Do I Have RED-S? 7 Early Signs Athletes Often Miss

sports nutritionRED-S
Written By Ashleigh Brunner

Feeling constantly tired? Struggling with recovery? Waking hungry overnight? These may be early Signs of RED-S — also known as Relative Energy Deficiency in Sport.

RED-S occurs when repeated Low Energy Availability (LEA) leaves the body without enough fuel to support both normal physiological function and training/exercise. Many athletes assume symptoms like fatigue, injuries, poor recovery, and hormonal changes are simply part of training hard — but they may actually be signs of chronic underfuelling in athletes.

Importantly, RED-S can occur both:

  • Intentionally — through deliberate restriction, dieting, body composition goals, or disordered eating.

  • Unintentionally — when athletes simply do not realise how much fuel their body actually needs to support training and recovery.

In simple terms your body does not have enough fuel left over to support:

  • Recovery

  • Hormones

  • Bone Health

  • Metabolism

  • Immune function

  • Performance

And importantly — you do not need to be underweight to experience RED-S.

Intentional vs Unintentional Underfueling in Athletes

Not all athletes with RED-S are intentionally restricting food.

Intentional Underfueling

This may involve:

  • Dieting for aesthetic goals

  • Fear of weight gain

  • Pursuit of a leaner physique

  • Disordered eating behaviours

  • Pressure from sport culture

  • Restricting carbohydrates or overall food intake

Unintentional Underfueling

This is extremely common, especially in busy or high-training athletes.

Examples include:

  • Not eating enough around training

  • Skipping meals due to time constraints

  • Poor appetite after exercise

  • Underestimating energy needs

  • High training loads with inadequate fuelling

  • Trying to eat “clean” but not enough

Many athletes with RED-S genuinely believe they are eating well.

1. Persistent Athlete Fatigue

One of the most common Signs of RED-S is ongoing fatigue that does not improve with rest.

This can look like:

  • Heavy legs

  • Brain fog

  • Low motivation

  • Exhaustion after training

  • Feeling flat during sessions

Persistent Athlete Fatigue is often one of the earliest signs of chronic Low Energy Availability.

2. Poor Recovery Between Training Sessions

If your recovery feels slower than it used to, your body may not have enough energy available to repair and adapt properly.

Common signs include:

  • Ongoing muscle soreness

  • Struggling to back up sessions

  • Feeling drained after training

  • Reduced training capacity

Recovery requires adequate fuel availability — especially carbohydrates and overall energy intake.

3. Recurring Injuries and Niggles

Frequent injuries are a major red flag for Underfuelling in Athletes.

The IOC Position Statement on RED-S highlights increased injury risk associated with Low Energy Availability, particularly relating to bone health.

Common examples include:

  • Bone stress injuries

  • Shin splints

  • Tendon pain

  • Muscle strains

  • Persistent niggles

If your body is constantly breaking down, it may not have the energy required to recover and rebuild effectively.

4. Waking Hungry Overnight

Waking up hungry at 2am or feeling intensely hungry overnight is a surprisingly common sign of RED-S.

This can happen when:

  • Training load is high

  • Carbohydrate intake is too low

  • Overall energy intake is inadequate

Your body may literally be running out of available energy overnight.

5. Missing Periods or Hormonal Changes

For female athletes, missing periods is never something to ignore.

Hormonal disruption is one of the clearest physiological signs of Low Energy Availability.

Changes may include:

  • Missing periods

  • Irregular cycles

  • Lighter periods

  • Worsening PMS

  • Loss of ovulation

Menstrual dysfunction is not a normal consequence of hard training.

Male athletes may also experience hormonal disruption, including reduced testosterone levels, reduced libido, and low energy.

6. Food Obsession and Constant Thoughts About Food

Many athletes experiencing RED-S become increasingly preoccupied with food.

This may include:

  • Thinking about food constantly

  • Intense cravings

  • Anxiety around eating

  • Feeling out of control around food

This is often a biological response to chronic underfueling — not a lack of willpower.

6. Feeling cold all the time

Feeling unusually cold is another overlooked Sign of RED-S.

You may notice:

  • Cold hands and feet

  • Needing extra Layers

  • Feeling cold when others feel fine

When energy intake is too low, the body often adapts by slowing metabolism and conserving energy.

Why RED-S is Often Missed

One of the biggest challenges with RED-S is that athletes may still appear “healthy” externally.

Some athletes are:

  • Still performing well

  • Maintaining their weight

  • Praised for being lean or disciplined

But internally, the body may already be struggling with the effects of chronic Low Energy Availability.

Getting Support Early Matters

One of the biggest mistakes athletes make is waiting until symptoms become severe before seeking help.

RED-S is not something athletes should simply “push through.” Chronic Low Energy Availability can affect:

  • Bone Health

  • Hormones

  • Recovery

  • Mental Health

  • Immune Function

  • Performance

  • Long-Term Health Outcomes

Because RED-S affects multiple body systems, a multidisciplinary approach is often imperative for effective recovery and long-term performance support.

Depending on the presentation, treatment and support may involve:

  • A Sports Dietitian to improve Energy Availability and optimise nutrition intake

  • A Sports Physician and/or an Endocrinologist to assess hormonal, metabolic, cardiovascular, and bone health complications

  • A Psychologist or Mental Health Professional if food anxiety, disordered eating, or body image concerns are present

  • Physiotherapists and Allied Health Professionals to support injury management and return to training

Early intervention can significantly improve:

  • Energy Levels

  • Recovery

  • Hormonal Health

  • Injury Risk

  • Bone Health

  • Relationship With Food

  • Athletic Performance

Seeking support early is not a sign of weakness — it is an important part of protecting both health and performance longevity.

Final Thoughts

RED-S is not just about elite athletes or diagnosed eating disorders.

It can happen to athletes who are:

  • Trying to eat “healthy”

  • Training hard

  • Busy and underprepared

  • Chasing performance goals

  • Accidentally underfuelling for their needs

Your body communicates when it does not have enough fuel — through fatigue, hunger, injuries, hormonal changes, poor recovery, and mood changes.

Recognising the early Signs of RED-S is the first step toward protecting both performance and long-term health.

Mountjoy M, Ackerman KE, Bailey DM, et al. IOC consensus statement on Relative Energy Deficiency in Sport (RED-S): 2023 update. British Journal of Sports Medicine. 2023;57(17):1073-1098. doi:10.1136/bjsports-2023-106994

Ashleigh Brunner
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