Bone Health In Athletes – World Osteoporosis Day

For World Osteoporosis Day, we are looking at bone health in athletes.

Athletes often train at high volumes and intensities, which places significant demand on the body. To train well, recover properly and stay healthy, they need enough energy from food to support both performance and normal body function.

When energy intake is too low for the amount of training being completed, it can affect multiple systems in the body, including hormones, immunity, cardiovascular health and bone health. Over time, this can increase the risk of stress fractures, reduced bone mineral density and long-term health issues.

This is where the concept of RED-S becomes important.

What Is RED-S?

RED-S stands for Relative Energy Deficiency in Sport.

It is a condition that can occur when an athlete does not consume enough energy to meet the demands of training, recovery and normal physiological function.

RED-S developed from a previously recognised syndrome called the Female Athlete Triad, which focused on three key areas: low energy availability, menstrual dysfunction and reduced bone mineral density.

We now understand that the effects of low energy availability are much wider than this. RED-S can affect multiple body systems, including:

• Bone health
• Hormonal function
• Menstrual function
• Immune function
• Cardiovascular health
• Psychological wellbeing
• Recovery
• Performance
• Sleep
• Injury risk

We also now know that RED-S does not only affect female athletes. Male athletes can also experience hormonal changes, fatigue, reduced performance and reduced bone density when energy intake is too low.

Why Does RED-S Occur?

RED-S occurs when there is a mismatch between the energy an athlete takes in through food and the energy they use through training, daily activity and normal body processes.

Sometimes this happens intentionally. In certain sports, there may be pressure to maintain a lower body weight or a leaner physique. This can be seen in endurance sports such as cycling or long-distance running, where lower body weight may be perceived to offer a performance advantage. It can also occur in aesthetic or judged sports such as dance, gymnastics or circus performance, where appearance or body shape may be emphasised.

However, RED-S can also happen unintentionally.

An athlete may increase their training load but fail to increase their food intake enough to match it. They may underestimate how much energy they need, struggle to fuel around busy training schedules or avoid certain food groups without replacing the lost energy elsewhere.

In both situations, the body may not have enough energy available to support full health and performance.

How Does RED-S Affect Performance?

Most athletes will recognise the short-term effects of not eating enough. Training may feel harder, recovery may be slower and performance may become inconsistent.

Low energy availability can lead to:

• Fatigue
• Reduced strength
• Reduced endurance
• Poor concentration
• Slower recovery
• Increased injury risk
• Reduced training quality
• Lower mood
• Recurrent illness

This can create a frustrating cycle. The athlete may train harder to make up for reduced performance, but without enough energy, the body cannot adapt properly. Instead of getting fitter, stronger or faster, the athlete may become more tired, more injury-prone and less able to benefit from training.

How Does RED-S Affect Bone Health?

Bone is a living tissue. It is constantly adapting to the load placed upon it. In athletes, this is particularly important because training often places repeated stress through bones, muscles and joints.

When energy availability is too low, the body may start to reduce energy spent on processes it sees as less immediately essential. This can affect hormone production and bone turnover.

Energy deficiency can influence the hypothalamus, pituitary gland, adrenal glands and gonads. This may lead to reduced levels of hormones such as oestrogen and testosterone, both of which are important for maintaining bone mineral density.

Low energy availability may also increase cortisol levels. Cortisol is a stress hormone, and when persistently elevated, it can have a negative effect on bone, immunity and recovery.

Over time, these changes can reduce bone mineral density and increase the risk of bone stress injuries and stress fractures.

Why Is Reduced Bone Mineral Density A Problem?

Our bones are designed to tolerate the stress and strain of daily life and exercise. In athletes, this load can be much higher, especially in sports involving running, jumping, landing or repetitive impact.

If bone mineral density is reduced, the bones may be less able to cope with this repeated load. This increases the risk of stress reactions and stress fractures.

Stress fractures can require a significant period of reduced training or complete offloading to allow healing. This can be extremely frustrating for athletes, as it may mean time away from sport, competition and normal training routines.

In adolescents and young athletes, bone health is particularly important because this is a key period for building peak bone mass. Problems during this stage can have long-term consequences.

Reduced bone mineral density can also increase the risk of osteoporosis later in life. Osteoporotic fractures can significantly affect quality of life, causing pain, reduced mobility and loss of independence.

Why Athletes Should Care About Bone Health

Athletes often focus on performance goals such as speed, strength, endurance or aesthetics. However, bone health is fundamental to all of these.

Strong bones allow athletes to tolerate training, absorb impact, generate force and remain consistent. If bone health is compromised, performance will eventually suffer.

Good bone health requires more than just exercise. It also depends on adequate energy intake, appropriate nutrition, hormonal health, recovery, sleep and well-managed training load.

This is why RED-S is such an important topic. It highlights that performance and health cannot be separated. To train well, athletes need to fuel well.

How Do We Recognise RED-S?

Recognising RED-S can be challenging because symptoms may be subtle and can be mistaken for normal training fatigue.

One clear warning sign in female athletes is menstrual dysfunction, including irregular periods or periods stopping altogether. However, not all signs are this obvious, and in male athletes, RED-S may be harder to spot.

