RED-S: When Your Body Starts Shutting Things Down
Most people who come to me with a stress fracture, a hormonal disruption, or a string of injuries that won’t heal aren’t under-training. They’re doing everything they’ve been told is right. They’re consistent, disciplined, pushing through. And their body is quietly falling apart. These are RED-S symptoms – even when they don’t look like it from the outside.
That’s often RED-S. The RED-S symptoms aren’t always obvious – and it’s one of the most commonly missed patterns I see, particularly in people who look, from the outside, like they’re doing everything well.
What RED-S Actually Is
Relative Energy Deficiency in Sport – RED-S – is what happens when the energy going into your body isn’t enough to cover both the demands of training and the demands of keeping everything else running. Your heart. Your hormones. Your bones. Immune function. Your ability to repair tissue after loading it.
When there isn’t enough to go around, the body makes choices. It prioritises what it needs to survive right now, and it quietly scales back everything it considers non-essential. Reproductive function goes early. Bone density follows. Recovery slows. Mood destabilises. And the musculoskeletal system – the bit you’re asking to perform and adapt – starts breaking down faster than it can rebuild.
This isn’t weakness. It’s not a lack of mental toughness or commitment. Your body is doing exactly what it’s designed to do when resources are scarce. It’s trying to keep you alive.
It Isn’t Just an Elite Athlete Problem
RED-S was originally described as the Female Athlete Triad – disordered eating, amenorrhoea, and low bone density – in competitive female athletes. The understanding has expanded significantly since then. It affects men. Recreational athletes too. It affects people who would never describe themselves as athletes at all, but who train regularly and have gradually, often unconsciously, created an energy gap between what they’re burning and what they’re eating.
The energy gap doesn’t have to be dramatic to cause damage. It doesn’t require an eating disorder in the clinical sense. It can come from a busy life where meals get skipped, from a training load that crept up gradually, or from a period of high stress that suppressed appetite. Sometimes it comes from well-intentioned dietary restrictions that made sense on paper but didn’t account for what the body actually needs to repair and function.
The body doesn’t distinguish between intentional restriction and circumstantial under-fuelling. It just notices the gap, and it responds accordingly.
The body doesn’t distinguish between intentional restriction and circumstantial under-fuelling. It just notices the gap.
Why RED-S Symptoms Show Up in the Clinic
People rarely come in saying “I think I have RED-S.” They come in with a stress fracture that isn’t healing on the expected timeline. Or a recurring soft tissue injury that keeps returning despite doing everything right in rehab. Or fatigue that doesn’t make sense given their training load. A hormonal disruption they’ve been told is unrelated to their training.
The connection between those things and energy availability isn’t always obvious, because the symptoms are spread across different areas of the body and often handled by different healthcare professionals who aren’t talking to each other. The GP sees the hormonal picture. The physio sees the injury. Nobody asks about the energy.
That’s where a thorough assessment changes things. Not just looking at where it hurts or what’s structurally compromised, but asking what the body has had to do, what it’s had to work with, and what it’s been prioritising as a result.
RED-S Symptoms: What the Body Is Actually Telling You
One of the things I find most striking about RED-S is how coherent the body’s response is once you understand the logic behind it. Every symptom makes sense. The body isn’t malfunctioning. It’s managing a resource problem with the tools it has.
Low bone density in a young, active person isn’t random bad luck – it’s what happens when low energy availability undermines the hormonal environment needed to maintain bone remodelling. Slow tissue healing isn’t a structural failure – it’s what happens when the raw materials for repair go elsewhere. Persistent fatigue isn’t a mindset issue – it’s a signal that the energy budget is already stretched before training even begins.
The body is always communicating. The question is whether we’re asking the right questions to hear it.
The body isn’t malfunctioning. It’s managing a resource problem with the tools it has.
Common RED-S Symptoms to Watch For
RED-S symptoms span different body systems, which is part of why the pattern gets missed. Here are the signs that most often turn up together:
Signs your body may be under-fuelled
- Stress fractures or bone stress reactions that don’t fit your training load — or low bone density picked up earlier than expected.
- Soft tissue injuries that keep returning despite doing the right rehab.
- Slower than expected healing from injuries that should be progressing.
- Menstrual changes — irregular periods, missed periods, or amenorrhoea (loss of periods entirely).
- Reduced libido or hormonal disruption — in men this often shows up as low testosterone signals.
- Persistent fatigue that doesn’t match your training load.
- Poor sleep despite good sleep hygiene.
- Mood changes — low mood, irritability, or a drop in motivation that wasn’t there before.
- Getting ill more often — frequent infections, slow to recover from colds.
