Nutrition, Energy Balance and RED‑S: What Active Women (and Men) Need to Know
These days, nutritional information online is everywhere — and very mixed in quality. While there’s more guidance than ever around female health and diet, there’s also an increasing recognition of a condition that many people don’t realise can affect recreational exercisers as well as elite athletes: Relative Energy Deficiency in Sport (RED‑S).
Originally identified in elite athletes, RED‑S is now being reported more frequently in amateur runners, long‑distance exercisers and high‑training individuals — particularly women. According to coverage in the BBC earlier this month, this condition is becoming more prevalent outside elite sport, as more people push training without adequately balancing their nutrition. (Note: story referenced from BBC, 2nd January 2026.)
What is RED‑S?
At its core, RED‑S happens when your energy intake (food/calories) doesn’t match the energy your body spends — not just in exercise, but in basic bodily functions too. When you train hard but don’t eat enough to support that level of activity, your body enters a state of low energy availability (LEA). Over weeks or months, LEA can lead to RED‑S. Healthline+1
This doesn’t only happen because of intentional dieting. It can be:
- Unintentional, when training increases without corresponding increases in food intake.
- Due to under‑fueling because of misconceptions about bodyweight, calories, or “leaner is better.”
- A result of inadequate nutrition timing around training. hatchathletic.com
How RED‑S Affects Your Body
RED‑S isn’t “just tiredness” — it affects many systems in the body. Symptoms and possible consequences include:
- Fatigue, brain fog and poor recovery
- Disrupted menstrual cycles or reduced hormone function
- Increased injury risk and poor bone health
- Lowered immunity and frequent sickness
- Mood changes, depression or anxiety
…among others. Sport Wales+1
Because these symptoms vary so widely, many people don’t recognise RED‑S until health effects become more serious.
Why Nutrition Matters: Fuel First, Then Performance
Unlike quick‑fix diet trends, good nutrition for active people isn’t about eating less — it’s about eating enough and eating well.
Here’s what smart fuelling looks like:
🌿 Balance your macros — carbohydrates to fuel training, protein for repair, healthy fats for hormones.
🍎 Eat frequently enough — long gaps between meals can leave your body in deficit.
🏃♀️ Refuel after exercise — the body needs energy to recover and adapt.
💧 Hydrate well — dehydration increases stress on the body and can exacerbate fatigue.
Making sure your calorie intake is sufficient for how much you’re exercising is the first step in avoiding RED‑S — and one of the most powerful tools you have for supporting long‑term health and performance. Healthline
Final Thoughts: Listen to Your Body
If you’re training a lot and noticing persistent tiredness, mood shifts, irregular menstrual cycles, slower progress or recurrent niggles, it’s not “just part of training” — it could be your body telling you it needs more fuel and better nutrition. Paying attention early makes all the difference.
And as with any health concern, if you suspect RED‑S or low energy availability, a qualified health professional — ideally sports‑specific — can help you adjust your nutrition and training safely.
For a convenient, wholefood-based post‑workout option, I recommend Purition protein powder – ideal for real-food fuel that supports recovery and hormone health.
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Your Takeaway?
You don’t need a new diet. You need to listen to your body, fuel it well, and train in a way that supports long-term energy and health. Nutrition is part of your foundation — get that right, and everything else gets easier.
Want more support to listen to your body and how to fuel it well? Let me show you how to eat well and support your body for all your energy, nutritional and hormonal needs. Book an appointment here: Honest Body Programmes