RED-S in Athletics: What Coaches Need to Know About Fuel, Health and Performance
Relative Energy Deficiency in Sport, better known as RED-S, is an important area of athlete health that coaches should understand.
In this presentation, Bryce Anderson and coach Mel Mustapic explore RED-S from both a practitioner and coaching perspective. A key message is that coaches can play an important role in noticing early warning signs, asking thoughtful questions, building a healthier training environment, and guiding athletes towards appropriate professional support.
Bryce brings his experience as a sports dietitian and physiologist, while Mel shares the practical lessons she has learned as a coach supporting athletes through RED-S.
What is RED-S?
At its core, RED-S is an energy problem.
Bryce explains it through the idea of energy availability. The body needs energy not just for training, but for growth, immunity, bone health, recovery, reproductive health, school, work, daily life, and normal body function. When the energy coming in through food does not meet the energy going out through training and life, the body begins to operate with a deficit.
That deficit can happen in two broad ways.
An athlete may simply not be eating enough for their baseline needs. Or, very commonly in athletics, their training load or intensity increases but their food intake does not rise to match it.
This is where low energy availability, or LEA, begins. Bryce uses the analogy of a phone battery. At full charge, the athlete is thriving. They can train, compete, recover, adapt, and function well in life. As the battery drains, the body begins to enter a kind of “battery saver mode”. Initially, this may be low energy availability. Over time, or with greater severity, it can progress to RED-S.
The important distinction is that RED-S is not just “being tired” or “not eating enough”. It is a medical issue that can affect health, performance, hormones, bone mineral density, injury risk, immune function and long term wellbeing. Coaches should not attempt to diagnose it. They should recognise possible signs and refer to qualified professionals.
RED-S Isn’t Just a Distance Running Issue
One of the most important myths addressed in the presentation is that RED-S only affects female distance runners.
It does not.
While endurance athletes may be at higher risk because of the energy demands of their training, Bryce and Mel make it clear that RED-S can affect sprinters, jumpers, throwers, combined event athletes, males, females, juniors, seniors and athletes across body types.
This matters for athletics coaches because the stereotype can make us miss what is right in front of us. A 400 m hurdler, a pole vaulter, a middle distance runner, or a young sprinter completing long training sessions and gym work can all find themselves in an energy deficit.
The same applies to junior athletes who play multiple sports. A coach may only see two athletics sessions a week, but the athlete may also be doing school sport, club sport, gym, refereeing, cross country, or weekend competitions. Every activity adds load. Every load needs fuel.
It’s Often Unintentional
Coaches may hear RED-S and immediately think of eating disorders or deliberate restriction. These can certainly be contributing factors and should be taken seriously. But the presentation makes an important point: many cases are inadvertent.
In other words, the athlete is not necessarily trying to lose weight or restrict food. They simply do not realise how much fuel their body needs.
This is particularly relevant for junior and developing athletes. A young athlete may eat three meals a day and still not be close to meeting their needs. A parent may say, with complete sincerity, “They eat well.” But “eating well” for a growing athlete who trains several times per week is very different to eating well for a non training teenager.
This distinction is crucial. A nutritious diet is not automatically an adequate sports nutrition strategy. Plenty of fruit, vegetables and home cooked meals are valuable, but they may still fall short if the athlete is not eating enough total energy, enough carbohydrate, or enough around training.
As Bryce says in the presentation, the fuelling requirements for athletes can be surprisingly high. That is not poor discipline. That is biology being annoyingly specific.
Performance Can Mask the Problem
One of the most challenging messages for coaches is that RED-S does not always appear as poor performance at first.
Mel describes this as one of the hardest parts to detect. The athlete may be running well. They may be winning medals. They may be qualifying for major competitions. In some cases, performance may even improve for a period.
That improvement can be misleading.
Bryce describes this as “fool’s gold”. The athlete may hold things together for a while, but the underlying systems are under strain. Eventually, the body can reach a tipping point. That may appear as injury, illness, poor recovery, mood changes, menstrual disruption, bone stress, or a sudden inability to back up training.
For coaches, this means we cannot rely only on the stopwatch, tape measure or placing. Performance is one data point. It is not the whole athlete.
