A new weight loss drug that works by blocking a cannabinoid receptor in the brain has had “modest” success at helping people both lose weight and keep it off, researchers say. It also seemed to improve other risk factors for cardiovascular disease beyond what would be expected from weight loss alone.

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

Although 3045 people entered the study, the main results were based only on the 1602 who followed through to the end of the first year. “That may erroneously create a larger effect,” says Denise Simons-Morton, at the US National Heart, Lung and Blood Institute in Bethesda, Maryland, who co-wrote an accompanying editorial about the paper. She and her co-authors suggest the researchers should have made a greater effort to measure final outcomes in all their participants, even those who left early.

Read more about study findings regarding the Acomplia weight loss drug at http://www.newscientist.com/article.ns?id=dn8724.