http://www.musculardevelopment.com/articles/fat-loss/599-fat-attack-oct-2002.html
1. Clenbuterol. This drug is a direct beta-agonist, meaning it reacts with the exact same receptors NE uses to stimulate fat loss.1,2 Its main benefit over NE is that it's more specific, attaching only to the beta-2 type receptors. This is important because there are two classes of NE receptors in the fat cell membrane- alpha and beta. The alpha-2 receptors cause the opposite response of the beta receptors in regard to fat loss from the fat cell; alpha-2 stimulation blocks fat release3 while beta stimulation promotes fat release.4 So, clenbuterol is actually a more powerful fat release signal than epinephrine, which stimulates both alpha and beta receptors.
Clenbuterol, which is used outside the U.S. to treat asthma, has been discovered to also be anabolic when used in extremely high doses in animals.5,6 However, the levels needed to achieve this effect would be toxic, likely deadly to humans, so there's no practical anabolic effect from this drug.2 Clenbuterol is typically dosed in the range of 10-40 micrograms (not milligrams) per day, though some users will develop a tolerance to much higher doses.1 The effects of clenbuterol are short-lived, as the beta receptors will down-regulate, or burn out, within a matter of a few weeks, so many users will either use clenbuterol for only a short period or alternately go on and off the drug every couple of days. Clenbuterol has been associated with serious side effects in bodybuilders.7-9
2. Ephedrine/Caffeine Stacks. These supplements have typically been the top sellers for most health food stores, simply because they are effective. Numerous studies have been published demonstrating the combination of ephedrine and caffeine to be effective in accelerating weight loss, often preserving lean mass as opposed to the muscle wasting seen in unassisted fat loss.10,11 An unprecedented amount of controversy has arisen regarding the safety of ephedrine/caffeine supplements due to a number of adverse events reported among users. Ephedrine/caffeine use has been associated with a number of hospitalizations and several deaths.12-14 However, in studies where dosage was controlled and the subjects were monitored, ephedrine/caffeine has been declared to be safe and free from serious adverse events.10,11,15
The adverse reports led the FDA to ban the sale of synthetic ephedrine/caffeine (over-the-counter drugs under the jurisdiction of the FDA), which is unfortunate, as most studies used the more tightly controlled and regulated OTC drugs. However, recent published studies have shown that some of the herbal supplements are as effective and seemingly as safe as the OTC version.16,17 Bodybuilders use ephedrine/caffeine supplements not only for fat loss, but also because it is a stimulant and can aid in maintaining energy and motivation during training.
Unlike clenbuterol, ephedrine does not directly act on the beta receptors, but causes the release of NE, which stimulates both alpha and beta receptors, so the short-term effect of ephedrine/caffeine is not as dramatic as clenbuterol, but the duration of effect is much longer, with ephedrine/caffeine promoting weight loss for at least 24 weeks.10 Doses are typically in the range of 20-25 milligrams of ephedrine and 200 milligrams of caffeine one to three times a day.11,15
