Paeds · rheumatology-musculoskeletal-and-sports
Relative energy deficiency in sport and athlete nutrition
Also known as RED-S · relative energy deficiency in sport · female athlete triad · low energy availability · athlete under-fuelling · energy availability · functional hypothalamic amenorrhoea · athlete triad · bone stress injury in the athlete · delayed menarche in the athlete
A fellowship approach to relative energy deficiency in sport and athlete nutrition: low energy availability is the central driver that, when energy intake falls short of the energy spent in training, suppresses the hypothalamic-pituitary axis and dismantles reproductive function, bone accrual, and a dozen other systems in the growing athlete — anchored by the Female Athlete Triad screen of energy intake, menstrual function, and bone health, the energy-availability threshold of approximately thirty kilocalories per kilogram of fat-free mass per day, and the multidisciplinary, energy-restoration-first pathway that protects the adolescent from the stress fracture, the lost menstrual cycles, and the lifelong bone deficit.
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Red flags
- An adolescent athlete with a stress fracture in a weight-bearing bone, especially a recurrent or high-risk site such as the femoral neck, sacrum, or pelvis, has low energy availability and disordered bone metabolism until assessed and treated
- A menstrual cycle that is absent for three or more months, or a primary amenorrhoea with no menarche by fifteen years in an athlete, is functional hypothalamic amenorrhoea from energy deficiency until evaluated and never dismissed as normal for a sportswoman
- A falling weight or a body mass index falling across centiles in a training adolescent, or a drive for thinness that dominates the young athlete's life, signals an eating disorder that carries the highest Triad and RED-S risk and is a restriction-from-play indication
- Bradycardia, orthostatic hypotension, lanugo, or hypothermia in a lean athlete is the physiological signature of an advanced energy deficit and demands urgent multidisciplinary assessment for an eating disorder
- Delayed puberty or a slowing of growth and maturation in a child athlete, with a bone age that lags the chronological age, is energy deficiency interfering with growth until the energy balance is corrected
- Iron-deficiency anaemia, recurrent infections, slow recovery, or persistent fatigue in a training adolescent may be the multi-system presentation of low energy availability and warrants the full athlete assessment
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Care settings
Clinical exam formats
Board mappings
- Adolescent medicine - assess the training adolescent for low energy availability, menstrual function, and bone health
- Growth and Development - delayed puberty and the slowing of growth in the over-trained child
- Health promotion - nutrition, the pre-participation screen, and the safety-net for the young athlete
- Sports and exercise medicine - apply the Female Athlete Triad and RED-S frameworks and the energy-availability threshold
- Endocrinology - functional hypothalamic amenorrhoea and the hypothalamic-pituitary suppression of energy deficiency
- Renewed curriculum for first-year trainees from 2027 - Learning goal 6: Clinical management - essential general paediatrics
- Adolescent medicine 10-12
- Growth and puberty 10-12
- Clinical Applications
- Long Cases
- Short Cases
- 8. Growth and puberty - delayed puberty and the effect of energy balance on growth and menarche
- 10. Promotion of mental health and wellbeing - disordered eating and the drive for thinness in the young athlete
- 4. Professional skills and knowledge: Patient management - the multidisciplinary pathway
- Foundation of Practice (FOP)
- Theory and Science (TAS)
- Applied Knowledge in Practice (AKP)
- Clinical
- History
- Communication
- Video
- General Pediatrics Content Outline - Adolescent medicine and the reproductive examination
- General Pediatrics Content Outline - Nutrition and the under-fuelled athlete
- General Pediatrics Content Outline - Universal Task 5: Patient Management
- Patient Care 4: Clinical Reasoning
- Patient Care 5: Patient Management
- Medical Knowledge 2: Conditions common in pediatric primary care
- Systems-Based Practice 2: Coordinated acute and chronic care
- Medical Expert
- Pediatrics: Foundations EPA #5 - Performing a focused physical examination
- Pediatrics: Adolescent health and sports medicine applied domain
A fourteen-year-old cross-country runner presents with three months of shin pain and no menstrual period since she increased her training — a bone stress injury on the background of low energy availability and secondary amenorrhoea, the classic Triad presentation. A sixteen-year-old dancer who restricts her intake to stay lean has a sacral stress fracture and a body mass index that has fallen across the centiles — relative energy deficiency in sport at its most destructive, with an eating disorder driving the deficit. A fifteen-year-old swimmer has never had a period, and her bone age lags her chronological age — delayed puberty and slowed growth from the chronic energy deficit of the growing athlete. The task in each is to find the energy deficit, quantify the risk, and restore the energy before the bone breaks and before the window for bone accrual closes. [4] [9]
