RED-S: The Silent Killer of Performance
🚨 TLDR: RED-S in 60 Seconds
- Under fueling + hard training can push the body into shutdown
- Impacts health & performance in men and women
- Practical signs: fatigue, slow recovery, performance drop, more injuries, low libido, mood swings, feeling cold
- Other clues: poor sleep, frequent illness, brain fog, gut issues
- Fix the balance: eat more, fuel around training, reduce volume when needed
- Bone support: vitamin D & calcium required for optimal bone health
- Act early to avoid long term damage
If several signs show up together, that’s a red flag for low energy availability.
Want help fixing it? Book in for a call and let’s sort your fueling out.
Most athletes think the grind is all about pushing harder, training longer, eating “cleaner.” But here’s the reality: if you don’t fuel enough to keep up with all that effort, your body pushes back. Hard. That’s where RED-S (Relative Energy Deficiency in Sport) comes in.
In simple terms, it’s when you’re under-eating compared to how much energy you’re burning. You might not notice it at first, but over time, your body starts shutting down things it considers “non-essential.” Performance. Reproductive hormones. Bone health. The stuff you actually care about.
Why It’s a Problem
RED-S is brutal because it doesn’t just sap performance, it drags your health down too. Your metabolism slows. Hormones get thrown out of whack. For men that usually means low testosterone & libido. For women, missed or irregular periods. Bones become weaker, so injuries pile up. Recovery slows to a crawl. Even your immune system takes a hit, which is why people in this state often catch every cold going around.
For years it was thought of as a problem only for women, mostly framed around the Female Athlete Triad. But now we know men are at risk too. The warning signs just look different.
Who’s at Risk?
Anyone who pushes hard without matching fuel is vulnerable, but some groups get hit more often. Think endurance athletes logging huge hours. Fighters & gymnasts trying to make weight. Physique athletes leaning down. Teens & young adults still growing. Of course, anyone caught in cycles of dieting, fasting, or restricting food is also at risk.
It’s not always about disordered eating either. Sometimes it’s just poor planning, mismanaged programming, not tracking intake, or underestimating what “enough food” actually looks like.
The Red Flags
Here’s where things get sneaky. RED-S doesn’t slap you in the face with one obvious symptom. Instead, it creeps in. You might notice you’re always tired, even after easy sessions. Training that used to feel manageable now leaves you wrecked. Performance drops, injuries creep in, recovery drags out. Libido takes a nosedive. Mood goes sideways. Some people start feeling cold all the time, even indoors.
To make it more practical, here’s a quick checklist of symptoms you can keep an eye on:
Constant fatigue & slow recovery
Training performance dipping even with consistent effort
Recurring injuries, especially stress fractures or tendon issues
Drop in sex drive or libido
Mood swings, irritability or low motivation
Feeling cold more often than normal (hands, feet, indoors)
Trouble sleeping or poor-quality sleep
Frequent illnesses (colds, flu, infections)
Brain fog or difficulty concentrating
Digestive issues like bloating or constipation
Individually, these can be easy to brush off. But if a few show up together, it’s a big warning sign that your body is running on empty.
Turning It Around
The fix is straightforward, even if it isn’t always easy: restore energy balance. That means eating more, training a little less, & actually fueling around sessions. Sometimes that’s as simple as adding a few hundred calories a day or shifting training volume down for a while. Bones need love too, so calcium & vitamin D can help patch some of the damage. If disordered eating or anxiety around food is part of the picture, getting professional support is non-negotiable.
The point isn’t to eat recklessly or stop training. It’s to create enough energy availability for your body to perform & stay healthy. Because if you don’t, your body will make the decision for you, & you won’t like how it feels.
Bottom Line
RED-S is not rare.
It’s the silent killer of progress for anyone pushing hard without proper fuel. Early recognition matters. If you’re noticing fatigue, performance dips, recurring injuries or low libido, don’t wait until it spirals. Eat more. Train smart. Recover properly.
Want help figuring out the right balance for your training & nutrition? That’s quite literally what I do at Roman Nutrition. Let’s make sure you’re fueling for health & performance.