Sports Physiotherapist Ascot Vale | What is (RED-S) Relative Energy Deficiency

An Energy Deficit That Most Athletes Never See Coming

Relative Energy Deficiency in Sport, commonly known as RED-S, is a condition that occurs when an athlete’s energy intake consistently falls short of what the body needs to support both the demands of training and the essential functions of daily physiology, including hormone regulation, immune response, bone maintenance, and cardiovascular health. Despite how broadly it affects the athletic population, RED-S remains widely unrecognised, largely because its early signs closely resemble the ordinary fatigue and stress that athletes routinely push through. It can develop without any deliberate restriction of food and can affect athletes of all ages, genders, and training levels. A Sports Physiotherapist Ascot Vale at ALPHA Sports Medicine has published a comprehensive clinical guide to RED-S, drawing on both professional assessment experience and firsthand personal recovery. The guide equips athletes and coaches with the knowledge to identify symptoms early, understand the full scope of health consequences, and take meaningful, practical steps before the condition compounds.

When the Expert Misses the Signs

I have had RED-S twice. The first time at fifteen, the second at twenty-eight. The second time, I was a practising sports physiotherapist. I had studied it, I had assessed patients for it, and I still didn’t recognise it happening in my own body until I had a stress fracture in my foot.

That’s the thing about relative energy deficiency in sport. It isn’t obscure or rare. The warning signs are genuinely easy to miss because there’s almost always a more comfortable explanation sitting right next to the real one.

What Is RED-S?

RED-S stands for relative energy deficiency in sport. It occurs when an athlete’s energy intake, from food, consistently falls short of what the body needs to cover both the demands of training and normal daily function. That daily function includes hormone production, immune activity, bone maintenance, cardiovascular regulation, and basic organ operation. 

The word “relative” is important. RED-S isn’t only about eating too little in absolute terms. It’s about the gap between energy in and energy out, and that gap doesn’t need to be large or deliberate to cause damage. Sustained over weeks or months, even a modest deficit pushes the body into a kind of power-save mode. Non-essential systems get dialled down to protect the critical ones. The result is a cascade of health effects and a gradual but measurable drop in performance.

RED-S vs the Female Athlete Triad

If you’ve come across the term “female athlete triad,” the two concepts are closely connected. The triad, a term established in clinical use through the 1990s, describes three specific conditions in female athletes: disordered eating, loss of menstrual function, and low bone density.

RED-S is the updated model. It includes male athletes, and it recognises a much broader range of health consequences beyond those three, covering metabolic function, gastrointestinal health, cardiovascular changes, mood and cognition, and more.

Both terms are still in use. Many athletes and coaches still search for “female athlete triad,” and a lot of the current clinical guidance sits under the RED-S umbrella. If you’ve arrived here from a search on the triad, most of what follows applies directly.

RED-S Symptoms: The Warning Signs Athletes Ignore

The difficulty with RED-S is that its early signals are almost designed to look like something else.

The subtle signs

The first symptoms I noticed in myself were a lower resting heart rate than usual, broken sleep on nights after I’d trained, and a heaviness in my legs that lingered two or three days after sessions that shouldn’t have been hard. None of those things, on their own, rings alarm bells. Taken together with a stressful period in my life, they made complete sense as stress symptoms rather than RED-S symptoms. That was the wrong interpretation, but it was a convincing one.

Other early warning signs include:

• Delayed recovery after training that isn’t explained by your training load
• Persistent fatigue even on rest days
• Getting sick more often, or colds that take twice as long to clear
• Digestive discomfort that doesn’t have an obvious cause
• Low iron levels on blood work, particularly in female athletes

Symptoms across the body

As RED-S progresses, the effects reach more systems: 

• Hormonal and reproductive: In female athletes, irregular or absent periods are one of the most identifiable signs. These are not normal side effects of heavy training. They indicate that the body has deprioritised reproductive function due to insufficient energy. Female athletes on the oral contraceptive pill lose this signal entirely because the medication regulates the cycle artificially. That’s exactly what happened to me the second time.

In male athletes, RED-S shows up through testosterone changes: reduced morning erections, changes in libido, and slower beard growth. These signals are less well-known and rarely discussed in male athletic settings, which means they get missed far more often.

• Bone health: Stress fractures, recurring soft tissue injuries, and an injury pattern that doesn’t respond predictably to treatment.
• Performance and function: Reduced strength, power and endurance despite a consistent training schedule. Poor concentration. Reduced coordination. Mood swings and irritability that feel disproportionate to what’s happening. A preoccupation with food, weight, or body composition that becomes harder to turn off.

Why Athletes Miss RED-S, Even When They Know Better

My first episode started when I was fifteen. Missing periods for months was the clearest sign, but nobody flagged it, including me. I didn’t restrict deliberately. The mismatch was accidental, the result of high training volume outpacing what I was taking in. The first consequence was shin splints. The second was a lower-limb stress fracture that kept me out of sport for months.

The second episode came at twenty-eight. I picked up a blood infection after a triathlon, and the illness killed my appetite. I was weak, I knew I was under-fuelled, and I kept training anyway because I had a 10km race on the calendar and was going through a relationship breakdown. Training was the thing helping me cope. I ran the race. A few days later, a deep, sharp pain developed in my foot. A scan confirmed a stress fracture.
I had all the clinical knowledge and none of the objectivity. The psychological context around training can make it very hard to hear what your body is actually saying.

