Melbourne, said: “Non-prescribed weight loss products in children are not medically recommended for healthy weight maintenance as they do not work, are dangerous, are associated with unhealthful weight gain in adulthood, and increase the risk of being diagnosed with an eating disorder within several years of onset of use.
“Furthermore, childhood use of non-prescribed weight-loss products has been associated with low self-esteem, depression, poor nutritional intake, and substance use.”
They added: "These findings suggest that, given the ineffectiveness of these products for weight loss coupled with their harmful long-term health consequences, interventions are required to reduce use of weight-loss products in this group."
Figures published last year showed that children and young people in London with an eating disorder face the longest wait for treatment following a routine referral of any region in England.
Tom Quinn, director of external affairs at eating disorder charity Beat, said of the study: "We’re incredibly saddened and alarmed that so many children and young people have been able to access diet pills and laxatives.
“There’s an enormous pressure on young people to lose weight, and we often hear from people who are struggling with low self-esteem and body image as part of their eating disorder.
“Weight loss medications are very dangerous, especially if taken without a prescription, but the promise of ‘quick results’ is often very attractive to people with eating disorders even if it harms their health.
“There must be stricter laws to ensure that weight loss products are never sold to people with or vulnerable to an eating disorder."
