Understanding Low Energy Availability (LEA)
Low energy availability (LEA) occurs when an individual, particularly an athlete, does not consume enough calories to cover the energy expended during daily life and exercise. The remaining energy available for essential bodily functions—such as metabolism, reproduction, bone health, and immunity—is compromised. This deficit can happen unintentionally, due to a lack of nutritional knowledge or mismanaged training, or intentionally, often driven by a desire for a low body weight in weight-sensitive or aesthetic sports. The consequences of LEA extend beyond simple fatigue, affecting multiple physiological systems and potentially leading to the broader syndrome known as Relative Energy Deficiency in Sport (RED-S).
The Health Consequences of LEA
The risks associated with LEA are extensive and affect nearly every system of the body. When the body perceives a state of energy deficit, it initiates a series of metabolic adaptations to conserve energy for only the most vital functions. This often means sacrificing energy-intensive processes like reproduction, growth, and immune function.
- Skeletal Health: LEA is a major risk factor for compromised bone health. Hormonal changes, such as reduced estrogen in females and testosterone in males, negatively impact bone mineral density (BMD), increasing the risk of stress fractures and osteoporosis later in life. In fact, one study found that female runners with risk factors for the Female Athlete Triad (related to LEA) had a nine times higher risk of bone fractures.
- Endocrine and Reproductive Function: LEA profoundly disrupts the endocrine system. It suppresses key hormones like thyroid hormones (T3), leptin, insulin, and insulin-like growth factor-1 (IGF-1). In females, this can lead to menstrual dysfunction, including irregular periods or complete absence of menstruation (amenorrhea). In males, it can cause suppressed testosterone levels and decreased libido.
- Cardiovascular Health: Long-term LEA can lead to cardiovascular issues. Altered cholesterol levels, despite a state of low energy, have been observed and may be detrimental to heart health over time. A reduced resting heart rate can also occur as the body slows down to conserve energy, potentially causing dizziness.
- Gastrointestinal (GI) Function: Many athletes experiencing LEA report GI distress, including bloating, constipation, and general stomach pain. This is often due to the body slowing down the digestive process to save energy.
- Immune System: A consistent energy deficit can suppress the immune system, leaving athletes more vulnerable to recurrent illnesses like colds and infections. The energy required for proper immune cell function is re-routed elsewhere, weakening the body's defenses.
- Psychological and Mental Health: LEA has significant mental health implications. Athletes may experience mood disturbances, irritability, increased anxiety, and depression. Poor concentration and impaired judgment are also common, which can affect performance and safety during training.
Impact on Athletic Performance and Recovery
While some athletes may initially experience a weight loss-related boost in performance in certain sports, prolonged LEA invariably leads to compromised athletic function and training adaptations.
Common Performance-Related Risks include:
- Decreased Muscle Strength and Endurance: Reduced muscle protein synthesis and suboptimal energy substrate levels (like glycogen) impair the body's ability to maintain muscle mass and strength, particularly important for power athletes.
- Impaired Recovery: The energy required for muscle repair and training adaptation is insufficient, leading to prolonged recovery times and increased fatigue. This creates a vicious cycle of under-fueling and poor performance.
- Increased Injury Risk: Aside from reduced bone mineral density leading to stress fractures, impaired collagen synthesis can also challenge the integrity of ligaments and tendons, further elevating injury risk. Chronic fatigue can also contribute to improper form and technique, leading to injury.
- Decreased Training Response: The body is unable to properly adapt and improve in response to training stimuli. As a result, athletes may experience performance plateaus or a decline in their athletic capabilities.
- Poor Neuromuscular Function: LEA can affect the brain's ability to supply the nervous system and muscles with enough energy for efficient motor control. This can manifest as decreased coordination, slower reaction times, and impaired judgment.
Short-Term vs. Chronic LEA Effects
LEA can be categorized into acute (short-term) and chronic phases, each with distinct physiological responses and potential health outcomes. The body's initial response is to trigger immediate hormonal shifts, while prolonged exposure leads to more serious, systemic adaptations.
| Feature | Short-Term LEA (Days to ~2 Weeks) | Chronic LEA (Weeks to Months/Years) |
|---|---|---|
| Hormonal Changes | Decreased T3, IGF-1, insulin, leptin; Increased cortisol. Disruptions in LH pulse (females). | Sustained decreases in T3, IGF-1, leptin, insulin, estradiol (females), and testosterone (males). Increased ghrelin. |
| Metabolic Response | Reduced muscle protein synthesis, muscle glycogen depletion, increased fat oxidation. Impaired glucose handling. | Significant metabolic adaptation, including a consistently suppressed resting metabolic rate (RMR). Reduced ability to effectively utilize nutrients. |
| Reproductive Impact | Subtle disruptions in hormone pulsatility (e.g., LH). Less noticeable effects initially. | Functional hypothalamic amenorrhea (females) and sustained low testosterone/libido (males) due to suppression of the reproductive axis. |
| Bone Health | Early changes in bone turnover markers (decreased formation, increased resorption). Not yet reflected in BMD scans. | Progressive decrease in bone mineral density. Increased risk of stress fractures and potential for long-term osteoporosis. |
| Mental State | Potential for increased negative mood states like irritability or tension. | Mood disturbances can worsen, leading to increased anxiety and depression. |
Preventing and Addressing Low Energy Availability
Preventing LEA requires a proactive approach focused on education, proper fueling strategies, and recognizing the signs of under-fueling. Athletes, coaches, and sports medical staff must work together to ensure health is prioritized over body weight ideals.
Actionable steps include:
- Prioritize Energy Intake: Consume enough calories to match daily energy expenditure, especially during periods of high training load. This requires understanding your sport's energy demands and your individual needs.
- Strategic Fuelling: Ensure adequate carbohydrate intake before, during, and after exercise to support glycogen stores and provide readily available energy. Do not fear carbohydrates.
- Balanced Nutrition: Consume a variety of nutrient-dense foods from all food groups. Focusing on one macronutrient or eliminating food groups without professional guidance increases the risk of LEA.
- Listen to Your Body: Pay attention to hunger cues, mood changes, and fatigue levels. Excessive hunger or an absence of hunger cues are both potential indicators of LEA.
- Seek Expert Help: Consult with a sports dietitian or physician if you suspect LEA or have symptoms. Professional guidance is critical for proper diagnosis and recovery.
- Avoid Weight-Related Pressure: Challenge the belief that a lower body weight automatically leads to better performance. In many cases, healthy body composition is more beneficial than extreme leanness.
- Monitor Your Menstrual Cycle: For females, tracking menstrual regularity is a key indicator of energy status. Any changes should be discussed with a doctor.
For more detailed information on understanding LEA and its impact, resources like the articles from the National Institutes of Health provide valuable insights, such as this review on Identifying and Analyzing Low Energy Availability in Athletes.
Conclusion
The risks of low energy availability are far-reaching and can have devastating consequences for an athlete's health and performance. From compromising bone density and reproductive health to impairing the immune system and mental well-being, the body's adaptive response to insufficient fueling is a serious concern. While the initial drop in performance might be masked or even delayed, chronic LEA will ultimately undermine an athlete's ability to train effectively and compete at their best. By focusing on education and prioritizing adequate energy intake, athletes and their support systems can mitigate these risks and foster a healthier, more sustainable approach to sport.
