clenbuterol bodybuilding

Posted 2 years ago

What is clenbuterol and how does it work?

In the bodybuilding world, it is no secret that clenbuterol – more commonly called “clen” – is used to aid with fat loss. In fact, you can be fairly certain that most people competing in an untested federation will have taken clen during their prep. Although its usage is openly discussed with and amongst male competitors, it still remains a huge taboo amongst females. As with most things, this is probably due to a fear of being judged by others for using it.

However, I believe the taboo itself comes from a genuine lack of understanding about the substance. That is, despite clen being incredibly common, many people are unsure of how it actually helps with fat loss, what its mechanisms of action are, and what (if any) are its side effects.

Therefore, the purpose of this article is to discuss the research pertaining to the use of clenbuterol in medical settings, as well as my anecdotal experience. This article is not intended to be used in place of advice or as a recommendation as to whether or not you should use clen during your prep, as that decision is entirely yours to make and the intake of any substance is and will always be your own responsibility.

Medical use and side effects

In medicine, clenbuterol is used to treat people who are experiencing breathing difficulties, such as asthma. Its medical properties enable the muscles of our lugs to relax, which widens our airways, increasing airflow to the lungs and enabling better respiratory function as a result.

However, clen also has properties and side effects that affect our autonomic nervous system, particularly the sympathetic division. This is where and why it becomes popular in the bodybuilding world.

In Layman’s terms, clen essentially stimulates the bodily system that is responsible for eliciting our “fight” or “flight” response. This response is the result of increases in adrenaline levels flowing through blood, which is directly stimulated from the clenbuterol compound. As a result, some of the most commonly reported side effects include (but are not limited to): elevated heart rate; shaking/trembling in the hands; increases in perspiration/sweating; and an increase in body temperature. People who have taken clen may also experience sleep disturbances as a result of its ingestion.

So, with this in mind, I’m sure that at this point you’re probably wondering: “how on Earth does it help with fat loss then?”. Read on!

How it influences fat loss

Now that we’ve established that clen stimulates the production of adrenaline in our bodies, it’s important to know that adrenaline binds to two different receptors in fat cells: the beta receptor (for the purpose of fat loss, we’ll call this “the good guy”) and the alpha receptor (“the bad guy” for the purpose of fat loss). When adrenaline binds to “the good guy”, our fat stores are more readily utilised as a fuel source, otherwise known as “fat burning”. However, when it binds to “the bad guy”, the opposite will happen- no fat burning occurs. If we are trying to get down to low levels of body fat, it follows that we want to elicit as much fat burning as possible – hence why we go into a calorie deficit and increase our energy output.

However, if on top of this we also facilitate the binding of adrenaline to the beta receptors, then our body is in an even more optimal state to burn fat. Furthermore, given that your adrenaline levels will remain elevated for a prolonged period of time, you will actually expend more energy whilst at rest. If we combine this with an increased ability to use fat as a fuel source after taking this compound, it starts to become clear why taking clen is so appealing to athletes.

As a side note, you may have heard me speak about a similar process to this one in my article on yohimbine HCL. In fact, one of its mechanism of action is exactly the same as clenbuterol’s. However, the adrenaline levels that are produced as a result of using clenbuterol will be far more potent/greater than those produced by yohimbine; as such, clen will have a far greater effect on fat burning relative to yohimbine.


In the United Kingdom, it is currently an offence to supply or have an intent to supply Clenbuterol. There is however no possession charge, therefore making its usage not technically illegal.

Clenbuterol is also listed as a WADA prohibited substance. As such, utilising it during the preparation for a natural bodybuilding federation is not permitted, and you would be immediately disqualified if a drug test were to show that you had been using it. In contrast, given the nature of untested bodybuilding contests, its usage is indirectly accepted.

Is it needed?

Each individual has a completely different capacity to lose body fat – some people might find it easy, whereas others may find it very hard. The truth is that for getting stage lean – and especially getting the required level of conditioning that is required to do well – some people could benefit greatly from taking something such as clenbuterol. This is because without it, they might find it very difficult to get body fat levels down to the required level.

Clen can be used to bring in stubborn body fat areas such as the glutes and hamstrings. However, there might be some occasions where even when an individual loses body fat evenly, that the condition that is required for them to step on stage is simple unattainable without lipolytics (fat burners). Sounds unhealthy, right? Correct. But realise that nobody ever said bodybuilding was healthy.

My personal experience

I’ve used clenbuterol throughout many of my own dieting phases and I’ve also used it with clients. I’ve found it to be a very useful tool to help me get down to low levels of body fat. Although the side effects may differ from induvial to individual, my body responds to it just fine. I may get a little bit shaky in the hands for a couple days, but that quickly wears off and before you know it, I barely even notice I’m using it.

A few years ago, I was instructed to take clen in the morning and pre-bed. In hindsight and now knowing the science behind it, this was the worst piece of “advice” I could have been given as it hugely impacted my sleep. I was waking up every hour, and never truly felt rested. However, we live, and we learn. I currently only ever take it and recommend taking it first thing upon wake, so that it is as far from sleep as possible. This has meant that my sleep and my client’s sleep is largely unaffected by this compound.

I have worked with many people over the years who have been very apprehensive about using it, because they have heard “stories”. However, when we follow a safe dosage model and start off small, if they’ve chosen to go ahead, they have all been fine.

I’ve also found it to be very helpful in assisting clients get lean in stubborn areas and without it, some clients would have not been able to get stage-lean glutes, for example. But then again, if you don’t want or need lean glutes, you might be thinking: “what’s the point”. And you are right.

In summary, clenbuterol is commonly used in the bodybuilding world. It aids fat loss by stimulating the fight or flight response in the body and thus, triggers the release of adrenaline in high levels. This elicits some side effects which you should be aware of but overall, under close supervision, I’ve found it relatively safe to use. However, the ultimate choice around its consumption should be yours to make.

Vaughan Wilson Bsc Hons