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CAQ Review

The Female Athlete Triad, Relative Energy Deficiency in Sport, and the Male Athlete Triad: The Exploration of Low-Energy Syndromes in Athletes

Statuta, Siobhan M. MD

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Current Sports Medicine Reports: February 2020 - Volume 19 - Issue 2 - p 43-44
doi: 10.1249/JSR.0000000000000679
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The Female Athlete Triad

The female athlete triad (FAT) is a three-pronged spectrum of interrelated medical conditions among physically active females (1,2). With emerging data, each specific component has morphed into its current definition:

  • low energy availability (EA) with or without disordered eating,
  • menstrual dysfunction,
  • low bone mineral density (BMD).

Identification of one or more of these components is essential, because early intervention can prevent serious adverse health effects. The FAT Cumulative Risk Assessment tool helps quantify risk factors and suggests return-to-play guidelines.

Low EA

A low-calorie state is the center, or etiological factor, of the triad (2–4). This can result from decreased caloric intake, an increase in energy expenditure, or both and can occur unknowingly in athletes ramping up training demands.

  • Daily EA: (energy intake [kcal] − exercise energy expenditure [kcal]) / kg fat-free mass (FFM)
  • Optimal EA: 45 kcal·kg−1 of FFM per day Low EA: <30 kcal·kg−1 of FFM per day
  • A stable body weight can exist despite the body being in a state of low EA
  • Diagnosis: challenging
    • ○ No accurate method exists to collect EA. Dietary logs prove inaccurate
    • ○ Measurable indicators of low EA: reduced resting metabolic rate, low fat mass, low free T3
    • ○ Body mass index (BMI) can be an outward marker of low EA, such as BMI < 17.5 kg/m2 or <85% expected body weight. Age- and sex-adjusted BMI percentiles are recommended through age 20 years
    • ○ Tracking leptin levels may prove useful. Studies are ongoing.

Menstrual Dysfunction

The previously accepted concept that “it is normal for an active female to have irregular menses” is false (2). Varying degrees of dysfunction exist, ranging from subclinical menstrual disturbances (anovulatory cycles) to oligomenorrhea to primary/secondary amenorrhea.

  • Amenorrhea: work-up should rule out endocrinopathies
    • ○ Primary: absence of menarche by age 15 years
    • ○ Secondary: irregular menses for >6 months or the cessation of previously regular menses for 3 months. Evaluation should begin after 3 months of missed periods.
  • Oligomenorrhea: cycle intervals >35 d in adults; >45 d in adolescents
  • Diagnosis: common from history and physical. Consider obtaining the following studies:
    • ○ Luteinizing hormone, follicle stimulating hormone, human chorionic gonadotropin
    • ○ Prolactin
    • ○ Thyroid stimulating hormone, free T4
    • ○ Estradiol, androgen profile
    • ○ Pelvic ultrasound


Bone Z scores (comparisons to comparable aged individuals) are used instead of T scores (2,5,6). Athletes in weight-bearing sports classically have 5% to 15% higher BMD than nonathletes; thus, in this population:

  • Low BMD: Z score < −1.0 warrants further investigation
  • Osteoporosis: Z score ≤ −2.0 with a secondary clinical risk factor for fracture
  • Diagnosis: DEXA scans are used for BMD values. Indications for initial screening or tracking change is determined according to the number of risk factors present and age.
    • ○ Axial and peripheral quantitative computed tomography scanning is being researched as a potential method to provide greater detail regarding bone geometry, mass, and density.

Relative Energy Deficiency in Sport

Relative Energy Deficiency in Sport (RED-S) shares the similar premise that low EA yields deleterious consequences to menstrual function and bone health in women (6), yet the effect is more expansive:

  • Males, disabled athletes, and implications on different races are included. For males, the hypothalamic-pituitary-gonadal hormonal pathway replaces “menstrual function.”
  • Widespread health consequences: immunological, cardiovascular, psychological, endocrine, and so on, in addition to menstruation and bone health
  • Affects performance: increased injury risk, depression, irritability; decreased coordination, muscle strength, concentration
  • Screening tools: the RED-S Clinical Assessment Tool uses a stoplight approach to determining risk states and activity recommendations.

Male Athlete Triad

The male athlete triad is not yet an official entity (7,8). A team of experts is creating a consensus statement to be published in the near future.

  • Evidence indicates male athletes are affected by a low EA state hormonally (e.g., reduced testosterone), but this is difficult to assess.
  • Hypogonadism/low testosterone replaces menstrual dysfunction of the FAT.
  • Diagnosis: evaluate low BMD or multiple bony stress injuries
  • Screening: ensure a level of suspicion
    • ○ Modified female screening tools have been used but are less sensitive.

Each of these conditions centers on a basis of low EA among active individuals. Treatment must address reversing this energy deficit, in addition to any other findings. A multidisciplinary team approach, including a team physician, a sports dietician, and mental health practitioner, is advisable for care.


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8. Tenforde A, Barrack MT, Nattiv A, et al. Parallels with the female athlete triad in male athletes. Sports Med. 2016; 46:171–82.
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