Losing fat/cutting: Clenbuterol

Losing fat/cutting: Clenbuterol

Many people want to strip away fat and for many this means use of a drug when cardio just will not get you shredded enough.

Clenbuterol is a popular drug that is used by bodybuilders before competitions, however, with many drugs there are side effects.

LAST UPDATED: April 2019 by Ben.

This review contains cited studies found at the bottom of this page.

What is Clenbuterol?

Clenbuterol is a potent and long lasting stimulant and thermogenic (i.e it raises your body temperature) drug.

It causes an increase in aerobic capacity, central nervous system stimulation, blood pressure, and oxygen transportation.

It increases the rate at which body fat is metabolized while increasing the body’s basal metabolic rate (BMR).


As Clenbuterol is a strong stimulant the side effects of Clenbuterol can be very strong, and they will generally affect most people in one way or another.

The most common side effects surround a jittery or wired feeling, shaky hands and increased sweating.

However, more importantly or rather, more concerning it has been known to cause at least two documented heart injuries. [1]

Most all who use Clen will experience such effects to a degree, but they will commonly be very pronounced during the early stages of use.

As the individual becomes accustomed to the stimulant, such related effects should begin to subside, but they will be so strong in some people that some will not be able to use it.

It is worth noting that there have been many high profile sports suspensions and bans from use of Clenbuterol and it is a controlled substance so if you are involved in competitive sports it would be wise not to take it. [2]

clenbuterol compound

Side Effects

While it features on the WADA list of banned substances there are some potential serious health implications to using clenbuterol that must be raised.

So, what are the dangers identified by clinical studies?

The way we must approach clenbuterol is that it is similar to amphetamines and has similar effects.

Amphetamines are well known appetite suppressants and also increase energy levels for up to eight hours while making you feel euphoric.

However, amphetamines can also cause a number of unwanted side effects, particularly as the drug wears off.

This can include exhaustion, feelings of depression, irritability, convulsions and even death.

Furthermore, because amphetamines curb appetite it can mean that you are not getting the nutrients that are required for a healthy body. [3]

How does Clen work?

Clenbuterol is also a central nervous system stimulant and classified as a ‘beta-2 agonist’.

It also increases the heart rate, your body temperature which causes excess perspiration, and it also increases your blood pressure.

All of which can lead to health problems, particularly the cardiovascular risks as already mentioned.

Psychological Effects

But there’s more psychological issues that are often not covered. Such as anxiety and nervousness coupled with restlessness. [4]

Furthermore, there have been reports of meat contamination that has entered the food chain when it has been used illegally to increase the size of animals to yield more meat.

In the 1990’s over 100 people were declared unwell after consuming beef liver contaminated with clenbuterol in Spain.

In the same decade there was a second incident in Spain and a case in France affecting people who ate beef liver which left people suffering from tremors and tachycardia for 3 days.

This wasn’t just a European problem. Residents of Hong Kong were also falling ill during 1997-1998 due to eating pork products and suffering from clenbuterol toxicity.

These patients experienced a number of symptoms including:

  • Muscle tremors
  • Dizzieness
  • Vertigo
  • Heart palpitations
  • Myalgia (muscle pains)
  • Fever
  • Chills
  • Confusion
  • Muscle weakness

Clenbuterol is absorbed well by the body and up to 80% is bioavailable while being able to stay in the body for days rather than just hours. [5]


Female squatting and male spotting in the gym

With all of these documented findings, you may be hard pressed to consider that there are any benefits to using clenbuterol.

However, there is evidence available that demonstrates it has capabilities to decrease fat levels and increase anabolic effects.

The evidence for the latter is overwhelmingly based on animal testing.

However, it is also used to help alleviate any bronchial issues people may be suffering from.

Fat Loss

Interestingly clenbuterol’s fat loss effects on rats was dependant on their body composition.

For those lean rats fat levels were unaltered, however, obese rats saw a significant reduction of fat mass due to a increase of thermogenic effects. [6]

Furthermore, patients recovering from cardiac failure saw few ill effects of clenbuterol administration but an increase of lean mass and an improvement of lean mass/fat mass ratio. [7]

Being a Beta agonist, substances like clenbuterol and clenbuterol itself can dramatically reduce fat mass while simultaneously promoting muscle development, hence, its use in agriculture. [8]

Muscle Mass

Not only has clenbuterol demonstrated its ability to reduce adipose tissue but also increase muscle mass.

