The Female Athlete Triad Explained: Energy, Periods and Bone

What is the female athlete triad?

The female athlete triad is the interrelationship between three conditions in active girls and women: low energy availability, menstrual dysfunction, and low bone mineral density. In the clinical literature it is defined as "low energy (with or without an eating disorder) in combination with a menstrual disorder and altered mineral bone density" StatPearls Publishing / NCBI Bookshelf, 2023.

The three components are linked, and each sits on a spectrum rather than being simply present or absent:

• Low energy availability — the dietary energy left over after exercise is too low to support normal physiological function. This can arise from disordered eating, or from inadvertent under-fuelling with no eating disorder at all Case Reports in Women's Health (Zavatta & Clarke), via PubMed Central, 2020.
• Menstrual dysfunction — most often oligomenorrhoea (infrequent periods) or amenorrhoea (absent periods), driven by functional hypothalamic suppression with low oestrogen Case Reports in Women's Health, via PubMed Central, 2020.
• Low bone mineral density — reduced bone strength that raises fracture risk StatPearls Publishing / NCBI Bookshelf, 2023.

How does the female athlete triad develop?

It starts with an energy shortfall: when an athlete consistently burns more than she eats, the body downregulates its reproductive and skeletal systems to conserve energy. Chronic low energy availability suppresses hypothalamic function, which reduces oestrogen production. Because oestrogen normally restrains bone breakdown, low oestrogen tilts bone turnover toward loss — so the same energy deficit that stops periods also weakens bone StatPearls Publishing / NCBI Bookshelf, 2023.

That is why the three components travel together. Missed or irregular periods are not just a nuisance of hard training — in this setting they are a visible signal that the hormonal environment bone depends on has been disrupted. The NHS lists "doing too much exercise" and "sudden weight loss" among the common causes of stopped or missed periods, which is exactly the pattern seen in the triad NHS, 2024.

Who is at risk of the female athlete triad?

Risk is highest in sports that combine high energy demands with pressure to stay lean. Females in "endurance sports such as track and field, swimming, and rowing, or those requiring subjective judging like gymnastics and figure skating are most at risk" StatPearls Publishing / NCBI Bookshelf, 2023. Ballet dancers and long-distance runners are classic examples.

Disordered eating is a major driver in some athletes but not all. Female athletes are 5 to 10 times more likely than male athletes to have an eating disorder, and clinical eating disorders affect an estimated 16% to 47% of elite female athletes StatPearls Publishing / NCBI Bookshelf, 2023. Adolescents and young women are a particular concern, because this is the window when peak bone mass is being built — and lost ground here can be hard to recover.

What are the consequences — stress fractures and lasting low bone density?

The most common bone consequence is a stress fracture, and the most serious long-term one is bone density that may not fully recover. In female athletes, low bone mineral density typically shows up first as a bone stress reaction or stress fracture, commonly in the lower limbs Case Reports in Women's Health, via PubMed Central, 2020.

Here is a counter-intuitive point worth holding onto: active people would normally be expected to have stronger bones than non-athletes — around 5% to 15% higher bone mineral density than age-matched non-athletes StatPearls Publishing / NCBI Bookshelf, 2023. So a bone-density reading that merely looks "average" for a young woman who trains hard can itself be a warning sign, not reassurance.

How does the triad relate to RED-S?

The female athlete triad now sits within the broader concept of RED-S — Relative Energy Deficiency in Sport. In its Relative Energy Deficiency in Sport (RED-S) consensus statements, updated in 2018 and 2023, the International Olympic Committee recognised that low energy availability harms many body systems beyond periods and bones — and that it affects male and para athletes too, not only women Wu Tsai Human Performance Alliance summarising British Journal of Sports Medicine 2023;57:1073-1097, 2023.

The triad has not been discarded — it remains a well-recognised framework for the specific energy–menstrual–bone axis in women, and it is often the most practical lens for a female athlete presenting with irregular periods and a stress fracture. RED-S is the wider umbrella that captures the same energy shortfall across both sexes and across systems such as immunity, metabolism and cardiovascular health. If you want the full picture of the broader model, see our companion guide to RED-S syndrome and bone health.

How is the female athlete triad recognised and managed?

The priority is not to treat the bone loss in isolation — it is to restore energy availability, delivered by a multidisciplinary team. First-line treatment corrects the underlying cause through increased nutritional intake, reduced training load, or both, with medication considered depending on the severity of the case StatPearls Publishing / NCBI Bookshelf, 2023. Because disordered eating is often involved, an interprofessional team — typically a sports physician, a sports dietitian and a mental-health professional — is central to recovery, with hormonal treatment considered as a secondary step for menstrual dysfunction StatPearls Publishing / NCBI Bookshelf, 2023. Careful nutritional management is consistently framed as the foundation of care in the triad and RED-S Nutrients (MDPI), via PubMed Central, 2024.

Loading exercise still matters for the skeleton — the Royal Osteoporosis Society advises combining weight-bearing impact with muscle-strengthening work to build and maintain bone strength Royal Osteoporosis Society, 2024, and our guide to the best exercises for bone health covers how. But in the triad, no amount of training can substitute for eating enough; adding load to an under-fuelled skeleton addresses the wrong side of the equation.

Tracking bone density over time is part of good management, and because monitoring means repeat assessment, a radiation-free option is attractive. Our bone health assessment uses REMS technology — an ultrasound-based, radiation-free method — which makes reassessing across a season easier to justify than repeated X-ray-based DXA. (Note: the triad research above evaluates DXA specifically; REMS is offered here as SMB's own modality, not something these particular papers assessed.)

If you are an athlete, coach or parent who recognises these signs — irregular or absent periods, recurrent stress fractures, persistent under-fuelling — a baseline bone assessment gives you a number to track against as nutrition and training are corrected. You can book a radiation-free bone health assessment to establish that baseline.

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This article is part of our athletes and active people series.