AIS Sports Nutrition

Female Athlete Triad

The Female Athlete Triad (Triad) is described by the American College of Sports Medicine (2007) as the interrelationship between energy availability, menstrual function and bone mineral density. This interrelationship ranges from health to disease, and with appropriate nutrition the three components promote robust health in female athletes. On the other end of the spectrum, clinical manifestations of the Triad include eating disorders, functional hypothalamic amenorrhoea and osteoporosis. Individually, or in combination, these three conditions can impact significantly on the health of a female athlete. 

The spectrums for the three components of the Triad are as follows:

  • energy availability ranges from optimal energy availability to low energy availability (with or without an eating disorder)
  • bone mineral density ranges from optimal bone health to osteoporosis
  • menstrual function ranges from eumenorrhea to amenorrhea

A female athlete may move along the three spectrums at different rates, in different directions according to her diet and exercise habits (see Figure 1 below). The sensitivity of the three spectrums varies because energy availability can change in a day, an effect on menstrual status may not become evident for a month or more, and the impact on bone mineral density may not be detectable for a year. 

Figure 1 – Female athlete triad (ACSM position stand, 2007)

Figure 1 – Female athlete triad (ACSM position stand, 2007)

Energy Availability

Low energy availability is the key component of the Triad and appears to be the factor that negatively affects reproductive and skeletal health. Energy availability is defined as dietary energy intake minus exercise energy expenditure, and is the amount of dietary energy remaining for other body functions (outside of exercise). Low energy availability appears to occur below an energy availability of 30 kcal/kg of fat free mass per day (126 kJ/kg of fat free mass). When energy availability is too low, physiological functions in the body are impaired to reduce the amount of energy being used. These functions can include cellular maintenance, growth, reproduction and body temperature regulation.
It is important to recognise that low energy availability in a female athlete may be due to a number of reasons: inadvertent, intentional or psychopathological.  Not all cases of low energy availability are a result of an eating disorder and the cause should be identified before treatment commences. Disordered eating, and more serious eating disorders, pose significant risk to a female athlete’s health. Early identification and treatment is paramount to a positive outcome, as is a multi-disciplinary team approach to treatment.

Menstrual Function

Eumenorrhea is defined as normal menstrual function whereas amenorrhea is the absence of menstrual cycles for more than three months.  Primary amenorrhea refers to a delay in the age of menarche (first menstrual cycle) whereas secondary amenorrhea is the absence of menstrual cycles lasting longer than three months. 

Low energy availability and the affect on menstrual function:

  • Severe dietary restriction alone can disrupt reproductive function however, the more physically active a female is, the less dietary restriction required to cause low energy availability
  • The physical ‘stress’ of exercise is not the cause of the disruption to menstrual function, low energy availability is.  It should be noted that for some individuals, a decrease in energy expenditure from exercise is required to help restore energy balance.  However, for most, an increase in dietary energy intake to better meet the energy demands of exercise is sufficient to restore menstrual function.

Bone Mineral Density (BMD)

Osteoporosis is a potentially serious condition where compromised bone strength may predispose someone to an increased risk of fractures.  A low BMD is used to diagnose osteoporosis.  It should be noted that female athletes participating in weight bearing sports usually have a BMD 5-15% higher than non-athletes.  This is an important point to consider when interpreting an individual’s BMD results.  

Adequate energy availability and the affect on bone health:

  • Promotes bone health directly by stimulating the production of hormones that promote bone formation
  • Promotes bone health indirectly by preserving eumenorrhea and oestrogen production that stems bone resorption

Men

Cases of the Triad are much less common in male athletes, mainly due to the difficulty in detecting reproductive effects in men compared to women.  The prevalence is thought to be much lower in male athletes than female athletes, mainly because fewer male athletes engage in diet and exercise regimes that severely reduce energy availability.  Metabolic and reproductive hormones can be impaired in male athletes with low energy availability and these hormone levels have been restored to normal with increased feeding within a week whilst training continues.  Further research into the Triad in male athletes would be beneficial to better understand the prevalence, how to identify athletes at risk and the ideal treatment.

Conclusion

Female athletes should be monitored for signs of the Triad, with early identification and intervention important for positive health outcomes for the athlete.  A female athlete who presents with one of the clinical manifestations of the Triad should be assessed for the other two by an appropriate health professional.
The first step in treatment of the Triad is increasing energy availability, whether this is via an increase in energy intake, a decrease in exercise energy expenditure or a combination of the two.  By increasing energy availability, the aim is to restore menstrual cycling and increase in BMD.  Menstrual function may be restored by increasing energy availability to more than 30 kcal/kg of fat free mass.  An increase in BMD is strongly associated with an increase in body weight and therefore weight gain may be required.   
Overall, the benefits of exercise to a female’s health far outweigh the risk of the negative health consequences associated with the Triad.

Further reading

  • Nattiv, A., A.B. Loucks, M.M. Manore, C.F. Sanborn, J. Sundgot-Borgen, and M.P. Warren. American College of Sports Medicine Position Stand: The female athlete triad. Med. Sci. Sports Exerc. 2007. 
  • Loucks, A.B., M. Verdun, and E.M. Heath. Low energy availability, not stress of exercise, alters LH pulsatility in exercising women. J. Appl. Physiol. 84:37-46, 1998.
  • Manore, M,M., L. Ciadella Kam, and A.B. Loucks. The female athlete triad: Components, nutrition issues, and health consequences. J. Sports. Sci. 25(S1): S61-S71, 2007.
  • Williams, N.I., A.L. Caston-Balderrama, D.L. Helmreich, D.B. Parfitt, C. Nosbisch, and J.L. Cameron. Longitudinal changes in reproductive hormones and menstrual cyclicity in cynomolgus monkeys during strenuous exercise training: abrupt transition to exercise-induced amenorrhoea. Endocrinology. 142: 2381-9, 2001a.
  • Williams, N.I., D.L. Helmreich, D.B. Parfitt, A.L. Caston-Balderrama, and J.L. Cameron. Evidence for a causal role of low energy availability in the induction of menstrual cycle disturbances during strenuous exercise training. J. Clin. Endrocrinol. Metab. 86:5184-93, 2001b.

Written by AIS Sports Nutrition, last updated December 2010. © Australian Sports Commission.

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