RED-S and Stress Fractures: Why Your Bones Pay the Price

Bone is living tissue. It responds to load by remodelling, breaking down slightly, and rebuilding stronger. That process depends on adequate energy, calcium, and hormonal function, particularly oestrogen in female athletes and testosterone in males. When energy availability is chronically low, the body deprioritises bone remodelling, density drops, and bones become less able to absorb repetitive training load. A stress fracture without a clear spike in training volume should prompt a thorough RED-S assessment. Simply offloading the bone won’t address the underlying cause if the energy deficit is still present. The fracture will heal, but bone density won’t rebuild, and the next training block carries the same risk.
 

How to Reduce Your Risk of RED-S

1. Fuel for what you’re actually doing

Your body uses energy to keep you alive at rest, and training adds substantially to that demand. Post-exercise appetite suppression is a real physiological effect. You finish a two-hour ride, eat a normal meal, and think you’ve covered it. You probably haven’t.

For sessions over an hour, take on carbohydrates during the session, not just before or after. Have protein and carbohydrate available immediately after training. If tracking feels useful rather than obsessive, apps like MyFitnessPal or Fuelin can help you see where the gaps are. The goal is a rough picture, not a perfect accounting of every gram.

2. Stop sorting food into categories

Labelling foods as “bad” creates restriction patterns that make under-fuelling far more likely. For an athlete, caloric adequacy matters more than food purity. A burger contains protein, carbohydrates, dairy, and often vegetables. The athlete who avoids it and finishes the week under-fuelled carries far greater risk than the one who ate it and met their energy needs.

3. Pay attention to your mindset

The psychological dimension of RED-S is real and often goes unaddressed. As a teenage athlete, I compared my body to those around me without deliberately restricting, but the habit of comparison was doing something. Even now, I notice the tension between knowing I perform better at one fuelling level and feeling better aesthetically at another. The thoughts still come. Having the language to name them makes them easier to work with. If these patterns are persistent or escalating, seeing a psychologist with experience in athlete health is a practical and worthwhile step.

4. Reframe the goal

Performance is a more useful north star than appearance. I run faster and further now than ever before, and it correlates directly with eating more, not less. My body looks different to when I was under-fuelled, and that no longer concerns me. That shift in focus doesn’t happen overnight, but it is a far more accurate picture of what a properly fuelled body is capable of.

5. Modify training during recovery, don’t just stop

Complete rest is sometimes medically necessary with RED-S, but for many athletes, it carries its own psychological cost. Training is tied to identity, routine, and mental health, and removing it entirely can make recovery harder. When managing my own foot stress fracture, I switched to slower swimming, swapped running for Pilates, and attended run club on a bike. None was a perfect substitute, but they kept me stable while the bone healed.

What’s appropriate depends on the severity of the RED-S and the nature of any associated injury. A sports physiotherapist can help you find the boundary between activity that supports recovery and activity that hinders it.

Can Men Get RED-S?

Yes. The clinical focus on women has created a misleading impression that it is female-specific. Male athletes in weight-sensitive sports such as cycling, rowing, and distance running carry a significant risk. Rather than menstrual disruption, males may notice testosterone-related changes, including reduced libido and persistent fatigue. Recurring injuries and declining performance are shared across both sexes.

When to See a Sports Physiotherapist for RED-S

A sports physiotherapist is often the right first contact when RED-S has led to injury or when you want to stay active through recovery. At ALPHA Sports Medicine across Newport, Ascot Vale, and Bacchus Marsh, we assess RED-S presentations, manage bone stress injuries, and build modified training plans in coordination with other clinicians, because RED-S rarely resolves with a single-discipline approach.

Other team members who play a role:

• GP: Blood testing for hormonal health, iron levels, bone density markers, and general health status. This is usually where the investigation starts.
• Sports dietitian: A fuelling plan built around your actual training demands, not generic calorie targets. This is where the energy mismatch gets addressed practically.
• Psychologist or mental health professional: Especially relevant where body image concerns, disordered eating patterns, or exercise dependence are part of the picture. These factors increase RED-S risk and don’t resolve without direct attention.

If you’re recognising symptoms in yourself, or in someone you train alongside, getting an assessment is a reasonable and proportionate response.

Frequently Asked Questions About RED-S

Final Thoughts

RED-S goes unrecognised because its warning signs are easy to rationalise. Missed periods are “just training.” Fatigue is “just life.” A stress fracture is “just bad luck.” This is how athletes spend months in a deficit that quietly compounds. You don’t need to be restricting deliberately or training at elite volume for it to happen. If your recovery isn’t tracking or your body keeps sending signals you’re explaining away, it’s worth taking seriously. ALPHA Sports Medicine in Newport, Ascot Vale, and Bacchus Marsh works with athletes at every level, in clinic and online.

Your Next Step Starts With ALPHA

Ascot Vale is a lively inner Melbourne suburb known for its parks and active community. ALPHA Sports Medicine offers Physiotherapy in Ascot Vale and its surrounding suburbs.

If your recovery, energy, or performance feels consistently off and the usual explanations no longer add up, it may be time to look at the full picture. As a trusted Sports Physio Ascot Vale provider, ALPHA Sports Medicine supports athletes navigating RED-S through thorough assessments, modified training guidance, and coordinated care across Ascot Vale, Newport, and Bacchus Marsh, with appointments available in clinic and online. Reach out to ALPHA Sports Medicine today to find out more about What Is RED-S? A Sports Physiotherapist’s Guide to Relative Energy Deficiency in Sport.

Contact Information:

Alpha Sports Medicine – Ascot Vale

246A Union Rd
Ascot Vale, VIC 3032
Australia

Ashton Wilson
https://alphasportsmed.com.au/