MK-2866 (Ostarine) is used by mouth to improve athletic performance and for involuntary weight loss in people who are very ill, also known as cachexia or wasting syndrome. But there is very little good scientific research to support these uses.
Ostarine attaches to proteins in the body known as androgen receptors. When ostarine binds to these receptors, it tells the muscles in the body to grow. Unlike some other chemicals that bind to androgen receptors, such as steroids, ostarine doesn’t seem to cause as many side effects in other parts of the body.