Human and dietary nutrition is not an exact science by any means, this can be seen practically daily in consultations and when working with athletes.
Many athletes restrict their intake and develop low energy availability because they fear that eating more will immediately increase body fat and reduce performance. In reality, intake must be closely aligned with physiological needs and the energy expended during training/competition.
It's a shame that when we talk about human physiology 1+1≠2 and when an athlete is in a state of energy deprivation or simply does not provide as much as they expend, the human body is not stupid and becomes much more efficient, turning off functions and putting some of them in 'power-saving mode.' Think about your mobile phone
What happens to it when it has 5% battery left? Surely all functions will worsen and will not be as smooth.
The same thing happens to an athlete; in this way, when we provide the appropriate nutrients and energy to our athlete, even if the intake may be higher, by improving their rest and recovery, their vital functions, increasing their training volume, reducing fatigue during it, and decreasing the risk of injury and illness, all this indirectly increases their energy expenditure dynamically, making an apparent 'caloric surplus' equivalent to maintenance energy or even an adjusted deficit. A typical case where you increase calories and improve body composition.
Regarding the possible consequences both in terms of health and performance of a low energy availability;
To avoid going too deeply into the physiology and pathophysiology of the different organs, we will briefly mention the systems that have been found to be affected in the various studies (most of them being interrelated with each other).
Where due to this relative energy deficiency, we may be causing problems both at the neuroendocrine level including the disruption of the hypothalamic-pituitary-gonadal axis, alterations in thyroid function, changes in appetite-regulating hormones (e.g., decreased leptin and oxytocin, increased ghrelin, peptide YY, and adiponectin), decreased insulin and insulin-like growth factor (IGF-1), increased resistance to growth hormone (GH), and elevated cortisol. Many of these hormonal changes are likely to occur to conserve energy for more important bodily functions or to use the body's energy reserves for vital processes.All of this indirectly affecting both metabolism and the growth and development of the individual, menstrual function (amenorrhea), gastrointestinal system, immune system (increasing the risk of contracting diseases, especially in the upper respiratory tract), hematological level (in iron metabolism), psychological level (finding a bidirectional arrow, as it is not known whether the alterations in terms of eating disorders occur as a cause or consequence of this), worsening the lipid profile and increasing cardiovascular risk due to an increase in LDL-C, inflammation factors, and endothelial damage; in turn, we also find secondary effects at the level of bone metabolism, increasing the risk of osteopenia, osteoporosis, and fractures at an early age.
In performance, we find more of the same, since inadequate energy availability will produce different behaviors or undesirable effects when training or competing: irritability, depression, decreased glycogen levels, decreased strength, decreased cardiovascular endurance, increased risk of injury, decreased adaptations, as well as response in training, as well as decreased coordination and cognitive function in decision-making.
The treatment is generally based on increased energy intake, but it may also require changes in the choices of these, the distribution of energy, and other characteristics of the diet; these changes must be individualized and periodized according to energy expenditure and the athlete's exercise goals. A reduction or cessation of exercise may be necessary, depending on the severity of the energy deficit, symptoms, and level of compliance.
References
- De Souza, M. J., Koltun, K. J., & Williams, N. I. (2019). The role of energy availability in reproductive function in the female athlete triad and extension of its effects to men: an initial working model of a similar syndrome in male athletes. Sports Medicine, 1-13.
- Mountjoy M, Sundgot-Borgen JK, Burke LM, Ackerman KE, Blauwet C, Constantini N, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. Br J Sport Med. 2018;52(10):687–97.
- Keay N, Rankin A. Infographic. Relative energy deficiency in sport : an infographic guide. 2019;0(0):1–3.
- Keay N, Francis G, Hind K. Low energy availability assessed by a sport-specific questionnaire and clinical interview indicative of bone health, endocrine profile and cycling performance in competitive male cyclists. 2018;1–7.
- Melin AK, Heikura IA, Tenforde A, Mountjoy M. Energy Availability in Athletics : Health, Performance, and Physique. 2019;152–64.
- Keay N, Francis G. Infographic. Energy availability: concept, control and consequences in relative energy deficiency in sport (RED-S). Br J Sports Med. 2019;0(0):bjsports-2019-1
