The first clinical studies of an experimental drug have revealed that obese people who take it for 12 weeks lose weight, even at very low doses. Short-term studies also suggest that the drug, called taranabant—the second drug designed to fight obesity by blocking cannabinoid receptors in the brain—causes people to consume fewer calories and burn more, researchers report in the January issue of Cell Metabolism, a publication of Cell Press. Cannabinoid receptors are responsible for the psychological effects of marijuana (Cannabis sativa), and natural “endocannabinoids” are important regulators of energy balance.