In this article, as part of our Ultimate Series on SARMs, we will consider Ostarine, including its uses and effects. Ostarine is known as the ‘most anabolic’ of all the SARMs, and this is borne out by its typical user base, which includes bodybuilders, strength athletes, and combat sport practitioners.
What is Ostarine?
Ostarine, otherwise known as enobosarm or MK-2866, is a selective androgen receptor modulator (SARM) that was initially developed as a means to combat muscle wastage and osteoporosis, by mimicking the effects of testosterone. Since its creation at the turn of the millennium by GTx Inc., ostarine has been used in a variety of clinical trials for conditions including post-menopausal tissue wastage, tissue wastage in lung and prostate cancer sufferers and even urinary incontinence.
The ostarine molecule (C19H14F3N3O3)
What interests us here, of course, is ostarine’s properties for healthy individuals seeking strength and fitness benefits.
So: can ostarine actually confer such benefits?
The answer is a very firm ‘yes’; but as with all the other SARMs in this series – ligandrol, RAD140, cardarine and andarine – ostarine has specific uses and will suit some more than others.
Ultimately, you must know who you are, and that includes whether you are male or female, and what you want to achieve, before deciding on which SARM to take. You must also be in no doubt of the potential risks and side effects, which we will discuss below.
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The Lowdown — What it Can Do For You
Ostarine is often referred to as the ‘most anabolic’ SARM, and it’s for this reason that bodybuilders, strength athletes (powerlifters, Olympic lifters, strongmen), practitioners of contact sports, martial artists and gymbros are the ones you’ll find taking it.
All of these groups seek the following benefits:
- Loss of unwanted body fat
- Increased lean muscle mass (even in a caloric deficit)
- Increased energy levels
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It’s worth noting right away that, because of its anabolic and performance-enhancing properties, ostarine is a prohibited substance and is listed as an S1 Anabolic Agent on WADA’s prohibited list. A number of athletes have been given bans as a result of testing positive for ostarine. These include:
- UFC fighter Tim Means (2013)
- Boxer Lucian Bute (2016)
- Boxer Alexander Povetkin (2016)
- Triathlete Beth Gerdes (2017)
- Major League baseball player Frankie Montas (2019)
- Cyclist Matteo Spreafico (2020)
Russian boxer Alexander Povetkin, who was banned for ostarine use in 2016
How ostarine works
SARMs induce anabolic activity – growth – by directly stimulating the body’s androgen receptors. These are specific sites within the body to which androgenic (i.e. male) hormones, including testosterone and androsterone, bind.
The activity of these androgen receptors, and the binding of androgens to them, is crucial to the proper expression of male characteristics, including muscle growth and reproductive function.
In the womb, androgens are responsible for sexual differentiation, and then during puberty they regulate the development and function of the penis, prostate and other sexual organs, as well as inducing growth spurts, larynx development and growth of skeletal muscle.
For adults, androgens regulate behaviour, the production of sperm, muscle growth, bone function and aspects of the cardiovascular system.
Androgens regulate sexual function and are responsible, in part, for aggressive behaviour in men. As a result, disregulation or blocking of the androgen receptors can lead to all sorts of conditions.
Ostarine binds to the androgen receptors and mimics the effects of testosterone, increasing protein synthesis and therefore muscle growth.
This is also what steroids do, but SARMs generally have an advantage over steroids, because they only bind to receptors in skeletal muscle tissue.
Steroids, by contrast, work on other tissues in the body and have, as a result, been linked to all sorts of side effects, including prostate and heart problems.
SARMs are also non-aromatising, meaning that they are not converted to estrogen by the body in an attempt to maintain the body’s testosterone-to-estrogen balance.
By contrast, aromatisation can occur when using steroids or testosterone injections, which upset that balance, leading to problems such as gynecomastia (formation of breast tissue) which are ubiquitous among irresponsible amateur lifters.
Although there is no certified research on the use of this SARM for bodybuilding purposes, research in other contexts indicates that ostarine can significantly enhance lean muscle mass for both men and women [R].
Even with a dose as low as one milligram, ostarine can have significant effects.
A study on muscle-wasting in cancer patients showed that a one-milligram dose of ostarine led to a substantial increase in power climbing stairs, and those administered higher doses saw even greater effects [R].
Again, this is strong evidence for ostarine’s muscle-building effects.
Animal trials have also indicated that Ostarine can increase bone density and prevent bone loss, which should be of interest to weightlifters in general, but especially to those who lift heavy weights and are therefore at increased risk of bone injuries including fractures [R].
Of course, it would be strange for athletes and competitors to be taking ostarine, and running the risk of being caught, if it didn’t have the desired effect.