Run the athlete assessment in five moves. Screen every athlete at the pre-participation visit, because the deficit is silent until the cycle stops or the bone breaks. Cycle asks the menstrual history, because the absent or irregular period is the most reliable clinical marker of energy deficiency. Bone looks for the stress fracture and the low density, because the skeleton is system deficit dismantles first and most permanently. Fuel quantifies the energy availability and restores it, because energy restoration is the only treatment that reverses the syndrome. Refer to the multidisciplinary team, because the dietitian and the psychologist are as load-bearing as the physician. [2] [4]
Overview & Definition
Relative energy deficiency in sport is the syndrome that arises when the energy an athlete expends in training chronically exceeds the energy consumed in the diet, and the body, unable to sustain every system on the deficit, down-regulates the functions it can defer. The central and measurable quantity is energy availability, defined as the dietary energy intake minus the exercise energy expenditure, divided by the fat-free mass, and expressed as kilocalories per kilogram of fat-free mass per day. Energy availability is the single number that ties the diet to the sport to the physiology, and the fellowship candidate can say the definition aloud and explain why the fat-free mass is the denominator rather than the total body weight. [5] [1]
The threshold that the candidate must hold is the level of energy availability at which the reproductive axis is disrupted. The seminal experiment of Loucks and Thuma established that luteinising hormone pulsatility, the brain's signal to the ovary, is measurably disrupted when energy availability falls below approximately thirty kilocalories per kilogram of fat-free mass per day in regularly menstruating women, and that optimal function is sustained at approximately forty-five kilocalories per kilogram of fat-free mass per day and above. The thirty-kilocalorie threshold is number examiner probes, and the forty-five-kilocalorie optimal is its complement. [5] [2]
The clinical importance flows from the fact that the growing athlete is building her bone bank in parallel with her sport, and the energy deficit dismantles the bone accrual at the exact developmental window when it matters most. An adolescent accrues the great majority of her adult skeletal mass between the early teens and the early twenties, and the bone she fails to lay down during these years is never fully recovered. A stress fracture in a cross-country runner is the visible tip of the deficit, and the lifelong deficit in bone mineral density is the invisible mass of the iceberg beneath it. The fellowship task is to find the deficit, quantify the risk, and restore the energy while the bone window is still open. [9] [10]
References11ShowHide
- [1]Mountjoy M, Sundgot-Borgen J, Burke L, Carter S, Constantini N, Lebrun C, et al. The IOC consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S). Br J Sports Med, 2014.PMID 24620037
- [2]Mountjoy M, Sundgot-Borgen JK, Burke LM, Ackerman KE, Blauwet C, Constantini N, et al. International Olympic Committee (IOC) Consensus Statement on Relative Energy Deficiency in Sport (RED-S): 2018 Update. Int J Sport Nutr Exerc Metab, 2018.PMID 29771168
- [3]Mountjoy M, Ackerman KE, Bailey DM, Burke LM, Constantini N, Hackney AC, et al. 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med, 2023.PMID 37752011
- [4]De Souza MJ, Nattiv A, Joy E, Misra M, Williams NI, Mallinson RJ, et al. 2014 Female Athlete Triad Coalition Consensus Statement on Treatment and Return to Play of the Female Athlete Triad. Curr Sports Med Rep, 2014.PMID 25014387
- [5]Loucks AB, Thuma JR. Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. J Clin Endocrinol Metab, 2003.PMID 12519869
- [6]Gordon CM, Ackerman KE, Berga SL, Kaplan JR, Mastorakos G, Misra M, et al. Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, 2017.PMID 28368518
- [7]Fahrenholtz IL, Melin AK, Wasserfurth P, et al. Risk of Low Energy Availability, Disordered Eating, Exercise Addiction, and Food Intolerances in Female Endurance Athletes. Front Sports Act Living, 2022.PMID 35592590
- [8]Barrack MT, Domino S, Gray VB, et al. Support for inadvertent undereating in female adolescent athletes with clinical indicators of low energy availability. J Sci Med Sport, 2023.PMID 37248163
- [9]Tenforde AS, DeLuca S, Wu AC, et al. Prevalence and factors associated with bone stress injury in middle school runners. PM R, 2022.PMID 34251763
- [10]Tenforde AS, Kraus E, Fredericson M. Bone Stress Injuries in Runners. Phys Med Rehabil Clin N Am, 2016.PMID 26616181
- [11]Holtzman B, Tenforde AS, Parziale AL, et al. Characterization of Risk Quantification Differences Using Female Athlete Triad Cumulative Risk Assessment and Relative Energy Deficiency in Sport Clinical Assessment Tool. Int J Sport Nutr Exerc Metab, 2019.PMID 31034246