Possible signs and symptoms include:

• Persistent fatigue
• Reduced performance in training or competition
• Recurrent illness
• Recurrent injury
• Previous stress fracture or bone stress injury
• Altered eating habits
• Disordered eating
• Menstrual dysfunction
• Sleep changes
• Increased resting heart rate
• Poor recovery
• Low mood or irritability
• Loss of motivation

If RED-S is suspected, further assessment may include blood tests, ECG and bone density scans, depending on the individual and their symptoms.

A team approach is essential. Athletes may need input from doctors, physiotherapists, dietitians, sports psychologists, coaches and other healthcare professionals.

How Is RED-S Treated?

Treatment for RED-S should involve a multidisciplinary team. This is because RED-S can affect medical health, nutrition, psychology, training, recovery and performance.

The overall aim is to restore healthy energy availability. This usually means ensuring that the athlete is consuming enough energy to support both training and normal body function.

Treatment may involve:

• Reviewing training load
• Increasing energy intake
• Improving fuelling around training
• Addressing disordered eating patterns if present
• Monitoring menstrual or hormonal health
• Managing bone stress injuries
• Supporting psychological wellbeing
• Improving sleep and recovery
• Gradually returning to training where appropriate

Education is a key part of treatment. Athletes need to understand that food is not just fuel for training. It is also essential for hormones, immunity, bone health, mood, recovery and long-term performance.

The concept of “eating to perform” can be helpful. Instead of viewing food as something to restrict, athletes can learn to see it as something that supports strength, resilience, adaptation and athletic potential.

What Can Female Athletes Do?

Female athletes should not ignore changes in their menstrual cycle. Missing periods, irregular cycles or periods stopping altogether can be a sign that the body is under-fuelled or under too much stress.

Female athletes should seek advice if they notice:

• Periods becoming irregular
• Periods stopping
• Recurrent injuries
• Stress fractures
• Persistent fatigue
• Ongoing underperformance
• Concerns around eating or fuelling

It is important to speak to a GP, sports doctor, physiotherapist or dietitian. Reviewing dietary intake alongside training load can help identify whether energy intake is meeting the demands of sport.

What Can Male Athletes Do?

Male athletes can also develop RED-S, even though the signs may be less obvious.

They should not ignore unexplained fatigue, repeated injuries, reduced performance or difficulty recovering from training. Hormonal changes can occur in male athletes with low energy availability, including reduced testosterone levels, which may affect bone density, recovery and performance.

Male athletes should consider seeking advice if they notice:

• Persistent fatigue
• Recurrent injury
• Stress fractures
• Loss of strength or endurance
• Low mood
• Poor recovery
• Reduced libido
• Unexplained performance decline

A sports doctor may consider checking testosterone and other relevant markers if RED-S is suspected.

Nutrition And Training: What Can Athletes Do To Help Themselves?

If you are training regularly, it can be extremely helpful to work with a sports dietitian. They can help you understand how much energy you need and how to fuel around your training.

Useful strategies may include:

• Periodising food intake around training load
• Eating enough before and after training
• Avoiding unnecessary exclusion of food groups
• Tracking food intake and energy expenditure short term if appropriate
• Planning snacks around training sessions
• Prioritising recovery nutrition
• Monitoring changes in performance, mood and fatigue
• Communicating with coaches and healthcare professionals

The goal is not to obsess over food, but to ensure that your body has the resources it needs to train, recover and stay healthy.

Why Early Support Matters

The earlier RED-S is identified, the better.

Addressing low energy availability early can help reduce the risk of stress fractures, hormonal disruption and long-term bone health problems. It can also help athletes return to better training quality and performance.

If you are concerned that you may be at risk of RED-S, or if you are experiencing recurrent injuries, fatigue, menstrual changes or unexplained performance decline, speak to a healthcare professional.

Bone health is not just something to think about later in life. For athletes, it matters now.

Key Takeaways

1. RED-S occurs when energy intake is too low for training demands, affecting health, recovery and performance.
2. RED-S can affect both female and male athletes, with symptoms including fatigue, recurrent injury, reduced performance and hormonal changes.
3. Low energy availability can reduce bone mineral density, increasing the risk of stress fractures and osteoporosis later in life.
4. Early recognition is essential, especially if there are menstrual changes, recurrent injuries, persistent fatigue or unexplained drops in performance.
5. Treatment requires a multidisciplinary approach, including medical, nutritional, psychological and training support.

Conclusion

RED-S is an important issue for athletes because it shows how closely nutrition, training, hormones, bone health and performance are connected. When the body does not have enough energy to meet the demands placed on it, it may begin to compromise essential systems, including those that protect bone health.

Reduced bone mineral density can increase the risk of stress fractures and may have long-term consequences, particularly for young athletes still developing peak bone mass.

The message is simple: athletes need to fuel properly to perform well and stay healthy. If you are training hard, struggling with fatigue, experiencing recurrent injuries or noticing changes in your menstrual cycle or performance, it is important to seek professional advice early.

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Resources

https://bmj.com/content/48/7/491.citation-tools

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