Understanding the effects of low energy availability (LEA) on health and performance is crucial. LEA refers to the amount of dietary energy available for normal physiological function after subtracting exercise energy expenditure. It plays a significant role in the development of health and performance impairments as outlined in the 'triad' and RED-S models.

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The Evidence Short-Term Studies on LEA

Short-term laboratory-based studies have explored the acute effects of LEA. These well-controlled studies, lasting 3-5 days, primarily focused on young, sedentary females. Only one study directly examined the impact on endurance-type performance.Collectively, these studies support the notion that LEA affects hormonal and metabolic markers, leading to reproductive function impairment in females, bone metabolism disruptions, increased hunger, decreased resting metabolic rate, and reduced muscle protein synthesis.

However, the study assessing the effects of LEA on aerobic-type performance did not find any negative impact. It's important to note that changes in early markers of endocrine and physiological function may take longer than 3-5 days to manifest significant physiological disruptions affecting health and physical capacity. Therefore, it is challenging to predict the magnitude and duration of LEA required to cause substantial physiological disruption based solely on short-term studies.

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The Evidence Cross-Sectional Studies on LEA

The triad and RED-S models primarily rely on cross-sectional studies to support their claims. These studies compare populations believed to have been exposed to LEA with similar populations not exposed to LEA (e.g., amenorrheic vs. eumenorrheic athletes). Based on current evidence, these models suggest that LEA can result in various complications, including reduced bone density, impaired reproductive and immune function, cardiovascular and metabolic issues, gastrointestinal problems, and impaired performance.However, it's important to recognize that the duration of exposure to LEA in these cross-sectional studies remains unknown. Additionally, there may be other contributing factors, alongside LEA, that contribute to the health and performance impairments observed in different groups.

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Complications of Low Energy Availability

Current evidence indicates that LEA leads to a range of complications, such as reduced bone density, impaired reproductive and immune function, and compromised performance.

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The Limitations of Cross-Sectional Studies

Cross-sectional studies, despite their ecological validity, have limitations. While they are essential for scientific knowledge, they often lack control. As a result, we have a gap in understanding the effects of moderate exposure to LEA.

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Moderate Exposure to LEA and Physical Capacity

To fill some of the gaps in knowledge, our group conducted case studies that shed light on the effects of short-term exposure to LEA in specific training-nutrition interventions.In one case study, a male combat-sport athlete underwent an 8-week weight-making intervention, exposed to an average energy availability of 18 kcal/kg FFM/day. Despite the weight loss (~10 kg of body mass, ~5 kg of fat mass), both relative and absolute maximal aerobic capacity increased, along with lower and upper body strength. Another case study involved a male masters triathlete who improved his maximal aerobic power after recovering from surgery for a long-distance triathlon. Throughout the 18-week period, his energy availability was 29 kcal/kg FFM/day, resulting in a loss of ~5 kg of body mass (~2.5 kg fat mass).

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Conclusion

These preliminary findings suggest that well-planned training-nutrition interventions can enable individuals to manage intense training while experiencing energy availability that leads to weight loss. However, it's crucial to emphasize that we do not advocate for chronic or extreme weight-loss practices. It's essential to provide the right types and amounts of macronutrients at appropriate times. In certain sports, exposure toexposure to LEA, within controlled parameters, may be necessary and could yield positive performance outcomes.

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Scientific references

1. Areta JL, Taylor HL, Koehler K. Low energy availability: history, definition and evidence of its endocrine, metabolic and physiological effects in prospective studies in females and males. Eur J Appl Physiol. 2021;121:1–21.    
2. 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: 1st International Conference held in San Francisco, California, May 2012 and 2nd International Conference held in Indianapolis, Indiana, May 2013. British Journal of Sports Medicine. 2014;48:289–289.  
3. Langan-Evans C, Germaine M, Artukovic M, Oxborough DL, Areta JL, Close GL, et al. The Psychological and Physiological Consequences of Low Energy Availability in a Male Combat Sport Athlete. Medicine & Science in Sports & Exercise. 2021;53:673–83.    
4. Louis J, Tiollier E, Lamb A, Bontemps B, Areta J, Bernard T. Retraining and Nutritional Strategy of an Endurance Master Athlete Following Hip Arthroplasty: A Case Study. Front Sports Act Living. 2020;2:9.  
5. Mountjoy M, Sundgot-Borgen J, Burke L, Ackerman KE, Blauwet C, Constantini N, et al. International Olympic Committee (IOC) Consensus Statement on Relative Energy Deficiency in Sport (RED-S): 2018 Update. International Journal of Sport Nutrition and Exercise Metabolism. 2018;28:316–31.

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