Article
Low Energy Availability Score Overview
Benjamin T. House, Andy J. Galpin, Dan Garner, Vince Kreipke, and Thomas R. Wood

What Is the Low Energy Availability?

Problematic Low Energy Availability (LEA) and/or Relative Energy Deficiency in Sport (RED-S) results when an athlete does not have enough calories to support and maintain normal physiologic functions [1-3]. Being in a LEA state for too long can cause health and performance to decline [2].

LEA can occur due to insufficient energy intake through diet (i.e., too few calories) and/or excessive energy expenditure from exercise (i.e., burning too many calories), and can occur in the absence of negative energy balance or a caloric deficit. An athlete can be in energy balance and still in a state of low energy availability if they are maintaining a body fat level that requires excessively low caloric intake and/or high energy expenditure [4].

Energy availability is expressed as kcal/kg FFM/day, and is defined in the scientific literature in the form of a mathematical formula: EA [Energy Availability] = EI [Dietary energy Intake (kcal)] - EEE [Exercise Energy Expenditure (kcal)] / FFM [Fat-­Free Mass (kg) / day]

The risk categories for LEA based on energy availability are as follows: high risk (≤ 30 kcal/kg FFM), moderate risk (30–45 kcal/kg FFM), and no risk (≥ 45 kcal/kg FFM)[1-3, 5, 6]. The prevalence of RED-S in athletes has been reported to be upwards of 45% or more, though additional research is needed [6, 7]. The body fat percentage and energy availability risk thresholds at which females start to see physiologic and hormonal/menstrual cycle disruptions are highly variable (i.e., some females may see disruptions at 25% body fat or greater, and some may not see negative effects until body fat percentages in the high teens) [8-10]. The energy availability threshold where negative impacts from LEA occur is likely significantly lower in males on average (i.e., perhaps ≤ 25 kcal/kg FFM) [11-14]. However, some males may see deleterious effects from LEA at body fat percentages in the mid-teens, and some may not show signs or symptoms even in single-digit body fat percentages [10, 11, 15].

Keywords: Low Energy Availability, Relative Energy Deficiency in Sport, Performance

Associated Biomarkers

Female Biomarkers Male Biomarkers
Triglycerides Triglycerides
Total Testosterone Total Testosterone
IGF-1 IGF-1
C-Peptide C-Peptide
HbA1c HbA1c
WBC SHBG
Leptin WBC
Total T3 Leptin
Free T3 Total T3
HDL Free T3

Experienced Physiological Effects:

  • Increased Fatigue/Low Energy
  • Low Mood/Increased Irritability
  • Decreased Sex Drive
  • GI Symptoms

Physiology Deep Dive:

A plethora of systems can be negatively affected due to a prolonged LEA state. Hormonally, LEA can result in lowered leptin [12, 16-24], reduced IGF-1 [10, 18, 20, 21, 25-31], decreased total + free testosterone and increased sex-hormone binding globulin [10, 13-15, 21, 29, 31-35], and reduced thyroid hormones [14, 20, 21, 23, 27, 28, 31-33, 36, 37]. The immune, hematopoietic (blood cell production), and iron storage systems can also be negatively affected by LEA, with lowered white blood cells, neutrophil to lymphocyte ratio, hemoglobin, hematocrit, and ferritin [13, 14, 25, 35, 38, 39]. Lowered bone mineral density and increased risk of stress fracture are also possible with long-term LEA [20, 28, 30, 40-44]. Metabolically, lowered insulin, triglycerides, and c-peptide are indicative of insufficient energy availability [12, 15, 20, 30, 33, 36, 45, 46]. LEA states are also associated with decreases in sport availability (i.e., missed practices & games), recovery, adaptations to training, endurance, strength, power, and even motivation [2].

Constraint Zones:

Green:

A green score means that the athlete is unlikely to be in a state of problematic LEA. Depending on the goals of the athlete, an energy deficit, maintenance, or surplus strategy could be utilized.

Yellow:

Problematic LEA is potentially occurring. The athlete should carefully measure their energy availability and complete the LEAF-Q or LEAM-Q. Performance should be monitored and, depending on the circumstances as well as the near and long-term goals of the athlete, an increase in kcals and/or a decrease in energy expenditure may be warranted. An increase in carbohydrate availability may also be considered.

Orange:

Problematic LEA is likely. The individual should carefully measure their energy availability and complete the LEAF-Q or LEAM-Q. Performance should be monitored and, depending on the circumstances as well as the near and long-term goals of the athlete, an increase in kcals and/or a decrease in energy expenditure may be warranted. An increase in carbohydrate availability may also be considered.