A young athlete running personal bests while repeatedly reporting niggles, missing periods, getting sick, struggling with mood, or leaving long gaps without eating should still raise concern.
The Warning Signs Coaches Should Notice
The presentation does not suggest that coaches need to become clinicians. But it does encourage coaches to become better observers.
Possible warning signs include:
Low mood, anxiety, irritability or reduced motivation
Difficulty concentrating
Frequent comments about food, weight, body shape or wanting to be leaner
Fatigue, even when sleep appears adequate
Poor recovery between sessions or competitions
Repeated niggles, joint pain, muscle pain or bone stress injuries
Frequent illness or reduced immune function
Gut issues, especially around hard sessions or competition
Irregular, absent, unusually frequent or otherwise changed menstrual cycles
Low ferritin or repeated iron issues
Inconsistent ability to back up training sessions
A pattern of arriving under fuelled, skipping snacks, or leaving long gaps between meals
The key point is that RED-S is often not one big sign. It is a pattern. One comment about weight may not mean much. One tired session may not mean much. One missed snack may not mean much. But when several small flags appear together, coaches should pay attention.
Mel’s phrase “look for all the flags” is one of the strongest coaching messages in the presentation.
Menstrual Health Should not be Taboo
The presentation is clear that menstrual health can be an important early warning system for female athletes.
For coaches, particularly male coaches or coaches working with younger athletes, this can feel like uncomfortable territory. But discomfort is not a good enough reason to ignore a key health marker.
The goal is not to interrogate athletes. It is to create an environment where athletes understand that menstrual health is a normal part of athlete health, and where they feel safe to raise concerns with the right person.
A practical coaching approach might be:
“Your cycle can be a useful sign of how your body is coping with training, recovery and fuelling. You do not need to share personal details with me, but if your cycle becomes irregular, disappears, becomes unusually frequent, or changes significantly, it is worth speaking with a parent, GP, sports doctor or sports dietitian.”
That kind of language keeps the focus on health, gives the athlete agency, and avoids making the coach the medical provider.
Do not Judge RED-S by Appearance
Millie’s story is one of the most important parts of the presentation.
She explains that she never looked like the stereotype people may associate with RED-S. That is exactly why coaches must avoid making assumptions based on body shape.
Mel reinforces this strongly. An athlete can look lean and be healthy. Another athlete can look strong and still be in low energy availability. Another athlete can be injured, under fuelled and not look like anything is wrong.
RED-S is not a look. It is a physiological state.
This matters deeply in athletics because our sport has a history of overvaluing body shape, leanness and “looking fit”. Coaches need to be very careful with language around body composition, uniforms, weight, size and appearance.
Bryce’s advice is clear: coaches do not need to comment on an athlete’s body shape, size, weight, or uniform changes. If body composition is ever relevant, it belongs in the hands of qualified professionals, at the right stage of development, and with athlete health at the centre.
Fuelling Should be Part of Training Culture
One of the strongest practical messages from Mel is that nutrition needs to become part of the squad culture, not an afterthought.
That does not mean coaches should write meal plans. It means coaches should normalise fuelling behaviours.
For example:
Ask athletes if they have eaten before training
Encourage them to bring a recovery snack
Build quick fuelling reminders into session routines
Talk about food as performance support, not weight control
Remind athletes that harder training blocks require more food
Encourage parents to understand that athletic children may need more than siblings or friends
Bring in qualified sports dietitians or nutrition professionals for education sessions
Challenge poor information from social media or “well meaning friends”
The message is not “eat anything, anytime, without thought”. The message is that athletes need enough energy, enough carbohydrate, enough protein, and enough consistency to support the work they are doing.
Carbohydrates Matter
A major theme of the presentation is the importance of carbohydrate availability.
Bryce explains that insufficient carbohydrate intake can contribute to low energy availability. Importantly, even if total calories seem adequate, inadequate carbohydrate can still be a problem for training, recovery, hormones and performance.
This is especially important in athletics, where speed, power, repeated efforts, high intensity work, and competition all rely heavily on carbohydrate availability.
