Early Signs of RED-S in Athletes
- Megan Whitehouse
- May 16
- 5 min read
If you’re an athlete, a coach, or someone passionate about fitness, understanding Relative Energy Deficiency in Sport (RED-S) is vital to supporting long-term health and performance. RED-S is a condition that occurs when there’s an energy imbalance with food coming in and energy going out -essentially, when an athlete isn’t consuming enough energy (calories) to meet the demands of their training and daily life.
While RED-S can affect athletes of any gender, age, or sport, it’s often overlooked in its early stages. Catching the early signs of RED-S is critical to preventing more serious health consequences down the line. In this guide, we’ll explore how to spot those early red flags and what steps to take if RED-S is suspected.
What Is RED-S?
Relative Energy Deficiency in Sport (RED-S) is a term coined by the International Olympic Committee to describe a syndrome that results from low energy availability. This energy shortfall can happen unintentionally (due to increased training load without matching nutritional intake) or intentionally (through restrictive eating or disordered eating behaviors).
Why RED-S Matters?
RED-S affects more than just weight or appearance. It disrupts critical body systems including:
Hormonal balance
Menstrual function
Bone health
Metabolic rate
Immunity
Cardiovascular health
Psychological health
These widespread effects mean that RED-S is more than a nutrition issue - it’s a whole-body health risk.
Common Early Signs of RED-S
Recognising the early signs of RED-S is key to preventing irreversible health damage. Here are some warning signs to look for:
One of the earliest red flags is persistent fatigue, even after adequate rest. Athletes may feel sluggish, have less motivation to train, or experience an overall drop in daily energy levels.
Look out for:
Struggling to complete workouts
Feeling “drained” during or after training
Needing more naps or rest days than usual
RED-S and fatigue are closely connected, as the body begins to slow down to conserve energy. Without enough fuel, even everyday activities can feel exhausting.
2. Decline in Athletic Performance
A dip in performance is a clear warning. RED-S and performance decline go hand-in-hand because the body lacks the fuel it needs to build muscle, recover properly, and train effectively.
Signs include:
Plateaus or regressions in strength, speed, or endurance
Longer recovery times
Frequent muscle soreness
Often, athletes may try to push harder in training, not realising that doing more with less fuel only worsens the energy deficit.
RED-S and menstrual dysfunction is a well-documented connection. For female athletes, irregular or absent periods can be a key early indicator of hormonal imbalance caused by low energy availability.
Warning signs include:
Irregular cycles
Amenorrhea (missed periods for 3+ months)
Changes in menstrual flow or symptoms
This isn’t just a fertility concern — menstrual irregularities also signal broader disruptions in bone health, metabolic function, and endocrine balance.
4. Frequent Illness or Injuries
RED-S and injury recovery issues are common because the immune system becomes compromised, and bones and tissues weaken.
Watch for:
Recurring colds or infections
Slow-healing injuries
Increased risk of fractures (especially stress fractures)
RED-S and bone health is a critical concern. When the body doesn’t get enough fuel, it starts diverting energy away from non-essential systems like reproductive and skeletal health.
5. Mood Changes and Poor Concentration
RED-S and mood changes often show up before physical symptoms become obvious. Emotional and cognitive shifts can signal that something’s off.
You might notice:
Increased irritability or anxiety
Trouble concentrating
Feelings of depression or hopelessness
These changes underscore the connection between RED-S and psychological health. Lack of nutrients, especially fats and carbohydrates, affects neurotransmitter production and brain function.
6. Disordered Eating Behaviors
Not all RED-S cases involve an eating disorder, but RED-S and eating disorders are closely linked. Athletes may begin to restrict calories, avoid certain food groups, or show an unhealthy obsession with “clean” eating.
Possible signs:
Skipping meals or snacks
Extreme guilt around food
Compulsive exercise habits
Disordered eating patterns are one of the most common pathways to RED-S. Recognising these behaviours early can prevent long-term health consequences.
The Health Risks of Ignoring RED-S
If left unchecked, RED-S can lead to serious and lasting health problems. Some of the long-term health risks of RED-S include:
Osteoporosis and bone fractures
Infertility
Poor cardiovascular health
Muscle loss
Suppressed immunity
Mood disorders and burnout
In many cases, these effects can persist long after training has stopped. That’s why early recognition is crucial - the sooner RED-S is addressed, the better the outcomes.
What to Do If You Suspect RED-S
Athletes require significantly more fuel than sedentary individuals. Proper intake of macronutrients (carbohydrates, fats, proteins) and micronutrients is essential.
Focus on:
Regular meals and snacks
Carbohydrate-rich meals around training
Adequate protein for recovery
Including fats for hormonal health
Meeting the nutritional needs for athletes is the foundation for health and performance. Nutrition isn’t just fuel - it’s medicine.
2. Seek a Proper RED-S Diagnosis
If RED-S is suspected, a sports dietitian can help with a thorough assessment. A RED-S diagnosis typically involves:
Medical history review
Blood tests (hormonal, iron, vitamin D, etc.)
Menstrual history (for women)
Bone density scans
It’s important not to self-diagnose. RED-S can mimic other health issues, so a professional evaluation is essential.
3. Begin RED-S Treatment with a Team Approach
RED-S treatment involves restoring energy balance through nutrition, adjusting training, and often addressing psychological health. An interdisciplinary team may include:
Physician
Sports psychologist or counselor
Athletic coach
The goal is full health restoration - not just getting back to training, but thriving mentally and physically.
Tips for Preventing RED-S
Preventing RED-S starts with awareness, education, and support. Here are a few practical tips:
Fuel properly before, during, and after workouts
Listen to your body -don’t ignore fatigue or irregular periods
Avoid under-fueling on rest days
Prioritize rest and recovery
Stay connected with coaches and healthcare providers
Promote RED-S awareness in athletic communities
Creating a culture of balance, health, and well-being in sports environments can help prevent RED-S from developing in the first place.
Top tips on recognising Early Signs of RED-S
What are the earliest warning signs of RED-S I should look out for?
Persistent fatigue
A noticeable drop in athletic performance
Mood swings
Irregular or missed periods
How can I tell the difference between overtraining and RED-S?
Overtraining and RED-S share symptoms like fatigue and poor performance, but RED-S includes additional signs such as hormonal imbalances, eating behaviours and mood disturbances. Overtraining can happen with adequate energy intake, while RED-S stems from consistent under-fueling.
What should I do if I think I have RED-S?
Reduce training intensity, increase energy intake, and seek professional help. A sports dietitian or doctor can confirm a RED-S diagnosis and recommend a treatment plan tailored to your specific needs. The earlier you take action, the faster you can recover.
Recognising the early signs of RED-S can make a world of difference in an athlete’s life.
At Nutrition & Co we want to help you achieve your full potential. Don't let
RED-S limit your performance and health-book a consultation with our specialist dietitians today!
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