Red:

Problematic LEA is evident. The athlete should carefully measure their energy availability and complete the LEAF-Q or LEAM-Q. An increase in kcals and/or a decrease in energy expenditure is likely appropriate. Body fat may need to be gained to allow for sufficient/optimal long-term energy availability [4, 8]. Consulting an experienced registered dietitian or medical provider may be warranted.

References

  1. Wasserfurth, P., et al., Reasons for and Consequences of Low Energy Availability in Female and Male Athletes: Social Environment, Adaptations, and Prevention. Sports Med Open, 2020. 6(1): p. 44.
  2. Mountjoy, M., et al., 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med, 2023. 57(17): p. 1073–1097.
  3. Burke, L.M., et al., Mapping the complexities of Relative Energy Deficiency in Sport (REDs): development of a physiological model by a subgroup of the International Olympic Committee (IOC) Consensus on REDs. Br J Sports Med, 2023. 57(17): p. 1098–1108.
  4. Helms, E., Can You Stay Shredded? MASS, 2022. 6(7).
  5. Stellingwerff, T., et al., Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities. Sports Med, 2021. 51(11): p. 2251–2280.
  6. Gallant, T.L., et al., Low Energy Availability and Relative Energy Deficiency in Sport: A Systematic Review and Meta-analysis. Sports Med, 2025. 55(2): p. 325–339.
  7. Jeukendrup, A.E., et al., Does Relative Energy Deficiency in Sport (REDs) Syndrome Exist? Sports Med, 2024. 54(11): p. 2793–2816.
  8. De Souza, M.J., et al., Randomised controlled trial of the effects of increased energy intake on menstrual recovery in exercising women with menstrual disturbances: the 'REFUEL' study. Hum Reprod, 2021. 36(8): p. 2285–2297.
  9. Lieberman, J.L., et al., Menstrual Disruption with Exercise Is Not Linked to an Energy Availability Threshold. Med Sci Sports Exerc, 2018. 50(3): p. 551–561.
  10. Isola, V., et al., Changes in hormonal profiles during competition preparation in physique athletes. Eur J Appl Physiol, 2024.
  11. Fagerberg, P., Negative Consequences of Low Energy Availability in Natural Male Bodybuilding: A Review. Int J Sport Nutr Exerc Metab, 2018. 28(4): p. 385–402.
  12. Koehler, K., et al., Low energy availability in exercising men is associated with reduced leptin and insulin but not with changes in other metabolic hormones. J Sports Sci, 2016. 34(20): p. 1921–9.
  13. Jurov, I., N. Keay, and S. Rauter, Severe Reduction of Energy Availability in Controlled Conditions Causes Poor Endurance Performance, Impairs Explosive Power and Affects Hormonal Status in Trained Male Endurance Athletes. Applied Sciences, 2021. 11(18): p. 8618.
  14. Jurov, I., N. Keay, and S. Rauter, Reducing energy availability in male endurance athletes: a randomized trial with a three-step energy reduction. J Int Soc Sports Nutr, 2022. 19(1): p. 179–195.
  15. Longland, T.M., et al., Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr, 2016. 103(3): p. 738–46.
  16. Hickey, M.S., et al., Leptin is related to body fat content in male distance runners. Am J Physiol, 1996. 271(5 Pt 1): p. E938–40.
  17. Murphy, C., L.D.D. Bilek, and K. Koehler, Low Energy Availability with and without a High-Protein Diet Suppresses Bone Formation and Increases Bone Resorption in Men: A Randomized Controlled Pilot Study. Nutrients, 2021. 13(3).
  18. Ojanen, T., P. Jalanko, and H. Kyrolainen, Physical fitness, hormonal, and immunological responses during prolonged military field training. Physiol Rep, 2018. 6(17): p. e13850.
  19. Jurimae, J., J. Maestu, and T. Jurimae, Leptin as a marker of training stress in highly trained male rowers? Eur J Appl Physiol, 2003. 90(5-6): p. 533–8.
  20. Papageorgiou, M., et al., Effects of reduced energy availability on bone metabolism in women and men. Bone, 2017. 105: p. 191–199.
  21. Friedl, K.E., et al., Endocrine markers of semistarvation in healthy lean men in a multistressor environment. J Appl Physiol (1985), 2000. 88(5): p. 1820–30.
  22. Hilton, L.K. and A.B. Loucks, Low energy availability, not exercise stress, suppresses the diurnal rhythm of leptin in healthy young women. Am J Physiol Endocrinol Metab, 2000. 278(1): p. E43–9.
  23. Isola, V., et al., Weight loss induces changes in adaptive thermogenesis in female and male physique athletes. Appl Physiol Nutr Metab, 2023. 48(4): p. 307–320.
