The past three decades have seen an evolution in our understanding of problems involved with energy deficiency in athletes. The first defining step involved the formalisation of the Female Athlete Triad syndrome by the American College of Sports Medicine in 1997 (see Figure 6.1A), with advocacy for the recognition of a common presentation and interrelationship of eating disorders, amenorrhoea and osteoporosis/bone injuries in female athletes (Otis et al. 1997). The formation of the Female Athlete Triad Coalition and further refining of the American College of Sports Medicine model in 2007 (Nattiv et al. 2007) focused awareness that each corner of the Triad involves a spectrum between health and a disease (see Figure 6.1B). Furthermore, each athlete can ‘travel’ along each continuum at different times and rates, and there is a need for concern about any movement towards ill-health, rather than waiting for a clinical diagnosis to be reached. Additional insights included an expansion of the dietary contribution to the Triad, with recognition that energy deficiency rather than an eating disorder per se creates hormonal and metabolic perturbations and can be caused by a range of scenarios. It has been more clearly articulated that the particular type of energy deficiency in the Triad is low energy availability (LEA); the particular type of reproductive disorder is functional hypothalamic menstrual disorders (hereafter known as menstrual disorder/disturbance); and the particular type of skeletal impairment is the uncoupling of bone turnover, with an increased rate of bone resorption and a reduced rate of bone formation (Loucks 2015).
An expanded model was developed by an International Olympic Committee task force (Mountjoy et al. 2014, 2018) to incorporate the association of LEA and additional health concerns and to include male athletes within the definition of populations at risk (see Figure 6.1C). Although these concepts were considered contentious by the Female Athlete Triad Coalition (de Souza et al. 2014a), the Triad model was reissued in 2018 to include males (de Souza et al. 2019) (see Figure 6.1D). While differences or different perspectives continue to exist between the current models of the Triad and relative energy deficiency in sport (RED-S), the common element is that a range of impairments to the health and performance of athletes can be attributed to, or at least associated with, exposure to LEA. Proponents of each of these models have provided comprehensive overviews of the mechanisms by which LEA can create perturbations to hormones, metabolism and body functions (Mountjoy et al. 2018; de Souza et al. 2019). A more recent perspective (Areta et al. 2021) summarises the history and current understanding of LEA in sport, while identifying some of the issues that remain unresolved.
Overview of the evolution of models related to energy deficiency in athletes