Understanding the Core Cause: Low Energy Availability
Relative Energy Deficiency in Sport (RED-S) is fundamentally caused by low energy availability (LEA), which occurs when an athlete's dietary energy intake is insufficient to cover the energy expended during exercise, leaving inadequate energy for the body's normal physiological functions. Your body prioritizes energy for movement during exercise, and if there's not enough left over, non-essential functions like hormone production, bone health, and immune response are compromised. A state of LEA can develop intentionally, such as when an athlete consciously restricts food for performance or aesthetic reasons, or unintentionally, when an athlete simply doesn't eat enough to match a heavy training load.
Why Underweight Is Not a Prerequisite
Many people, including athletes and coaches, operate under the misconception that an athlete must be visibly underweight or have a low body fat percentage to develop RED-S. This is largely a holdover from the outdated "Female Athlete Triad" model, which focused specifically on disordered eating, amenorrhea, and osteoporosis in underweight females. However, the broader RED-S framework, introduced by the International Olympic Committee in 2014, recognizes that both males and females are at risk and that a wider spectrum of health consequences can occur at any body size. A person of normal weight can have RED-S because their body has adapted to a long-term energy deficit by slowing down its metabolism. This means they can maintain a seemingly stable weight while their body is operating in a state of chronic under-fueling, causing serious internal damage.
Symptoms That Can Occur at Any Weight
- Hormonal Disruption: In females, this can lead to irregular or absent menstrual cycles (functional hypothalamic amenorrhea), and in males, it can cause low testosterone and reduced libido.
- Bone Health Decline: Low bone mineral density can occur, increasing the risk of stress fractures and potentially leading to early-onset osteoporosis. This happens because the body conserves energy by reducing bone formation.
- Frequent Illness: A compromised immune system, weakened by the lack of energy, makes an athlete more susceptible to colds and infections.
- Gastrointestinal Issues: Symptoms like bloating and constipation are common as the body's digestive function is also impacted.
- Psychological Distress: Athletes with RED-S often experience mood changes, including increased irritability, anxiety, and depression.
- Decreased Performance: Despite continued training, an athlete with RED-S may experience reduced endurance, decreased muscle strength, impaired coordination, and poor recovery.
- Fatigue: Persistent, unexplained fatigue that doesn't improve with rest is a hallmark symptom.
Signs of RED-S at Normal Body Weight
| Indicator | Misconception vs. Reality |
|---|---|
| Visible Body Composition | Misconception: An athlete is a healthy weight, so they must be adequately fueled. Reality: The body can adapt to chronic low energy availability by slowing metabolism, preserving weight while compromising physiological functions. |
| Hormonal Function | Misconception: Regular periods mean a female athlete is healthy. Reality: Hormonal birth control can mask menstrual dysfunction caused by RED-S, and male athletes can experience low libido and testosterone without visible signs. |
| Mental State | Misconception: Mood swings are just part of being a high-level athlete. Reality: Increased anxiety, depression, and irritability are direct psychological consequences of the energy deficit affecting the brain. |
| Physical Performance | Misconception: Pushing harder will lead to a breakthrough. Reality: Decreased performance, slower recovery, and increased injury risk are signs the body is breaking down, not building up. |
The Dangers of Going Undiagnosed
The fact that RED-S can occur at a normal weight makes it a silent and dangerous condition. Athletes and coaches who look for weight loss as a primary sign can miss critical early indicators. This delay in diagnosis can allow the condition to progress and cause more severe, long-term health problems. For example, the loss of bone mineral density that occurs during adolescence and early adulthood due to RED-S can be irreversible, leading to a much higher risk of osteoporosis later in life. The psychological toll can be immense, as athletes struggle with conflicting desires to perform well and the physical and mental consequences of under-fueling. Early intervention, guided by a multidisciplinary team of sports dietitians, physicians, and mental health professionals, is essential for a full recovery.
Conclusion
The idea that you have to be underweight to have RED-S is a harmful misconception that prevents many athletes from getting the help they need. The syndrome is driven by a state of low energy availability, a chronic mismatch between caloric intake and exercise demands, which can manifest in athletes of any body size. From hormonal imbalances and decreased bone density to poor athletic performance and psychological distress, the wide-ranging health consequences underscore the importance of proper fueling and early recognition of symptoms, regardless of weight. The key to prevention and recovery lies in addressing the underlying energy deficit, not focusing on body size.
