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REDs in combat sports: the diagnosis nobody makes
Every symptom looks like a hard camp. Tired, light, cold, irritable, sleeping badly, cycle gone. In most sports that list would prompt a conversation. In this one it is the description of week six.
Which is why it goes unrecognised in weight-class sport for years at a time, and why the answer is a number rather than a feeling.
What it is
Relative Energy Deficiency in Sport describes what happens when energy intake does not cover the cost of training plus the cost of being alive. The body responds by reducing what it spends on functions it can survive without in the short term, which is a different thing from choosing to lose fat.
The cycle stops working as a signal during the menopausal transition, which is a problem specific to competitors in their forties: female athletes over 40.
One period of a career sits outside all of this, with its own physiology and its own return: coming back after a baby.
The older framing was the Female Athlete Triad: low energy availability, menstrual dysfunction, impaired bone health. REDs covers the same territory and extends it, because the consequences reach further than three systems.
| What gets reduced | How it shows up in a gym |
|---|---|
| Resting metabolic rate | Weight stops moving on the same intake |
| Reproductive function | Cycle becomes late, light or absent |
| Thyroid hormones | Cold, flat, slow to warm up |
| Bone metabolism | Nothing, until a stress fracture |
| Immune function | Illness that keeps interrupting camps |
The number underneath all of it
Energy availability. Intake minus the energy cost of training, divided by fat-free mass.
| Energy availability | Classification |
|---|---|
| 45 kcal per kg fat-free mass per day and above | No risk on this measure |
| 30 to 45 | Moderate risk |
| Below 30 | Low energy availability |
Those thresholds were established in female athletes and are applied to men for want of male-specific values. The free calculator gives you your own figure in about a minute, and it is the difference between suspecting something and knowing it.
What the 2023 consensus changed
The framework on this page was updated in 2023, and two of the changes matter enough to state plainly.
The International Olympic Committee consensus statement drew on more than 170 studies published since the previous version, covering roughly 23,800 participants, around 80 percent of them women.
The name changed. RED-S became REDs. You will see both, the older form is still what most people search for, and they refer to the same syndrome.
And the important one: not all low energy availability is the same. The consensus separates two states that used to be discussed as one.
| Adaptable LEA | Problematic LEA |
|---|---|
| Short-term, reversible, sometimes part of a deliberate plan | Prolonged or severe |
| Does not produce the syndrome | Produces disturbances to health and performance |
That distinction changes how a fighter should read everything above. A planned descent is not automatically damaging. The syndrome comes from the depth and the duration, not from the fact of a deficit existing.
Which is exactly what the measurements in a male combat athlete showed: 7 weeks at a moderate deficit produced no disturbance, and 5 days at a severe one did.
The consensus provides the framework and that case study puts numbers in it.
The 2023 statement introduced a clinical assessment tool using a four-colour system, green through yellow and orange to red, with recommendations attached to each level about training and competing.
It is a clinical instrument rather than a self-test, and that is the point. If the earlier sections on this page describe somebody you know, the tool exists so that a doctor can place them on a scale rather than guess.
The consensus also widened the scope in ways worth knowing: more attention to male athletes, to para-athletes, to mental health, and to low carbohydrate availability as distinct from low energy availability generally. And it added guidance on measuring body composition safely, because the measurement itself can provoke the problem it is meant to detect.
Why this sport is built to miss it
Three reasons, and none of them is anybody's fault individually.
The symptoms are the job description. Fatigue, weight loss and irritability in a fight camp do not stand out, because they are what a fight camp produces.
In a rowing squad the same picture would be noticed sooner.
Losing weight is the goal, so the mechanism is disguised. An athlete whose weight is falling is doing what she was asked to do. Nobody investigates a successful cut.
And the signal gets dismissed. Reviews note explicitly that menstrual irregularities are often ignored or dismissed within the athletic environment: by coaches, by support staff, and by healthcare professionals. Research has also found that some medical specialities report less knowledge and confidence in managing REDs than others, so a fighter can raise it and still not be heard.
A condition whose main early sign is treated as normal, in a sport where the mechanism that causes it is the objective, told to people who are trained to push through discomfort.