- Performance plateau or regression despite consistent, well-structured training.
Most people don’t have all of these. Two or three appearing together, particularly in someone training regularly, is enough to start asking the energy question.
If parts of this are landing — recurring injuries, missed periods, fatigue that doesn’t match your training — it’s worth talking it through with someone who’ll ask the right questions. The free 15-minute discovery call is exactly that.
Book a Free Discovery CallWhat Actually Needs to Change
The foundation is energy availability – getting enough fuel in to cover both training demands and basic physiological function. That sounds straightforward, but in practice it often requires working with a sports dietitian who understands the specific demands of the training involved, because the numbers matter and generic guidance rarely gets close enough.
From a movement and load perspective, the priority is protecting the tissues that are most at risk while the energy environment improves. That means being honest about training load – not necessarily stopping, but adjusting the demand to match what the body can currently absorb and recover from. Loading bone in the right way is still important; bone responds to mechanical stimulus, and complete rest isn’t always the answer. But the loading has to be appropriate, and it has to be paired with the nutritional support that makes adaptation possible.
There’s also a piece around understanding how the injury or symptom fits into the broader pattern. A stress fracture in someone with RED-S isn’t just a bone problem – it’s a signal about the whole environment the body has been operating in. Treating it in isolation, without addressing the energy piece, is likely to produce another stress fracture somewhere else further down the line.
The Harder Conversation
What makes RED-S genuinely difficult to address is that it often sits inside an identity. Training hard, eating carefully, being disciplined – these are things people are proud of, and rightly so. The idea that those same behaviours might be contributing to the problem can feel confronting, even threatening.
That’s not a reason to avoid the conversation. It’s a reason to have it carefully, with enough context that the person understands what’s actually happening in their body. Not just being given the instruction to eat more and train less. When someone understands the mechanism – when they can see why their body is making the choices it’s making – the response is usually relief rather than resistance. It makes sense of things that didn’t make sense before.
When someone understands the mechanism, the response is usually relief rather than resistance.
That’s what a first session is built around. Not a protocol, but a genuine attempt to understand what’s been happening and why – and to give you a clear picture of what needs to change and in what order.
If This Sounds Familiar
If you’re dealing with an injury that isn’t healing the way it should, recurring problems that keep returning despite doing the right things, or symptoms that don’t quite fit together into a clear picture, it’s worth having a conversation. The free discovery call is exactly that – a conversation, not a commitment. You’ll come away with a clearer sense of what’s going on regardless of what you decide next.
Book a Free Discovery Call at londonosteopath.com/book
Frequently Asked Questions About RED-S
What are the main symptoms of RED-S?
The most common RED-S symptoms are stress fractures or bone stress injuries, recurring soft tissue injuries that won’t fully heal, menstrual irregularities or amenorrhoea, persistent fatigue, mood changes, frequent illness, and unexplained performance plateaus. Most people don’t have all of these — but two or three appearing together in someone who trains regularly is enough to start asking whether under-fuelling is part of the picture.
Can you have RED-S without an eating disorder?
Yes. RED-S doesn’t require disordered eating in the clinical sense. The energy gap can come from a busy life where meals get skipped, a training load that crept up gradually, a period of high stress that suppressed appetite, or well-intentioned dietary restrictions that didn’t account for what the body actually needs. The body responds to the gap regardless of how it got there.
How is RED-S diagnosed?
There’s no single test for RED-S. It’s a clinical picture pieced together from training history, nutritional intake, menstrual function (where relevant), hormonal markers, bone health, and injury patterns. Diagnosis usually involves a sports physician or sports dietitian working alongside other professionals — including osteopaths or physiotherapists who can connect the musculoskeletal symptoms to the broader pattern.
Mountjoy, M., Sundgot-Borgen, J., Burke, L. et al., 2014. The IOC consensus statement: beyond the Female Athlete Triad – Relative Energy Deficiency in Sport (RED-S). British Journal of Sports Medicine, 48(7), pp.491–497. https://doi.org/10.1136/bjsports-2014-093502
Logue, D.M., Madigan, S.M., Melin, A. et al., 2020. Low energy availability in athletes 2020: an updated narrative review of prevalence, risk, within-day energy balance, knowledge, and impact on sports performance. Nutrients, 12(3), p.835. https://doi.org/10.3390/nu12030835
Nattiv, A., Loucks, A.B., Manore, M.M. et al., 2007. American College of Sports Medicine position stand: the female athlete triad. Medicine and Science in Sports and Exercise, 39(10), pp.1867–1882. https://doi.org/10.1249/mss.0b013e318149f111