For coaches, this does not mean prescribing exact grams or meal plans. It does mean understanding that carbohydrate is not the enemy. In athletics, it is a major performance fuel.
Practical examples discussed in the presentation include carbohydrate rich options before training, such as bagels, honey, juice, white bread, pikelets, bananas, muesli bars and similar easy to digest foods. For longer sessions, including long sprint and power sessions that may last several hours, athletes may need food during training. After training, Bryce emphasises the value of getting carbohydrate and protein in early, even if dinner is coming later.
This is a useful coaching cue:
“Have you got something packed for after training?”
Not, “Are you eating clean?”
Not, “Are you watching your weight?”
But, “Are you fuelled to adapt?”
Recovery from RED-S Takes Time
Millie’s story also highlights that recovery is not a quick fix.
She describes the social and emotional challenge of needing to eat more at school, having bigger snacks and lunches than her friends, and coping with body changes during recovery. She also describes returning to RED-S after moving into a more intense training environment overseas, where the training intensity increased and she was not fuelling adequately for the demands.
This is a vital lesson for coaches. Recovery is not just a matter of telling an athlete to eat more. It may require medical input, dietetic support, changes to training, family education, psychological support, patience, and ongoing communication.
Bryce explains that RED-S diagnosis and management may involve sports dietitians, sports physicians, blood tests, bone density assessment, resting metabolic rate testing and other investigations. Some athletes may need reduced training load. Others may be able to continue training with increased energy intake and careful monitoring. The decision belongs with qualified professionals.
For coaches, the key role is to support the process and avoid rushing the athlete back before their body is ready.
As Mel notes, RED-S is not a sentence. Athletes can come back stronger, healthier and better informed. But the process needs patience.
You are on the Front Line, But Not Alone
One of the most valuable messages in the presentation is that coaches are often the front line.
Coaches see athletes regularly. They notice when someone is unusually flat. They hear the throwaway comments about weight. They see the athlete who always forgets food. They notice the recurring niggles, the repeated illness, the sudden mood change, or the athlete who can do one great session but cannot back up the next.
That does not mean the coach should become the doctor, dietitian or psychologist.
It means the coach should know what to do next.
A good coach response might include:
Notice the pattern
Start a calm and private conversation
Avoid judgement or body comments
Involve parents or guardians where appropriate, especially with juniors
Refer to a sports dietitian, GP, sports physician or psychologist
Adjust training expectations if advised
Keep communication open
Support the athlete as a person, not just a performer
This is where a coach’s relationship skills matter. Athletes are more likely to share concerns when they feel safe, cared for and heard.
What You Can Do This Week
A coach watching this presentation does not need to rebuild their whole programme overnight. Start small.
Add a simple fuelling prompt before training: “What have you eaten in the last couple of hours?”
Add a recovery prompt after training: “What is your snack before you leave?”
Review your training loads across the whole athlete, not just the sessions you prescribe. Ask about school sport, gym, weekend games, other coaches and extra running.
Stop using body shape or leanness as casual performance language.
Create a simple referral list of trusted professionals: GP, sports doctor, sports dietitian, psychologist, physiotherapist.
For junior athletes, consider a parent education session on fuelling for growth, training and recovery.
For female athletes, normalise menstrual health as part of athlete wellbeing.
For all athletes, make it clear that asking for help is not weakness. It is good performance practice.
Final Message
RED-S is complex, but the first coaching step is simple: pay attention.
Pay attention to the athlete who is always tired.
Pay attention to the one who keeps getting sick.
Pay attention to repeated niggles.
Pay attention to comments about food, weight or body shape.
Pay attention when training load increases.
Pay attention when a junior athlete is juggling multiple sports.
Pay attention when an athlete says they “eat well”, but their day includes long gaps without food.
Most of all, pay attention to the culture you create.
A healthy squad culture does not make athletes fearful of food. It does not praise leanness as a shortcut to performance. It does not treat fuelling as optional. It teaches athletes that training only works when the body has enough energy to adapt.
The coach does not need to have every answer. But the coach does need to notice, care, communicate and connect athletes with the right support.
That may be the difference between an athlete quietly struggling in battery saver mode, and an athlete learning how to thrive.
