Relative Energy Deficiency in Sport (RED-S)

What is Relative Energy Deficiency in Sport?

RED-S can occur when an athlete’s energy intake (food + drink) consistently falls short of the energy needed for training, daily living, growth and recovery. In other words, there isn’t enough “fuel left over” after exercise to support essential body functions like metabolism, bone maintenance, immune health, hormone production, and tissue repair.
Low energy availability (LEA) can happen deliberately (e.g. overly restrictive eating, intentional weight loss) or unintentionally (e.g. high training load and inadequate fuelling, poor meal planning or timing).
Importantly, RED-S can affect any athlete – regardless of sex, age or performance level.

Who is at Risk?

• Athletes engaged in endurance, aesthetic, weight-category or leanness-focused sports (e.g. running, cycling, gymnastics, dancing, rowing, combat sports).
• Individuals with high training volumes or sudden increases in training load (especially without corresponding increases in fuelling).
• Athletes who under-fuel unintentionally due to lack of appetite, time, knowledge, or access to appropriate meals; common especially in busy schedules or adolescence.
• Athletes who intentionally restrict food intake or engage in disordered eating patterns to manage weight or body composition.
• Growing adolescents: puberty and development increase energy and nutrient needs, making them especially vulnerable.

Common Signs & Symptoms

RED-S may present in many different ways. Symptoms can be subtle at first, and because the body shifts energy away from “non-essential” functions, problems may develop quietly over time. 

Possible signs to watch for:

• Persistent fatigue, lack of energy, or poor recovery between sessions
• Frequent illness or infections, poor immunity
• Recurring injuries and delayed healing
• Reduced performance: decreased endurance, strength loss, slower recovery, inability to improve despite training
• For females: menstrual disturbances (irregular periods, loss of period)
• For males: hormonal consequences (e.g. reduced testosterone), low libido or changes in mood/drive.
• Poor bone health over time: decreased bone mineral density, higher risk of fractures or osteoporosis.
• Negative impact on metabolism, cardiovascular health, immune function, digestion, and general well-being.

Health & Performance Consequences

When the body is chronically under-fuelled:

• Bone health suffers:
  • Poor bone mineralisation in adolescence or low bone density in adulthood, leading to stress fractures or early onset bone disease.
• Hormonal disruption:
  • Menstrual dysfunction in women, decreased sex hormones and libido in men, which can affect long-term reproductive health and bone maintenance. 
• Impaired recovery & muscle/tissue repair issues:
  • Protein synthesis, tissue repair and immune function are compromised.
• Reduced performance potential:
  • Fatigue, reduced strength or endurance, decreased training response, risk of injury or overuse injuries.
• Long-term health risks:
  • Potential for irreversible bone damage, hormonal imbalance, metabolic disruption, impaired growth (especially in adolescents), and compromised general health.

What Causes RED-S?

At the core, RED-S stems from low energy availability (LEA), not enough energy/breakdown between energy in from food and energy out from exercise and daily living. 

Common contributing factors include:

• High training volumes or sudden increases in training load without adjusting food intake appropriately.
• Inadequate meal planning, poor access to food, lack of nutrition education or time constraints (common in busy adolescents or student-athletes).
• Intentional dietary restriction (e.g. for weight management, lean physique, aesthetics). 
• Disordered eating behaviours or clinical eating disorders, though RED-S can occur without them.
• Increased energy requirements during growth or puberty (adolescents), which may not be matched with increased energy intake. 

How to Prevent & Manage RED-S

The role of a Sports Dietitian:

1. Assess energy needs vs intake – calculating the energy demands for training, growth, living, then ensuring nutrition plans meet those demands.
2. Plan fuel around training and daily life: Meal timing, balanced macronutrients, ensuring adequate total energy, micronutrients, hydration.
3. Educate athletes, parents, and coaches by raising awareness that under-fueling may be unintentional, and educating on realistic nutrition strategies for performance and health.
4. Monitor health and performance markers
5. Coordinate with health and support professionals when needed, for example medical doctors, physiotherapists, psychologists, especially if there’s prolonged energy deficit, disordered eating, or bone/ hormonal concerns.
6. Support safe return to energy balance and performance with an emphasis on long-term health, not short-term weight or appearance goals.
   

When to Seek Help?

If you or an athlete you support shows any combination of the following over a sustained period, it’s worth booking an appointment:

• Persistent fatigue, poor recovery, or declining performance despite training
• Recurrent injuries, frequent illness
• Changes in mood, motivation, concentration, sleep
• For female athletes: irregular or absent periods; for male athletes: unexplained low energy, low libido or hormonal concerns
• Difficulty maintaining body mass or unintended weight loss or conversely, restriction of food intake or signs of disordered eating
• Growing adolescents who seem ‘flat’, fatigued, or not thriving despite training

---

Visit our Dietitian page to find out more!

---

Book in with the Coast Sport team today!