Does Marijuana Affect Muscle Growth?

Although marijuana is deemed illegal, unethical, and or dangerous to the health by many circles in society, there are others who embrace it for relaxation, inspiration and social bonding. Some in the bodybuilding world strictly avoid marijuana use because they think it is detrimental to their workouts, while others swear by it as a tool that provides focus and added force to exercise routines.

Regardless of which side of the fence you happen to sit on, this article will try to address the affects marijuana may have on muscle growth through scientific studies. Admittedly, there is not a great deal of substantial evidence or research to determine black and white boundaries, but a chunk of the evidence that is available is shared here.

THC and Testosterone

In marijuana, d9-THC is the ingredient that has a psychoactive interaction with the brain and produces the “high” experienced when consumed. Since testosterone is one of the primary anabolic hormones responsible for muscle growth and repair then understanding if and how THC affects testosterone production is worth looking into.

Study No. 1 – Animal

A study published by the Journal of Clinical Pharmacology (2002; 42:90s-96s) revealed that THC affected growth hormone (GH) production in lab mice. It was determined that GH blockage was attributed to the THCs ability to cause the hypothalamus (located above the pituitary gland and responsible for prompting growth hormone secretion by releasing Growth Hormone Secreting Hormone, or GHRH) to trigger the release of a chemical known as somatostatin (SS). Somatostatin is the substance the body uses to stop GH secretion.

The conclusion of this study, therefore, was that cannabis usage does hinder the release of growth hormones (at least in lab mice). However, it was also revealed that when the mice were subjected to long-term exposure of THC, the hindering affects wore off over time. The theory is that the CB1 receptors in the brain eventually become accustomed to the THC chemical and become less responsive to its affects.

Study No. 2 – Human

Study results were released in 1986 from Pharmacol Bochem Behav (June; 24(6):1749-54) – Acute effects of smoking marijuana on hormones, subjective effects and performance in male human subjects which took 4 non-smoking males and gave them joints (1 or 2) containing 2.8% THC in total during 2 separate days. Blood tests revealed a significant drop in LH (luteinizing hormone) which stimulates testosterone production and a slight drop in overall testosterone levels (although they remained in the normal range). Tests also revealed a slight elevation in growth hormones (GH) and cortisol (which breaks down protein to be used as glucose). Cortisol is also regulated by the hypothalamus which, as we saw in the lab mice study, is affected by the THC in marijuana. However, it should be noted that the subjects of this study were not regular marijuana smokers.

Study No. 3 – Human 

This study released in 1975 by the American Journal Alcohol Abuse (1975;2(2):269-75) entitled Plasma testosterone levels in healthy male marijuana smokers sheds a bit more light on the effects of marijuana on regular users. Blood samples of 25 male college students were examined who smoked approximately 5 joints a week on average. Those samples were compared to those of 13 non-smokers. Testosterone levels were revealed to be normal for that age group even though they were regular marijuana smokers with no differences observed when compared with the control group. This, again, seems to demonstrate that any hormonal changes caused by THC in “occasional” users eventually regulate to normal levels in regular users.

Study No. 4 – Human

A more recent study released in 1991 utilized 93 males and 56 females. Half the group was divided into marijuana usage levels of infrequent, moderate and frequent. The other half were non-smokers and used as the control group. Again, there were no detectable changes in hormone levels between any of the groups regardless of the amount of marijuana used or not used.


Based on the human studies of the affects of marijuana on muscle growth, it appears that there is no measurable level of hormonal change resulting from THCs affect on human growth hormone (HGH) systems and testosterone in particular. Any small changes which occurred in “first time” or “occasional” smokers appear to regulate with continued use.

Weight Gain 

One area where the affects of marijuana on weightlifters, bodybuilders and fitness models is evident is in diet. Those who smoke marijuana experience what is termed “the munchies” by such users. The THC in marijuana also affects the hunger mechanism of the brain which triggers an increase in appetite.

The problem is that the foods which are normally craved are sweets and other high-calorie foods. Someone with the munchies generally resorts to a gluttonous state of consuming junk foods which are void of much nutritional value. Because calories are converted into fat for future use, body fat can be quite high in marijuana users. Several studies conducted by the National Cannabis Prevention and Information Centre of Australia have come to this conclusion.

Weightlifters who are concerned about putting on bulk may benefit from marijuana use. However, unless appetite is controlled and nutritious foods are consumed instead of junk foods, bodybuilders and fitness models who use marijuana may find that they are constantly involved in a battle of the bulge.

Bottom Line

It appears that the majority of testing conducted on marijuana and how it affects muscle growth reveal that it basically doesn’t affect or, at least, has a very insignificant affect. This seems to be even more true for those who are regular users.

However, there are other health risk factors which should be looked at and it all boils down to personal preference at this point in the research game. Some people swear by getting high before a workout. They say that it helps them to focus intensely on their weight training and causes them to push harder than they normally would if not high. Others report vomiting and sluggish, lazy behavior that prevents them from completing intense workouts or workouts at all.

Basically, if you don’t smoke marijuana then there is no good reason to begin. If you smoke it and think it hinders your workout performance then stay away from it on days you hit the gym. If you smoke it and believe you receive fitness benefits from the high then have at it! Just make sure to chow down on healthy foods when the munchies hit!

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