Besides the clinical evidence, there is plenty of anecdotal evidence for the muscle-building effects of ostarine.
It is important to note that anecdotal evidence is often the gold-standard, or the closest to it, that we can achieve in the world of fitness.
As Mark Rippetoe notes, there are no clinical peer-reviewed studies on the effectiveness of a particular dose of the steroid dianabol, but there is a wealth of anecdotal evidence that will tell you what you need to know.
Users report gains of around 5-7lbs of lean mass over a period of six weeks (you should cycle ostarine, see below), as well as increased strength and endurance. One experienced powerlifter on Reddit describes his experience with ostarine thus.
“The first week, I immediately noticed the effects of the drug. At first I thought it was a placebo effect. However, the effect continued- I was not getting sore after my training sessions and I was able to perform significantly more volume work during the training sessions.
“As an experienced lifter, I am not often “de-trained,” so I am seldom “sore” after lifting.
“However, the type of pain I usually feel is fatigue and deep soreness of your body being wrecked from very heavy weight. Sets of 5 at 85% of your 1RM will wreck you.
“With Ostarine, they didn’t wreck me. I really didn’t feel wrecked. I felt like I lifted the next day, sure, but I didn’t have the “hit by a truck” feeling. It was crazy. I couldn’t believe it.”
Although he only took ostarine for a short period, he noticed serious changes within a week.
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Here’s a gymbro’s experience of taking a cycle of ostarine, with lots of photographic evidence.
The anabolic effects of Ostarine are also touted even during a caloric deficit, as demonstrated in the Youtube video. This makes ostarine of interest to people looking to undergo body recomposition (i.e. to lose fat and gain muscle at the same time).
How it Compares to Ligandrol
Ligandrol, like Ostarine, has a very high potency, and doses ranging between 0.1 and 1mg yielded significant results [R].
Animal trials have shown similar results. Ligandrol may increase bone mass and strength, muscle mass and sexual function, without interfering with sensitive areas of the body like the prostate, as steroids do [R].
Total gains over the course of a cycle are generally in the same ballpark as with ostarine. After eight weeks, you can expect to gain 5-7lbs, or perhaps even 10lbs.
In our piece on ostarine, we noted that, in the absence of clinical studies within a bodybuilding or weightlifting context, anecdotal evidence will have to suffice.
In fact, anecdotal evidence is in many ways the gold standard in such contexts, and should not be treated as inferior.
Here are two testimonies, taken from Reddit, from users of Ligandrol.
‘I finally gained 3 pounds after only 2 weeks! Solid mass! All of my max weights have been upped by at least 20 to 30 pounds. I’m hitting weight I’ve never even touched before. My wife straight asked me if I was on roids and I said no but close, sarms.’
Another user wrote:
‘I am now a week into a cycle and have the gains of a month straight of me working my ass off… I’ve got my 6 pack back in a week and all the fat on my stomach that was my original problem is now almost non existent. I will post before after pictures so I may prove the effectiveness of this SARM but damn I’m… elated right now. I’ve recommended it to my skinny brothers as well as I know they will gain and bulk up with just 4 weeks of this supplement. Guys, I’ve taken oral gear before and had gyno [gynecomastia – growth of breast tissue] issues almost immediately. So far no side effects’
A user from the Anabolic Minds forum, who was almost certainly taking a higher dose than the usual dose most users of Ligandrol take, reported the following increases over a period of just a single month.
- 12lbs increase in body weight
- 60lbs increase in squat
- 45lbs increase in bench press
- 60lbs increase in deadlift
- 35lbs increase in standing press
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How it Compares With RAD 140
In a rather bizarre testimonial from Reddit, one user (u/sjswander94) bemoaned the fact that he gained only 10lbs of lean mass on RAD 140 over a period of 8 weeks. Other users were quick to challenge him for claiming that RAD 140 must be ‘overhyped’.
Seriously? What was he expecting – especially as somebody who, by his own admission, had been lifting for six years already and wasn’t really eating much more than his maintenance calories?
SARMs aren’t steroids, and are used at lower doses, generally, than steroids; indeed, considering the low doses that are used, SARMs pack a serious punch, milligram for milligram. u/sjswander94 noted that the ‘side effects were minimal’.
Another user, who was running a stack of SARMs including RAD 140, noted that ‘he reliably put on a pound of muscle each week with a 500 calorie daily surplus and 8 hours in the gym each week.’
In the previous articles on Ostarine and Ligandrol, we posted two videos from a gymbro Youtuber (russolifts) who has used various SARMs as part of his supplement regime.
He reported significant gains – in his opinion greater than with Ligandrol – over a period of six weeks, despite by his own admission eating a bad diet. He also claimed that RAD 140 was the only SARM of the three to give him significant strength gains as well.
