Fuelling Female Athletes: Understanding RED-S

In women’s sport, there’s a big issue that is often hiding in plain sight: under-fuelling. And no, it’s not just about feeling a bit tired. When your body doesn’t get enough energy to keep up with both training and basic functions like hormone production and brain health, things can start to fall apart fast.

This is known as Relative Energy Deficiency in Sport – RED-S.

So, What Is RED-S?

Put simply, RED-S occurs when you’re not eating enough to fuel your body for both sport and everyday functioning. This can be due to an intentional restriction (such as dieting) or an unintentional and subtle restriction – busy schedules, skipping meals or not realising just how much energy your body really needs.

At first glance, RED-S can look similar to an eating disorder — but they are not the same. RED-S is a physical state the body enters when it’s not getting enough fuel to meet the demands of exercise and basic function. Eating disorders, on the other hand, are clinical mental health conditions involving disordered thoughts and behaviours around food, body image, and control.

RED-S can happen unintentionally, especially when someone is unaware they’re under-eating for their training load. In contrast, eating disorders often involve deliberate restriction or compensatory behaviours. Someone with an eating disorder may experience RED-S as part of the physical fallout – but RED-S alone doesn’t always mean there’s an eating disorder behind it.

Who Experiences RED-S?

Whilst anyone can experience RED-S, it often hits female athletes the hardest. Why? Because it doesn’t just mess with your performance, it disrupts periods, hormones, bones, mood and even how your brain works.

The condition was formally recognised by the International Olympic Committee in 2014. It built on the idea of the Female Athlete Triad – a medical model linking low energy, menstrual dysfunction and poor bone health – and highlighted just how many systems can be affected when the body is running on empty.

The Female Athlete Triad: A Quick Breakdown

Before we dive deeper into RED-S, it’s worth understanding the three key areas of the Triad: 

1. Low Energy Availability

   Not eating enough to support training and health. This can be due to dieting, disordered eating or simply not realising how much fuel your body needs to recover and function.

2. Menstrual Dysfunction

   Missing periods (amenorrhea) or irregular cycles happen when the brain suppresses reproductive hormones to conserve energy.

3. Low Bone Density

   Without enough oestrogen or proper nutrition, bones stop rebuilding properly. This can lead to stress fractures or even early onset osteoporosis – especially scary for young athletes.

RED-S: Going Beyond the Triad

RED-S takes the Triad further, showing that low energy can also mess with your heart, gut, immune system and mental health. And yes – it affects men too. But for female athletes, the impact on hormones and the brain is especially important.

The Brain Runs on Fuel Too

It turns out the female brain is extremely sensitive to low energy. In RED-S, levels of the brain chemical BDNF can drop. This protein supports brain flexibility, learning and mood. It can explain why some people experience symptoms like brain fog, irritability and low moods.

Furthermore, oestrogen (specifically a type called oestradiol) which helps with memory, emotional regulation and protecting brain tissue is dramatically lowered in those with RED-S.

This is a major issue, especially for teen and university-age athletes whose brains are still developing.

Hormonal Chaos

Losing your period might seem ‘normal’ in a lot of sport environments, but it’s not. It’s your body waving a big red flag.

When energy is low, your body prioritises survival, meaning reproductive hormones like oestrogen and luteinising hormone get reduced. That means ovulation and periods stop, and fertility takes a back seat.

But it’s not just about periods. Oestrogen is vital for strong bones, heart health and brain function. Long-term hormone disruption can raise your risk of injury and other issues later in life.

Still, many young athletes think no period means peak fitness. That mindset must change.

Why It’s So Common and So Hidden

It’s partly down culture. In endurance and aesthetic sports (think running, dance, gymnastics), athletes are often praised for being ‘lean’ – even if they’re under-fuelled.

Social media doesn’t help either. With performance pressures and body ideals everywhere, it’s easy to slip into harmful habits without even realising it.

A 2022 UK survey of 112 competing female athletes found that 44% of the women were identified as having disordered eating, 53% were at risk of low energy availability and 16% were at high risk of clinical eating disorder.

That’s a huge gap, and it’s starting young with teenage girls not being given the right information about what is going on in their own bodies.

One Model That’s Making a Difference

Thankfully, some institutions are stepping up. The University of Birmingham, alongside BASES (British Association of Sport and Exercise Sciences), have launched a RED-S support programme for student athletes.

Here’s what they’re doing:

• Screening with questionnaires, blood tests and bone scans.

• Tracking menstrual cycles for early warning signs.

• Bringing together sport psychologists, nutritionists and doctors to build a full recovery plan.

Even better than this, they’re training coaches and staff to sport the signs before they become a serious problem.

What Needs to Change?

Awareness of RED-S is growing, but education still lags behind. We need more than leaflets or a one-off nutrition talk. Schools, clubs, and federations must embed RED-S literacy into training and talent development programs.

It’s not just about protecting performance – it’s about long-term health.

Researchers are now asking bigger questions: How does RED-S affect women’s brains years down the line? Could early under-fuelling have a lasting impact on mental health?

Overall, a social push to stop normalising overtraining, under-eating and ‘pushing through’ is needed. In women’s sport particularly, fuelling properly isn’t optional, but rather essential.

References

British Association of Sport and Exercise Sciences (BASES). (2023). RED-S Screening and Prevention Toolkit.

Dipla, K., Kraemer, R. R., Constantini, N. W., & Hackney, A. C. (2020). Relative energy deficiency in sports (RED-S): elucidation of endocrine changes affecting the health of males and females. Hormones, 20(1), 35–47.

Kyniska Advocacy & Project RED‑S. (2023). The Female Athlete Health Report 2023 [PDF]. Kyniska Advocacy.

Mangiarelli Rehabilitation. (2022, October 27). Female athlete triad schematic.

Mountjoy, M., Sundgot-Borgen, J., Burke, L., Carter, S., Constantini, N., Lebrun, C., Meyer, N., Sherman, R., Steffen, K., Budgett, R., & Ljungqvist, A. (2014). The IOC Consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S). British Journal of Sports Medicine, 48(7), 491–497.

Sharps, F. R. J., Wilson, L. J., Graham, C. A. -M., & Curtis, C. (2021). Prevalence of disordered eating, eating disorders and risk of low energy availability in professional, competitive and recreational female athletes based in the United Kingdom. European Journal of Sport Science, 22(9), 1-7.

Subalatha, M., Rachaveti, D., Amutha, S., & Ponpandi, M. (2025). A narrative review on the role of cognition, nutrition and energy availability in athletes of competitive sports to combat RED-S. PeerJ, 13, e18849.