Female athlete triad
Also called: relative energy deficiency in sport, RED-S
What it means
Female athlete triad, now often called RED-S, is a condition where not eating enough to match heavy exercise leads to missed periods and weaker bones.
It can cause real, measurable bone loss at a young age, raising fracture risk decades earlier than typical.
Female athlete triad is a classic name for a pattern seen in some women who exercise a lot while not eating enough to cover the energy cost of their training. It has three connected parts: low energy availability (often alongside disordered eating), loss of regular menstrual periods, and weakened bones. The newer, broader term is RED-S, or relative energy deficiency in sport, because this pattern can affect men too and touches more than bone, including hormones, metabolism, and heart health.
The bone problem happens because chronically under-fueling the body suppresses reproductive hormones, so periods become irregular or stop. This drop in estrogen acts much like an early, abrupt menopause, and bone loss can follow. This is similar to functional hypothalamic amenorrhea, where the body quiets reproductive hormones when it senses too little available energy, and some research on athletes with this pattern has found lower bone density than expected for their age.
Addressing low bone density in this situation is different from typical post-menopausal bone loss, and the underlying approach usually focuses on restoring adequate energy intake and allowing periods to return naturally. Any decision about hormonal treatment, including birth control pills, should be made with a qualified doctor who can weigh the individual situation. Anyone with a history of missed periods from heavy training or disordered eating deserves a bone health check.
Not eating enough to match heavy exercise can stop periods and cause real bone loss at a young age.
Where this leads
WordInadequate nutrition links to low body weight too. Learn how a lower BMI alone is tied to lower bone density and higher fracture risk.
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Related words
Amenorrhea is the absence of menstrual periods, often from low estrogen caused by intense exercise, low body weight,…
Anorexia nervosa is an eating disorder involving severe calorie restriction and low body weight that can seriously…
Premature menopause is when periods stop before about age 45, due to primary ovarian insufficiency, ovary removal,…
Hypogonadism is when the body produces too little estrogen or testosterone, which speeds up bone loss because these…
Low body mass index (BMI) means someone is thinner than average for their height, which is linked to lower bone…
Hormonal birth control can affect bone density depending on the type; the progestin-only injection (Depo-Provera) is…
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
