Ostarine, also known as MK-2866 or Enobosarm, is a selective androgen receptor modulator (SARM) that has gained popularity in bodybuilding communities for its purported ability to increase muscle mass and strength. The scientific basis for its use stems from several clinical studies, primarily in populations with muscle-wasting conditions such as cancer cachexia, sarcopenia, and other catabolic states. In these contexts, Ostarine has demonstrated the ability to increase lean body mass and improve physical function compared to placebo, with fewer androgenic side effects than traditional anabolic steroids.

In healthy individuals or athletes, the data are less robust, as Ostarine is not approved for use by any regulatory agency for bodybuilding or athletic performance, and most studies have not focused on these groups. Nevertheless, its mechanism—selectively binding to androgen receptors in muscle and bone—provides a plausible rationale for its anabolic effects. This has led to off-label and non-medical use among bodybuilders seeking muscle growth and fat loss. Importantly, Ostarine is on the World Anti-Doping Agency (WADA) list of prohibited substances due to concerns about performance enhancement and potential health risks, including hormone suppression, liver toxicity, and unknown long-term effects.

In summary, there is moderate scientific evidence (rating: 3) supporting Ostarine's anabolic effects in clinical settings involving muscle-wasting, with only indirect or anecdotal support in bodybuilding. Its safety and efficacy for healthy individuals remain unproven.