  24. Schaal, K., et al., Decreased energy availability during training overload is associated with non-functional overreaching and suppressed ovarian function in female runners. Appl Physiol Nutr Metab, 2021. 46(10): p. 1179–1188.
  25. Jurov, I., et al., Inducing low energy availability in trained endurance male athletes results in poorer explosive power. Eur J Appl Physiol, 2022. 122(2): p. 503–513.
  26. Kojima, C., et al., Muscle Glycogen Content during Endurance Training under Low Energy Availability. Med Sci Sports Exerc, 2020. 52(1): p. 187–195.
  27. Loucks, A.B. and M. Verdun, Slow restoration of LH pulsatility by refeeding in energetically disrupted women. Am J Physiol, 1998. 275(4): p. R1218–26.
  28. Papageorgiou, M., et al., Bone metabolic responses to low energy availability achieved by diet or exercise in active eumenorrheic women. Bone, 2018. 114: p. 181–188.
  29. Henning, P.C., et al., Recovery of endocrine and inflammatory mediators following an extended energy deficit. J Clin Endocrinol Metab, 2014. 99(3): p. 956–64.
  30. McGuire, A., et al., Measurement of energy availability in highly trained male endurance athletes and examination of its associations with bone health and endocrine function. Eur J Nutr, 2024. 63(7): p. 2655–2665.
  31. Hamarsland, H., et al., Depressed Physical Performance Outlasts Hormonal Disturbances after Military Training. Med Sci Sports Exerc, 2018. 50(10): p. 2076–2084.
  32. Hulmi, J.J., et al., The Effects of Intensive Weight Reduction on Body Composition and Serum Hormones in Female Fitness Competitors. Front Physiol, 2016. 7: p. 689.
  33. Kyrolainen, H., et al., Hormonal responses during a prolonged military field exercise with variable exercise intensity. Eur J Appl Physiol, 2008. 102(5): p. 539–46.
  34. Hooper, D.R., et al., The presence of symptoms of testosterone deficiency in the exercise-hypogonadal male condition and the role of nutrition. Eur J Appl Physiol, 2017. 117(7): p. 1349–1357.
  35. Hennigar, S.R., et al., Testosterone Administration During Energy Deficit Suppresses Hepcidin and Increases Iron Availability for Erythropoiesis. J Clin Endocrinol Metab, 2020. 105(4).
  36. Loucks, A.B. and E.M. Heath, Induction of low-T3 syndrome in exercising women occurs at a threshold of energy availability. Am J Physiol, 1994. 266(3 Pt 2): p. R817–23.
  37. Loucks, A.B. and R. Callister, Induction and prevention of low-T3 syndrome in exercising women. Am J Physiol, 1993. 264(5 Pt 2): p. R924–30.
  38. Tokuyama, M., et al., Possible Association of Energy Availability with Transferrin Saturation and Serum Iron during Summer Camp in Male Collegiate Rugby Players. Nutrients, 2021. 13(9).
  39. Sarin, H.V., et al., Molecular Pathways Mediating Immunosuppression in Response to Prolonged Intensive Physical Training, Low-Energy Availability, and Intensive Weight Loss. Front Immunol, 2019. 10: p. 907.
  40. Hutson, M.J., et al., Effects of Low Energy Availability on Bone Health in Endurance Athletes and High-Impact Exercise as A Potential Countermeasure: A Narrative Review. Sports Med, 2021. 51(3): p. 391–403.
  41. Ihle, R. and A.B. Loucks, Dose-response relationships between energy availability and bone turnover in young exercising women. J Bone Miner Res, 2004. 19(8): p. 1231–40.
  42. Ikegami, N., et al., The Influence of Low Energy Availability on Bone Mineral Density and Trabecular Bone Microarchitecture of Pubescent Female Athletes: A Preliminary Study. Int J Environ Res Public Health, 2022. 19(9).
  43. Ackerman, K.E., et al., Low energy availability surrogates correlate with health and performance consequences of Relative Energy Deficiency in Sport. Br J Sports Med, 2018.
  44. Haines, M.S., et al., Male Runners With Lower Energy Availability Have Impaired Skeletal Integrity Compared to Nonathletes. J Clin Endocrinol Metab, 2023. 108(10): p. e1063–e1073.
  45. 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 (1985), 1998. 84(1): p. 37–46.
  46. Jouhki, I., et al., Effects of fat loss and low energy availability on the serum cardiometabolic profile of physique athletes. Scand J Med Sci Sports, 2024. 34(1): p. e14553.
  47. Matkin-Hussey, P., et al., RED-S: A Review of the Screening, Diagnosis, Treatment, and Recovery. Strength & Conditioning Journal, 2023. 46.
  48. Rudin, R., et al., Exploring different interventions for Relative Energy Deficiency in Sport (REDs): A systematic review. JSAMS Plus, 2025. 5: p. 100085.