An anti-obesity pill that went on sale in Britain this year has been shown to help people lose weight in the first extensive survey of scientific trials of the drug. The drug, rimonabant, went on sale in June and reduces the craving for food by targeting the same part of the brain that gives marijuana users the munchies.

A review of four controlled trials of the drug found it helped people shed a small amount of weight, less than 4.9kg (11lb) in one year, when they were given a high dosage course of 20mg pills. The review, led by Cintia Curioni at the State University of Rio de Janeiro, reported that only patients on the 20mg pills lost weight significantly. But the high dose pills also brought on side effects, including nausea, dizziness, headaches, joint pain and diarrhoea.

The drug, selling at £55.20 a patient a month, could cause a financial headache for the NHS if it is recommended by the National Institute for Health and Clinical Excellence.