Hello Runner,
Welcome back to your weekly moment of endurance nutrition!
Happy Weekend!
How are you?
I’m doing well!
Apart from a few minor issues, I'm fine.
Unfortunately, during my long training session (18k) last Sunday, I started to feel pain in my adductor/pelvis. I managed to finish the training session, but I was already limping. I continued on Sunday with pain and rested at home.
On Wednesday, I had track training and felt the same pain again, although less intense this time.
Tomorrow is the Mercè race (10k) here in Barcelona, so we'll see how it goes. I hope everything goes well.
In addition, I felt exhausted and sleepy this week. Even so, I continued with work, studies, and my routine.
Using the low energy I experienced this week as a hook, I bring up the topic of the invisible risk of “chronically low energy” in frequent runners today.
In my case, it was an unusual week and acute fatigue, but chronic low energy can happen to runners and is quite common. Not only in women, but in men as well.
For many runners, the problem isn’t training too much — it’s eating too little. Especially those who train frequently, unknowingly slip into a state of low energy availability. When this happens over time, the body develops something called RED-S (Relative Energy Deficiency in Sport).
And RED-S doesn’t just chip away at your performance — it quietly disrupts your hormones, weakens your immune system, and can put your long-term health at risk.
It may seem like an exaggeration, but this is a condition that happens a lot. I have treated clients in this situation, and I have been in contact with runners who have suffered from it and had to stop training to recover.
The good news is that it can be prevented and recovered from (if you reach that state of REDs). With the right nutrition strategies, you can restore balance, recover faster, and run stronger than ever.
What is RED-S?
Relative Energy Deficiency in Sport (RED-S) happens when your energy intake (food) doesn’t match your energy output (training + daily life).
Think of it this way: you’re not just fueling your runs — you’re also fueling your brain, hormones, immune system, and body in general. If you consistently burn more than you consume, the body starts cutting corners, shutting down “non-essential” functions to conserve energy.
The Risks of Energy Deficit Over Time
When under-fueling becomes chronic, runners may experience:
Persistent fatigue and stalled progress.
Increased risk of stress fractures and overuse injuries.
Disrupted hormones (low testosterone in men, irregular or absent cycles in women).
Slowed metabolism and low thyroid function.
Weak immunity → frequent illness, colds, or infections.
Mental burnout, irritability, and poor sleep.
and more.
How RED-S Affects Hormones & Immunity
Low energy triggers a chain reaction:
Cortisol (the stress hormone) rises, increasing inflammation.
Sex hormones (estrogen, progesterone, testosterone) decline → poor bone health, reduced recovery, lower muscle strength.
Thyroid hormones slow → fatigue, brain fog, lower metabolism.
Immune cells regenerate less efficiently → more sickness, slower healing.
In other words, RED-S forces your body into survival mode — and your performance suffers as a result.
RECOMMENDATIONS
Why Nutrition Matters for Runners
Fueling properly is about more than calories — it’s about giving your body the tools it needs to train, recover, and thrive.
Adequate carbs = energy for endurance and speed.
Protein = muscle repair and recovery.
Healthy fats = hormone production and joint health.
Micronutrients = immune strength and energy metabolism.
When you eat enough and eat smart, you’re not just avoiding RED-S — you’re unlocking better training, faster recovery, and stronger performance.
→ Runners should follow a balanced diet daily. This will ensure improved performance in races and competitions.
In my clinical practice—treating runners who have had REDs—I can say that the vast majority had a very “clean” diet that did not provide the calories they should have been consuming, and many were afraid to eat carbohydrates.
Even when talking to runners (and friends), most are still afraid or avoid eating the necessary amount of carbs they should.
It turns out that runners burn more calories than people who don't exercise and, consequently, need a greater energy and nutrient intake.
Practical Nutrition Tips to Avoid RED-S
Fuel your training: ~ 3–7g of carbs per kg of body weight daily (adjust for training load). The daily amount of carbs will depend on the intensity and duration of the exercise.
Don’t skip recovery meals: Eat carbs + protein within 2 hours after running.
Aim for protein consistently: ~ 20–25g per meal, spread across the day.
Include healthy fats: avocado, olive oil, nuts, fatty fish → vital for hormones.
Stay hydrated: even mild dehydration worsens fatigue.
Watch for red flags: poor recovery, frequent illness, or lack of progress may signal under-fueling.
Personalize your plan: every runner’s needs are different — one size doesn’t fit all.
Of all the tips above, are there any that you don't follow yet? If so, hit reply and tell me your #1 nutrition challenge — I’ll share a recommendation you can use right away.
Want to make sure your nutrition is supporting your running? Book a free call and let’s build your personalized fueling plan.
Track of the week 🎧️
This week's Track of the Week it's an exciting indie rock music for running in zone 4.
I've chosen the track Nightclub by The Vaccines
Any questions or something you would like to share, drop me an email
Wishing you a great weekend and week ahead!
Here’s to health and good runs⚡️
Ana Paula Alonso