What Is Low Energy Availability (LEA)?
Low energy availability (LEA) describes a state where an individual's energy intake, primarily from food, is insufficient to meet the body's energy demands for exercise and daily physiological functions. This energy deficit is calculated by subtracting the calories burned during exercise from the calories consumed, with the remainder being the energy available for fundamental bodily processes. LEA is a spectrum, ranging from mild and temporary to severe and chronic. The most severe forms of LEA are often tied to Relative Energy Deficiency in Sport (RED-S), a syndrome that encompasses a wide array of health and performance issues resulting from chronic energy deficit. LEA can occur intentionally through restrictive eating habits, often stemming from body image dissatisfaction or a perceived need for leanness. Conversely, it can be unintentional, arising from a lack of nutritional knowledge, poor meal planning, or a sudden increase in training intensity without a corresponding increase in caloric intake. Athletes in weight-sensitive or high-endurance sports are particularly vulnerable.
The Body’s Adaptation to Energy Scarcity
In response to low energy availability, the body enters a state of survival mode, conserving energy by down-regulating or shutting down non-essential bodily functions. It prioritizes energy for the most vital organs, leaving other systems under-fueled and compromised. This adaptive response is what leads to the cascade of negative health consequences associated with LEA, extending far beyond simple weight loss.
How LEA Affects Your Health
Low energy availability has wide-ranging and serious effects on virtually every system in the body. The chronic stress of under-fueling perturbs delicate metabolic and hormonal balances, leading to physiological dysfunction.
Hormonal Dysregulation
One of the most immediate and significant impacts of LEA is hormonal disruption. This can affect:
- Reproductive hormones: In females, LEA suppresses the hypothalamic-pituitary-gonadal (HPG) axis, leading to decreased luteinizing hormone (LH) and estrogen levels, which can cause menstrual irregularities or amenorrhea (absence of periods). In males, it can reduce testosterone levels and libido.
- Thyroid hormones: LEA can decrease thyroid hormone (T3) levels, which slows the body's metabolism and energy expenditure in an attempt to conserve energy.
- Leptin and Ghrelin: Leptin, which regulates appetite and energy balance, decreases, while ghrelin, the "hunger hormone," may increase. This dysregulation can intensify hunger cues.
- Cortisol: Levels of the stress hormone cortisol may rise, contributing to increased anxiety and protein breakdown.
Compromised Bone Health
Bone tissue is dynamic and constantly being remodeled. LEA, primarily through hormonal imbalances, severely disrupts this process. Reduced estrogen and testosterone directly inhibit bone formation and accelerate bone resorption. This leads to decreased bone mineral density (BMD) and a significantly higher risk of stress fractures and osteoporosis. The consequences are particularly severe for young athletes, as most of their peak bone mass is accrued before age 25, and damage during this period can have irreversible lifelong implications.
Suppressed Immune Function
In a state of energy deficit, the body reallocates energy away from less critical functions, including the immune system. This compromises the body's ability to fight off infections, leading to frequent illnesses like colds and flu. Athletes with LEA report higher rates of upper respiratory tract infections and longer recovery times from illness.
Psychological and Cognitive Impacts
The effects of LEA are not limited to physical health; they also manifest psychologically. Athletes may experience poor concentration, irritability, depression, anxiety, and a loss of motivation. This can negatively impact performance and overall mental well-being.
Cardiovascular and Metabolic Health
LEA can lead to a dangerously low resting heart rate as the body conserves energy, which in severe cases can damage the heart. Metabolically, it causes impaired glucose tolerance, altered lipid profiles (e.g., higher cholesterol), and depletes glycogen stores.
The Impact on Athletic Performance
While some athletes may pursue LEA in the belief it will enhance performance, the opposite is almost always true in the long run. Any initial perceived performance boost from weight loss is eventually negated by the physiological impairments. Performance-related consequences of LEA include:
- Decreased muscle strength and power.
- Reduced endurance and increased fatigue.
- Impaired coordination and concentration.
- Decreased training response, meaning the body cannot adapt and build from training stimulus.
- Increased risk of injury and longer recovery times.
Signs, Symptoms, and Diagnosis
Diagnosis of LEA and RED-S requires a thorough clinical assessment, often involving a multi-disciplinary team. Key indicators include:
- Physical: Excessive fatigue, recurrent injuries (especially stress fractures), frequent illnesses, persistent hunger, cold intolerance, and gastrointestinal issues like constipation.
- Hormonal/Reproductive: Irregular or absent menstrual periods (females), or low libido (males).
- Mental/Behavioral: Poor concentration, mood swings, irritability, anxiety, and a loss of motivation.
Comparison: Healthy vs. Low Energy Availability
| Feature | Healthy Energy Availability (EA > 45 kcal/kg FFM/day) | Low Energy Availability (EA < 30 kcal/kg FFM/day) |
|---|---|---|
| Metabolic Rate | Normal to high resting metabolic rate | Suppressed or reduced resting metabolic rate |
| Hormonal Profile | Balanced reproductive, thyroid, and growth hormones | Decreased estrogen/testosterone, T3, leptin; increased cortisol |
| Bone Health | Strong bone mineral density, low fracture risk | Low bone mineral density, high risk of stress fractures |
| Immune System | Robust immune function, less illness | Weakened immunity, increased risk of illness |
| Athletic Performance | Optimized strength, endurance, and recovery | Decreased strength, endurance, and poor recovery |
| Psychological State | Stable mood, good concentration, low anxiety | Irritability, mood swings, depression, brain fog |
Recovery and Prevention Strategies
Addressing and preventing LEA requires a multi-faceted approach. A sports dietitian or a medical professional is crucial to help create a nutrition plan that supports training and daily needs.
Practical Steps to Mitigate LEA
- Increase Energy Intake: Ensure calorie intake matches energy expenditure, especially during periods of high training load. This may involve increasing meal frequency or adding nutritious snacks throughout the day.
- Optimize Meal Timing: Prioritize nutrient intake before, during, and after exercise to fuel and recover effectively. Focus on carbohydrates and protein post-workout.
- Plan Ahead: During intense training cycles or travel, having a pre-planned nutrition strategy can prevent accidental under-fueling.
- Reduce Exercise Load: In some cases, reducing training volume or intensity is necessary to allow the body to recover and restore energy balance.
- Seek Professional Guidance: Work with a team of professionals—dietitians, sports physicians, and psychologists—to manage nutrition and address any underlying psychological issues.
- Listen to Your Body: Pay attention to early warning signs like persistent fatigue, poor recovery, and mood changes, which indicate the need for intervention.
For more information on the wide range of effects, the International Olympic Committee published an extensive review on RED-S that is highly recommended for athletes, coaches, and practitioners.
Conclusion
Low energy availability is a serious and widespread condition, particularly among active individuals, with consequences that extend far beyond athletic performance. By altering metabolic, hormonal, and psychological functions, LEA can lead to significant and potentially long-lasting health problems, including reduced bone density and compromised immune function. Recognizing the signs and symptoms early and implementing proper fueling and recovery strategies are critical steps toward prevention and recovery. Professional guidance from a multi-disciplinary team is often necessary to safely and effectively restore energy balance and optimize long-term health.
Disclaimer: The information provided is for educational purposes only and is not a substitute for professional medical advice. Always consult with a qualified healthcare provider for any health concerns or before making any dietary changes.
