YK-11 vs Ostarine: what to choose and for whom

The question “what to choose: YK-11 or Ostarine” is one the editorial team receives regularly. The honest answer is uncomfortable: for a healthy person who trains, both substances are a choice between a known risk and an unknown one. Below we discuss how to think about such a choice, for whom the risks are highest and what actually works for building muscle and recovery.

Why the question “what to choose” is posed incorrectly

When people compare two substances, they usually assume that both are legitimate options and that the only difference is in effectiveness or convenience. In the case of YK-11 and Ostarine this premise is false. Neither substance is registered as a medicine, neither has an approved indication, and both are banned by the World Anti-Doping Agency.

Ostarine (enobosarm) has at least gone through clinical studies: we know that in elderly people and patients with cachexia it modestly increased lean mass, and that it also lowered HDL and suppressed one’s own testosterone. For YK-11 there are no such data at all — neither on effectiveness nor on safety in humans.

So it is more correct to ask a different question: is there a situation in which the risk of an unregistered substance is justified by the expected benefit? For a healthy person who wants to improve their physique or strength, the editorial team does not see such a situation.

An additional layer of the problem is the actual content of the product. Independent analyses of SARMs sold online have shown frequent discrepancies with the label. So even having “chosen” Ostarine, the buyer has no guarantee of getting exactly that and exactly in the declared amount.

Risk matrix: what is known and what is not

It is convenient to break the comparison down along two axes: how well the substance has been studied and how serious its known problems are. Ostarine ends up in the “partly studied, with confirmed side effects” zone. YK-11 is in the “almost unstudied” zone, where the very absence of data is a separate risk.

Supporters of YK-11 often cite its “anti-myostatin” mechanism via follistatin as an argument. But this mechanism has been shown on C2C12 cells in a laboratory dish. Between such a result and a safe effect in humans lie preclinical toxicology, pharmacokinetics and several phases of clinical studies, none of which YK-11 has passed.

The steroidal structure of YK-11 also matters: it brings it closer to classic anabolic steroids in its possible risks to the liver, lipids and hormonal axis. The notion that “SARMs are milder than steroids” cannot be applied to it.

For Ostarine, the known risks include lowered HDL, suppression of testosterone and described cases of drug-induced liver injury in people who took SARMs on their own, often at doses and durations exceeding those in studies.

For whom the risks are highest

There are groups of people for whom even a theoretical discussion of a choice between these substances makes no sense, because the risk far outweighs any possible benefit. The editorial team highlights several such categories.

For athletes the situation is complicated by the fact that Ostarine is often found in contaminated supplements. So the risk of disqualification exists even for those who knowingly took nothing prohibited. This is one more argument in favor of certified products.

For women, SARMs are sometimes positioned as a “safe alternative” to steroids. This is a dangerous oversimplification: selectivity in humans has been measured only for particular substances and only at certain doses, and for YK-11 it has not been measured at all.

Finally, people with chronic diseases risk an interaction with medicines that no one knows about, because such studies have simply not been carried out.

What works instead

If the goal is building muscle mass, the greatest impact comes from the basics: progressive strength training, sufficient protein, energy balance and sleep. The ISSN position stand on protein (Jäger et al., 2017) recommends 1.4–2.0 g of protein per kilogram of body weight per day for people who train — a legal and safe lever that most people underuse.

Among supplements, creatine monohydrate has the best evidence base. The ISSN position statement (Kreider et al., 2017) summarizes numerous studies in which creatine combined with training enhanced gains in strength and lean mass with a good safety profile. The standard maintenance dose is 3–5 g per day.

• Progressive strength loading 2–4 times a week with attention to technique.
• Protein 1.4–2.0 g/kg/day, spread across several meals.
• Creatine monohydrate 3–5 g/day.
• Sleep 7–9 hours and control of overall load.
• Supplements with independent certification for the absence of doping substances.

If, however, the issue is a medical problem — loss of muscle mass due to illness, age or low testosterone — the decision should be made by a doctor on the basis of lab tests. For confirmed hypogonadism there are registered treatment methods with a known safety profile.

Editorial conclusions

In the YK-11 versus Ostarine pairing there is no “right” choice for a healthy person. Ostarine has a partly known side-effect profile and modest effectiveness shown in clinical populations; YK-11 has only laboratory data and a completely unknown safety profile.

For athletes, women, young people and those with chronic illnesses or planning children, the editorial team advises abstaining from both substances. For other readers, the rational path is to exhaust the legal tools: training, nutrition, creatine and recovery.

We also recommend reading our materials “YK-11 or Ostarine: what is the difference”, on creatine monohydrate and on how to choose certified sports supplements.

References

1. Dalton JT, Barnette KG, Bohl CE, et al. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle. 2011;2(3):153–161.
2. Kanno Y, Ota R, Someya K, et al. Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression. Biol Pharm Bull. 2013;36(9):1460–1465.
3. Van Wagoner RM, Eichner A, Bhasin S, et al. Chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet. JAMA. 2017;318(20):2004–2010.
4. Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
5. Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr. 2017;14:18.
6. Solomon ZJ, Mirabal JR, Mazur DJ, et al. Selective androgen receptor modulators: current knowledge and clinical applications. Sex Med Rev. 2019;7(1):84–94.
7. World Anti-Doping Agency. The World Anti-Doping Code International Standard: Prohibited List. Montreal: WADA; чинна редакція.