Research · Nutrition ·
Under-fuelling and REDs, what the 2023 IOC consensus says
Relative Energy Deficiency in Sport (REDs) is what happens when you don't eat enough to cover both your training and your body's basic needs. The International Olympic Committee (IOC) first described it in 2014. This 2023 update pulls together more than 170 studies published since its 2018 statement.
Ultra runners are a group to watch. Training volumes are high, long days burn a lot of energy, and appetite doesn't always keep up.
What it is
The key idea is low energy availability: the energy left for your body's normal functions after the energy cost of training is taken out. When that stays too low for too long, health and performance suffer. The panel reports estimates of how common REDs is ranging from 15% to 80% of athletes, depending on the sport.
What's new in the 2023 update
- It's a spectrum. The panel separates adaptable low energy availability (short, mild, no lasting harm) from problematic low energy availability (prolonged or severe, which leads to REDs).
- Carbohydrate matters on its own. Low carbohydrate availability adds to the problem, on top of low total energy.
- Mental health and men. Newer research covers links with mental health, and confirms that men are affected as well as women.
- Overtraining overlap. Symptoms overlap with overtraining syndrome, so the panel recommends ruling out low energy and carbohydrate availability first.
- A new screening tool. The REDs Clinical Assessment Tool (version 2) helps clinicians assess severity and risk, with linked training and competition advice.
- Body composition. Guidance on assessing body composition safely, to avoid making the problem worse.
What it means for ultra runners
- Match your eating to your training, especially on big days and big weeks.
- Don't cut carbohydrate hard during heavy training.
- If you're always tired, picking up injuries or illnesses, or your performance is stalling, under-fuelling is worth considering before adding more training or more rest.
- If you're worried, see a doctor or a registered sports dietitian.
Limitations
- This is an expert consensus, which brings together and interprets research. It isn't a single new experiment.
- Measuring energy availability accurately outside a lab is hard.
This is a summary for information only, not medical or dietary advice. Read the original study for full details.