A particular concern is muscle wastage for the elderly and those recovering from surgery. Clenbuterol has induced muscle growth and prevented muscle waste when tested on rats of varying ages to provide an inclination of how it may effect human subjects. [9]

While this looks positive, when clenbuterol has been administered to human patients it was noted that overall lean skeletal muscle mass but had no positive effect on endurance levels. [10]

Interestingly the increase of muscle growth were still evident even with a hypocaloric diet of up to a 50% calorie deficiency. [11]


Clenbuterol has proven its abilities to surpass an alternative complex of theophylline and ethylenediamine to alleviate wheezing and relax the airways for those suffering from asthma.

The Aminophylline complex is an excellent drug used to relieve bronchial spasm and improve breathing which is commonly prescribed. [12]

However, clenbuterol exceeded the effects of Aminophylline on the longevity scale and particularly for night time wheezing. [13]

Take Home

As with most drugs there is an element of associated risk. More so if self administered ad not by a medical professional.

Clenbuterol does have some benefits, particularly for those looking to increase physical performance and improve their aesthetic appearance by modern perceptions.

Hence why it is a popular drug for those looking to increase muscle mass, cut fat and physical exertion.

However, there are a long list of unwanted and negative side effects that can have serious health implications that have been outlined.

These risks can be exacerbated by ‘stacking’ other drugs also used to help improve body composition. [14]

People who are suffering from or develop cardiac and liver abnormalities are particularly vulnerable and caution must be taken.


[1] A descriptive study of adverse events from clenbuterol misuse and abuse for weight loss and bodybuilding. Spiller HA, James KJ, Scholzen S, Borys DJ. Subst Abus. 2013;34(3):306-12. doi: 10.1080/08897077.2013.772083. PMID: 23844963

[2] https://www.wada-ama.org/en/questions-answers/prohibited-list-qa#item-386

[3] http://publications.msss.gouv.qc.ca/msss/fichiers/2009/09-804-08A.pdf

[4] http://www.nationaldrugstrategy.gov.au/internet/drugstrategy/publishing.nsf/content/1A9A66204FD341EDCA2575B4001353AA/$File/fs_clenbuterol.pdf

[5] Veterinary Toxicology, Basic and Clinical Principles. Ramesh C. Gupta.

[6] Influence of clenbuterol on energy balance, thermogenesis and body composition in lean and genetically obese Zucker rats. Rothwell NJ, Stock MJ. Int J Obes. 1987;11(6):641-7. PMID: 3440683

[7] Clenbuterol increases lean muscle mass but not endurance in patients with chronic heart failure. Kamalakkannan G, Petrilli CM, George I, LaManca J, McLaughlin BT, Shane E, Mancini DM, Maybaum S. J Heart Lung Transplant. 2008 Apr;27(4):457-61. doi: 10.1016/j.healun.2008.01.013. PMID: 18374884

[8] Multiple actions of beta-adrenergic agonists on skeletal muscle and adipose tissue. Yang YT, McElligott MA. Biochem J. 1989 Jul 1;261(1):1-10. Review. No abstract available. PMID: 2570567

[9] Effects of clenbuterol on skeletal muscle mass, body composition, and recovery from surgical stress in senescent rats. Carter WJ, Dang AQ, Faas FH, Lynch ME. Metabolism. 1991 Aug;40(8):855-60. PMID: 1861634

[10] Clenbuterol impairs muscle quality and is potentially dangerous. Habedank D, Steeg M, Anker SD. J Heart Lung Transplant. 2008 Aug;27(8):934-5. doi: 10.1016/j.healun.2008.05.002. Epub 2008 Jun 25. No abstract available. PMID: 18656813

[11] https://www.sciencedirect.com/science/article/pii/002604959090034A

[12] https://bnfc.nice.org.uk/drug/aminophylline.html

[13] Clenbuterol (“Spiropent’): a long-acting bronchodilator. Wheatley D. Curr Med Res Opin. 1982;8(2):113-9. PMID: 7049586

[14] Performance-Enhancing Drugs Abuse Caused Cardiomyopathy and Acute Hepatic Injury in a Young Bodybuilder. Li C, Adhikari BK, Gao L, Zhang S, Liu Q, Wang Y, Sun J. Am J Mens Health. 2018 Sep;12(5):1700-1704. doi: 10.1177/1557988318783504. Epub 2018 Jun 21. PMID: 29926766

Fat cutting with clenbuterol
Article Name
Fat cutting with clenbuterol
We look at how clenbuterol can help you cut fat, but also the risks.

Ben BA(Hons), PGCert

Ben established this site to be a free resource in 2015. Since then it has gained over half a million visits. He has always been interested in sport and he started playing rugby at the age of 6 represented his town, county and school. Ben also enjoys cycling, has started skiing and is in the Army Reserve representing his Regiment as part of the 150 Regimental Shooting Team. He holds a bachelor's and postgraduate degree in sport exercise & nutrition.
Verified by MonsterInsights