A new weight loss drug that works by blocking a cannabinoid receptor in the brain has had success in helping people lose weight and keep it off, researchers say.  It also seemed to improve other risk factors for cardiovascular disease.

But critics say the study’s methodology may have been flawed, given that almost half of its lazy pot-smoking participants dropped out.

The drug, called rimonabant, appears to help in maintaining a new, lower weight. In the second part of the study, patients who had received active drug in the first year were then re-randomised for another year. Volunteers taking the 20mg dose in the second year were able to keep off the weight that they had lost; those taking the lower dose or the placebo put some weight back on.