Energy Availability: Concept, Control and Consequences in relative energy deficiency in sport (RED-S)

Relative energy deficiency in sport (RED-S) is an issue of increasing concern in sports and exercise medicine. RED-S impact exercisers of all levels and ages, particularly where low body weight confers a performance or aesthetic advantage. Key to mitigating adverse health and performance consequences of RED-S is supporting athletes and dancers to change behaviours. These infographics aim to assist clinicians in communicating the concepts to exercisers and in implementing effective management of athletes in their care[1].


Figure 1 illustrates the concept of energy availability (EA) in RED-S. Preferentially energy derived from dietary intake covers the demands of training and the remaining energy, EA, is, quantified in Kcal/Kg of fat free mass[2]. In Figure 1, the central bar illustrates adequate EA in an athlete where energy intake is sufficient to cover the demands of training and fundamental life processes to maintain health. Conversely, low energy availability (LEA) is a situation of insufficient EA to cover basic physiological demands. LEA leads to the adverse consequences of RED-S[3]. LEA can arise unintentionally or intentionally, due to a mismatch between energy intake and energy requirement. In Figure 1 the bar on the left shows LEA resulting from reduced energy intake with maintained training load. On the right, LEA is a consequence of increased training load with maintained energy intake.

Figure 2 illustrates that EA is under the control of an athlete[4]. The three behaviours relating to training, nutrition and recovery determine EA. Integrated periodisation of these behaviours results in optimal health and performance. Conversely, an imbalance in these behaviours results in suboptimal functionally. LEA in the case of high training loads relative to nutritional intake. Thus, this figure reinforces the important point in the IOC statements on RED-S that psychological factors which determine these behaviours are key in both the development, continuation and management of RED-S[2,3].


Figure 2 also shows the temporal, synergistic effect of these behaviours to ensure a fully functioning endocrine system. Hormones are key for health and to drive positive adaptations to exercise, to improve athletic performance. Thus hormones can be informative in tracking the response of an individual to these three input variables. Furthermore, endocrine markers relate to the RED-S clinical outcome of stress fracture in athletes, being more reliable as objective, quantifiable indicators of EA than numerical calculation of EA from direct assessment[5].


Nicola Keay1, Gavin Francis2

1 Department of Sport and Exercise Sciences, Durham University

2 Science4Perforamnce, London

Br J Sports Med 2019;0:1–2. doi:10.1136/bjsports-2019-100611


1 (accessed 21/01/2019) Health4Performance Educational BASEM website raising awareness of RED-S Working group on RED-S British Association of Sport and Exercise Medicine 2018

2 Mountjoy M, Sundgot-Borgen J, Burke L et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update Br J Sports Med2018;52(11):687-697

3 Mountjoy M, Sundgot-Borgen J, Burke L et al. The IOC consensus statement: beyond the Female Athlete Triad–Relative Energy Deficiency in Sport (RED-S). Br J Sports Med2014;48(7):491-7

4 Burke L, Lundy B, Fahrenholtz L et al, & Melin. Pitfalls of conducting and interpreting estimates of energy availability in free-living athletes. International Journal of Sport Nutrition and Exercise Metabolism2018; 28(4):350–363.

5 2Heikura I, Uusitalo A, Stellingwerff T et al. Low energy availability is difficult to assess but outcomes have large impact on bone injury rates in elite distance athletes. International Journal of Sport Nutrition and Exercise Metabolism2018; 28(4):403–411.

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