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How to use Ostarine
Ostarine, like the other SARMs, is administered orally. There is no need to inject it, as you would steroids or other compounds like human growth hormone.
The best way to use ostarine is in a cycle of six to eight weeks. This will give you significant gains and then allow your body, including your body’s testosterone levels, to recover.
While studies have reported significant effects as a result of even small doses of ostarine – as low as one milligram (see above) – the more you take, the greater the effects. However, it should be noted that the more you take, the greater the side effects will be. As is well known, this is also the case with steroids; although even at higher doses, SARMs will not have the same side effects as steroids.
Potential Side Effects
The side effects of ostarine are much milder compared to those of traditional androgenic agents including steroids. One study of muscle wastage noted no negative side effects associated directly with the use of Ostarine [R].
Other studies, however, have suggested that there may be changes to the user’s blood profile, especially to cholesterol levels, and that levels of liver enzymes may increase, a sign of increased strain on the liver.
Others have reported reduced sex drive, hair loss, acne and mood swings, but it’s not immediately clear whether these symptoms are a result of the SARMs themselves or of other ingredients included with them [R].
Some of these symptoms are clearly associated with reduced natural testosterone levels.
As with steroids, the use of Ostarine will reduce natural testosterone levels. The reduction will correspond with the amount of Ostarine you take and for how long. You may notice some visible shrinkage of the testicles.
As a result, after a cycle of Ostarine, it may be wise to engage in a round of post-cycle therapy, as many steroid users do.
Note, though, that because the side effects, at least in the short term, appear to be much less serious than for steroids, the post-cycle therapy will almost certainly need to be less severe.
Post-cycle therapy helps to restore your natural testosterone levels, and may last up to six weeks.
Various supplements and medications are available, which we will discuss in a separate article on SARMs stacks. You can begin post-cycle therapy as soon as you stop taking SARMs.
The longer term effects of SARM use are, at this stage, unknown and it’s worth reiterating that SARMs aren’t legally certified as a dietary supplement.
You are taking a risk if you use them; but you are also taking risks lifting heavy weights, running – or even just stepping outside your front door.
Ultimately, it is a decision for you to make, based on willingness to balance the risk against the potential rewards.
Is Ostarine Present in Other Supplements?
Generally, no. In large part, this is because SARMs are not approved for human consumption in the US or any other country. As a result, there are no legal medications or dietary supplements that contain SARMs, and that includes ostarine.
However, in certain cases it appears that some supplement manufacturers have put SARMs – illegally – into their supplements and labelled them as ‘legal steroids’ or chemicals for ‘research purposes only’.
Manufacturers may also omit Ostarine from the list of ingredients or give it a different or misleading name. Ostarine also goes by the name of enobosarm, MK-266 and GTx-024.
If you have any doubts about a supplement, first consult the label and then, if you are not convinced, check the USADA’s Supplement 411.
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Ostarine MK-2866 FAQs
Is Ostarine MK-2866 safer than steroids?
Yes, Ostarine MK-2866 is much safer than anabolic steroids due to it’s selective nature.
Does Ostarine MK-2866 Build Muscle?
Yes, Ostarine MK-2866 does help with building muscle (and not just shredding fat).
Does Ostarine MK-2866 Burn Fat?
Yes, Ostarine MK-2866s primary function is burning fat.
Is Ostarine MK-2866 Legal?
Ostarine MK-2866 is legal to be bought and sold as a product, but not legal for human consumption.
Does Ostarine MK-2866 Require a PCT?
Yes, Ostarine MK-2866 requires a PCT. You need one to restore your natural testosterone production.
Can I Stack Ostarine MK-2866 With Other SARMs?
Yes, Ostarine MK-2866 is stackable with other SARMs.
What is the Dosage for Ostarine MK-2866?
Ostarine MK-2866 should be dosed at 15-25 mg a day.
How long do I run Ostarine MK-2866?
You should run Ostarine MK-2866 for 8 weeks.
What are the known Ostarine MK-2866 side-effects?
Ostarine MK-2866s side effects are: oily skin/acne, higher estrogen, liver toxicity and higher blood pressure.
Ostarine MK-2866 User Reviews?
“Ostarine is a very versatile SARM that can be used to build muscle, lose fat, increase strength, and transform your body. Ostarine can be used to accelerate muscle growth while bulking, and it can also be used to keep muscle mass while on a cutting cycle.”
Disclaimer: we are not medical professionals. If you wish to consume SARMs and/or other performance enhancing drugs, we urge that you take the appropriate channels and consult your physician. Please ensure that you request comprehensive bloodwork to protect your health, under the care of your physician.
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