What looks like a diagnostic puzzle is a system that produces missed cases.
What it costs, measured
An elite female muay thai athlete was followed through a 5-week camp.
- Resting metabolic rate fell by 253 kcal a day
- Maximum cycling power output dropped by 27%
- Creatinine and urea rose, and the lipid profile moved unfavourably
- Fat-free mass loss was limited to 0.6 kg
Read the last line alongside the others. The protein side of that camp was handled well, and the diet was careful.
The problem was the size of the task the camp was asked to complete.
And a boxing cohort measured in ordinary training, not fight week, found two thirds below the low energy availability threshold, with intakes short by 29% for energy and 36% for carbohydrate.
The part that is not reversible
Most of the list recovers when energy availability is restored. Metabolic rate comes back. Cycles return. Training quality returns.
Bone is the exception. Oestrogen deficiency associated with menstrual disruption affects bone metabolism directly, and the deficit accumulates silently across years. A woman can spend several seasons with irregular cycles, feel broadly fine, and be building a problem that presents as a stress fracture or does not present until much later.
That is the reason to treat a missed cycle as urgent rather than interesting.
The overlap with disordered eating
Disordered eating appears throughout this literature as a component of the condition itself, well beyond a footnote.
In weight-class sport the line between a professional requirement and a problem is genuinely hard to see from the inside. Weighing food, restricting before a weigh-in and thinking constantly about the scale are all part of the job for 8 weeks.
Then camp ends and, for some people, the thinking does not.
If you are not sure which side of that line you are on, the uncertainty itself is worth a conversation with a physician or a registered dietitian. It costs an appointment.
The alternative has cost people considerably more than that.
The behavioural side, and how to raise a concern with somebody without driving it underground, is covered in when a weight cut stops being a weight cut.
How to catch it early
Calculate energy availability twice per camp. Once at the start, once when volume peaks. That second reading is where the number falls without anybody changing what they eat.
Track the cycle across camps rather than within them. Use it as a warning light, and leave training schedules out of it. Late or absent during a camp is a stop sign.
If the cycle is not readable because of a continuous contraceptive method, replace it deliberately with the calculated number and a repeatable output measure.
Watch whether strength is still moving in week five. It is the earliest performance sign, and it is free.
Test ferritin at the start of camp, because iron deficiency and under-fuelling reinforce each other and look identical from outside.
What it looks like to take this seriously
Not eating more indiscriminately. Building a camp whose energy demand and weight target are compatible with each other in the first place.
Most of the cases I have seen were not caused by an athlete under-eating on purpose. They were caused by a gap to the division limit that was too large, closed by a camp that was too aggressive, with nobody calculating whether the arithmetic worked.
If the arithmetic does not work, the answer is a different starting weight or a different division, and that is a strategic conversation rather than a nutritional one.
Two complete sample documents are free to read before you buy anything.
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Oleksandr Foka is a sports nutritionist with over a decade in professional sport. He wrestled freestyle from the age of 4 until he was 22, competing as a medallist and champion at Ukrainian and international level, and has worked with amateur boxers since 2017, including champions and medallists at world championships. He has worked in world title camps in boxing with Oleksandr Usyk, Oleksandr Gvozdyk, Denys Berinchyk, Vladyslav Sirenko, Murodjon Ahmadaliev, Israil Madrimov, Sergiy Bogachuk, Sabirzhan Akkalykov and Abylaikhan Zhussupov, and with the Kazakhstan national boxing team and with Kazakhstan judo athletes, and currently works on the WTA tour.
The same rationing logic runs outside sport. On a weight-loss injection the energy deficit arrives faster and with no hunger attached to warn you, and the lean tissue cost has now been measured properly.
Oleksandr Foka — sports nutritionist. Questions: fokaoleksandr@gmail.com
Educational content, not medical treatment or diagnosis. For adults 18+. REDs is a clinical condition requiring assessment and management by qualified medical professionals. If you recognise yourself in this article, that is a reason to see a physician rather than to adjust your own intake. If thoughts about food, weight or your body are causing distress, or if eating feels difficult to control in either direction, please speak to a physician or a registered dietitian.