Clenbuterol is used by athletes and bodybuilders for it’s ability as a beta-2 agonist. It therefore stimulates your beta-2 receptors, which in turn help you to lose fat by allowing your body to release and burn more stored fat. Clen has been used for literally decades in the foreign veterinary world, for increasing the lean yield of livestock. It is clearly a very effective agent for this purpose, although its long half life and tendency to stay active in the body for long periods of time mean that vets in the United States aren’t able to use it. This is also the reason why (although it’s an asthma medication) it’s not available to asthmatics in the US of A. But in the world of athletics, Clenbuterol has a much longer history of use.