Understanding Low Energy Availability (LEA) and RED-S
Low energy availability (LEA) is a state where the body's caloric intake is insufficient to cover the energy expended during physical activity and the needs for normal bodily function. This can happen intentionally through restrictive dieting or unintentionally due to a lack of nutritional knowledge or appetite suppression from exercise. When this energy deficit is chronic, it leads to a cascade of physiological and psychological issues known as Relative Energy Deficiency in Sport (RED-S). While historically framed around female athletes as the "Female Athlete Triad" (low energy availability, menstrual dysfunction, and low bone mineral density), the RED-S model now recognizes that these consequences affect all genders.
LEA is not always indicated by weight loss, as the body can adapt by slowing down its metabolic processes to conserve energy. However, this adaptive response comes at a heavy cost to nearly every system in the body.
Hormonal and Metabolic Consequences
One of the most immediate and impactful effects of low energy availability is the disruption of the endocrine system. The body interprets a severe caloric deficit as a threat, triggering a survival response that downregulates non-essential functions.
Sex Hormone Imbalance
In females, LEA suppresses the hypothalamic-pituitary-gonadal (HPG) axis, leading to menstrual dysfunction, such as irregular periods (oligomenorrhea) or complete absence of periods (amenorrhea). This is not due to low body fat but is a direct result of energy deficiency. The associated low estrogen levels have far-reaching negative effects. In male athletes, chronic LEA can cause a decrease in testosterone levels, affecting libido and overall strength.
Thyroid and Stress Hormone Changes
To conserve energy, the body reduces its metabolic rate. This is partly mediated by decreased levels of thyroid hormones (T3 and T4). Simultaneously, stress hormones, such as cortisol, may increase. Elevated cortisol can further suppress the reproductive axis and negatively impact bone health.
Altered Metabolism
Metabolically, low energy availability impairs the body's ability to regulate glucose and fat utilization.
- Impaired Glucose Regulation: Studies show that after only a few days of LEA, the body's ability to clear glucose from the bloodstream becomes impaired. This is because essential functions, like powering the brain, compete with muscles for available glucose.
- Metabolic Slowdown: The resting metabolic rate (RMR), the energy your body burns at rest, can significantly decrease as an adaptation to chronic low energy intake.
- Fatigue: These metabolic shifts contribute directly to feelings of chronic fatigue, leaving athletes feeling sluggish despite training hard.
Compromised Skeletal Health
Perhaps one of the most serious long-term effects of low energy availability is its impact on bone health, which can lead to irreversible damage if not addressed early.
Decreased Bone Mineral Density (BMD)
LEA disrupts the normal bone remodeling process, a constant cycle of resorption and formation. The hormonal changes, particularly low estrogen, impair the function of osteoblasts (bone-forming cells). This can result in:
- Low Bone Mineral Density: Over time, the balance shifts towards more bone breakdown than formation, leading to osteopenia and, eventually, osteoporosis. This is especially critical during adolescence and young adulthood, when peak bone mass is being built.
- Increased Fracture Risk: The weakened bone structure significantly increases the risk of stress fractures and other bone injuries. Some studies show that athletes with low energy availability have a 2 to 4 times greater risk of stress fractures compared to their healthy counterparts.
Long-Term Consequences
For young athletes, damage to bone density during key developmental years can have lifelong implications, as the opportunity to achieve peak bone mass may be lost forever.
Impaired Immune and Psychological Function
LEA's effects are not limited to physical systems; mental and immune health are also severely compromised.
Weakened Immunity
The energy-conserving state of LEA impairs immune function, making athletes more susceptible to frequent illnesses like colds and upper respiratory infections. A high incidence of sickness can disrupt training and further impact performance.
Psychological Issues
Low energy availability is strongly correlated with psychological symptoms, including:
- Mood Changes: Irritability, depression, and anxiety are common due to the hormonal shifts and the psychological stress of dieting or performance pressure.
- Impaired Cognitive Function: Athletes may experience decreased concentration, impaired judgment, and coordination issues, which directly affect performance and safety.
- Distorted Body Image: The pressure to be lean can lead to body dissatisfaction and, in some cases, the development of disordered eating.
Effects on Performance and Training
While some athletes may pursue LEA in the mistaken belief it will enhance performance, the long-term reality is detrimental.
Decreased Performance and Training Response
Initially, a reduction in body weight may offer a short-term advantage in weight-sensitive sports. However, prolonged LEA ultimately depletes energy stores, leading to decreased endurance, muscle strength, and power. Athletes experience a decreased response to training stimulus, meaning their hard work produces diminishing returns.
Increased Risk of Injury
The combination of weakened bones and impaired muscle recovery drastically increases the risk of injury. These injuries can be chronic or recurrent, forcing athletes to take extended time off, further exacerbating the negative physical and mental health cycle.
Diagnosis and Management
Early detection and intervention are critical for managing and reversing the effects of low energy availability.
Multidisciplinary Approach
The best approach involves a multidisciplinary team, including a sports physician, registered dietitian, and mental health counselor. Screening tools, such as the Low Energy Availability in Females Questionnaire (LEAF-Q), can help identify athletes at risk.
Treatment Plan
Management focuses on two main strategies: increasing energy intake and, if necessary, reducing energy expenditure.
- Nutritional Intervention: Working with a sports dietitian is key to creating a sustainable eating plan that meets the body's caloric and nutrient needs.
- Modified Training: In some cases, a temporary reduction in training volume and intensity is necessary to allow the body to recover.
Comparison of Short-term vs. Long-term LEA Effects
| Feature | Short-Term LEA Effects | Long-Term LEA Effects |
|---|---|---|
| Metabolism | Shifts in fuel utilization (more fat, less glucose). | Significantly suppressed resting metabolic rate. |
| Hormones | Suppression of key hormones like leptin and insulin. | Chronic hormonal disruption (sex hormones, thyroid, cortisol). |
| Skeletal Health | Initial changes in bone metabolism. | Decreased bone mineral density (osteopenia/osteoporosis) and increased stress fractures. |
| Reproduction | Subtle menstrual disturbances (luteal phase defects) or low libido. | Functional hypothalamic amenorrhea in females; significant testosterone reduction in males. |
| Immunity | Increased likelihood of illness like colds and flu. | Chronically weakened immune response. |
| Psychology | Irritability, mood swings. | Increased risk of anxiety, depression, and disordered eating. |
| Performance | Can be masked by weight loss but often leads to early fatigue. | Decreased endurance, strength, and impaired training response. |
Conclusion
Low energy availability is a complex and dangerous condition that poses significant risks to health and athletic performance across all body systems. The physiological adaptations, while serving as a survival mechanism, lead to serious, potentially irreversible consequences, especially concerning bone health during formative years. For athletes, coaches, and medical professionals, awareness and early detection are vital. By understanding the wide-ranging negative effects of low energy availability and implementing a comprehensive, multidisciplinary treatment plan focused on restoring proper nutrition, athletes can protect their long-term health and achieve sustainable, optimal performance.
For more in-depth information on Relative Energy Deficiency in Sport, consider reviewing the International Olympic Committee consensus statement.(https://www.ausport.gov.au/ais/nutrition/additional-resources)
