There has been a 15-fold rise in the number of children taking anti-obesity drugs since 1999, but most stop taking them before they have noticed any benefit, new research has revealed.
Researchers believe 1,300 young people are now being prescribed anti-obesity drugs every year, even though they are only licensed for use in adults.
It means drugs such as Xenical, Reductil and Acomplia are being prescribed off-license by family doctors.
The study focused on prescribing data from the UK General Practice Research Database between January 1 1999, and December 31 2006.
Overall, 452 youngsters received 1,334 prescriptions during the study period, and the prevalence of the drugs rose 15-fold among both boys and girls during that time.
Russell Viner, one of the authors of the study, which features in the British Journal of Clinical Pharmacology, said: "It's possible that the drugs are being given inappropriately, or that they have excessive side effects that make young people discontinue their use.
"On the other hand, they could be expecting the drugs to deliver a miracle quick fix and stop using them when sudden, rapid weight loss does not occur."
A Department of Health spokesman said anti-obesity medicines "can help as part of an overall weight management programme".