Are You Fuelling Enough for Your Training? Understanding RED-S in Athletes

By Osteopath Carien Boshoff

Hormones influence far more than reproduction. They affect energy levels, recovery, injury risk, and how the

body adapts to training. In this series, we explore how different hormonal stages influence performance and

what athletes can do to support their bodies. One important factor in this conversation is Relative Energy

Deficiency in Sport (RED-S), a condition that can occur when energy intake does not meet the body’s

training and physiological demands. This can occur in BOTH females and males.

Have you ever felt constantly fatigued during training, struggled to recover between sessions, or noticed

recurring injuries that don’t seem to resolve despite doing everything “right”?

Sometimes these challenges are not simply about training harder or pushing through. They may reflect something deeper is happening in the body.

One possible contributor is a condition called Relative Energy Deficiency in Sport (RED-S).

RED-S occurs when the body does not have enough available energy to support both exercise demands

and the essential functions required to maintain health. When this imbalance persists over time, it can

influence multiple systems in the body, including metabolism, hormones, bone health, recovery, and overall

performance.

From an osteopathic perspective, RED-S highlights the importance of viewing the body as an integrated

system. Training load, nutrition, recovery, stress, sleep, and hormonal health all interact to influence

performance and long-term wellbeing.

Understanding Energy Availability

Energy availability refers to the amount of energy left for normal bodily functions after the energy cost of

exercise has been subtracted from dietary intake.

When energy availability becomes too low for a prolonged period, the body begins to prioritise essential

survival processes and downregulates other functions such as reproduction, bone maintenance and

metabolic efficiency.

This state can develop for several reasons:

• High training loads without sufficient nutritional intake

• Intentional or unintentional under-fueling

• Rapid increases in exercise volume or intensity

• Pressure related to body composition or weight-sensitive sports

• Busy schedules that make regular eating difficult

Importantly, RED-S is not always associated with disordered eating. In many cases, athletes simply

underestimate how much energy their training actually requires.

Signs and Symptoms of RED-S

Because RED-S affects multiple body systems, symptoms can appear in different ways. Common indicators

may include:

Performance related changes

• Decreased strength or endurance

• Slower recovery between sessions

• Plateau or decline in performance

• Reduced training tolerance

Hormonal and reproductive changes

• Irregular or missed menstrual cycles

• Reduced libido

• Hormonal disruption affecting metabolism and recovery

Musculoskeletal changes

• Recurrent injuries

• Stress fractures

• Reduced bone density

• Persistent muscle soreness

General health changes

• Ongoing fatigue

• Frequent illness due to reduced immune function

• Mood changes or irritability

• Poor sleep quality

Not every athlete will experience all symptoms, and in some cases, the signs develop gradually over time.

Why RED-S Matters for Musculoskeletal Health

One of the most significant consequences of RED-S is its effect on bone health and tissue repair.

Low energy availability can disrupt hormone production, particularly oestrogen and testosterone, both of

which play an important role in maintaining bone density. Over time, this may increase the risk of bone

stress injuries or fractures.

Muscle recovery and collagen synthesis may also be affected, meaning tendons, ligaments and muscles

may not adapt effectively to training loads.

For osteopaths and other manual therapy practitioners, this can present as recurrent injuries, delayed

healing or persistent musculoskeletal pain despite appropriate treatment and rehabilitation.

Understanding the broader context of energy availability helps ensure that treatment focuses not only on

symptoms, but also on underlying contributors to injury risk.

Training Considerations When RED-S Is Suspected

If RED-S is suspected, the goal is not simply to stop training, but to restore balance between training load,

nutrition, and recovery.

Key considerations may include:

• Reviewing overall training volume and intensity

• Ensuring adequate fueling before and after exercise

• Supporting consistent meal timing throughout the day

• Prioritising sleep and recovery strategies

• Gradually progressing training loads once energy balance improves

Addressing RED-S often requires a collaborative, multidisciplinary approach to ensure both performance

and long-term health are supported.

Why This Matters in Osteopathy

Osteopathy takes a whole-person approach to health and performance. When assessing and managing

athletes, osteopaths may consider factors such as:

• Training load and recovery capacity

• Nutritional status and energy availability

• Sleep quality and stress levels

• Hormonal health and menstrual function

• Injury history and tissue adaptation

Understanding RED-S allows clinicians to better identify patterns that may contribute to recurrent injuries or

stalled rehabilitation, ensuring care addresses both structural and systemic factors.

Important Notes

Not all fatigue or performance decline is related to RED-S. Many factors, including stress, illness, sleep

disruption, or overtraining, can produce similar symptoms. However, persistent fatigue, recurrent injuries or

menstrual disturbances should be discussed with a qualified health professional.

Exercise and nutrition advice should always be individualised based on health history, training goals, and medical guidance. This information is general in nature and not a substitute for personalised medical advice.

The Takeaway

Your body needs enough energy not only to perform but also to maintain health. Fueling appropriately for

your training supports muscle recovery, bone strength, hormonal balance, and long-term performance.

When energy intake does not match training demands, the body may begin to compromise essential

systems. Recognising the signs of RED-S and addressing them early helps athletes maintain sustainable

performance and protect long-term wellbeing.

HOW?

Pay attention to persistent fatigue, recurring injuries, changes in menstrual patterns or declining

performance. These signals may indicate the body needs more support through nutrition, recovery or

training adjustments.

Coming Next

In our next blog, we will explore training considerations during perimenopause, a stage where hormonal

patterns begin to shift, and factors such as recovery, strength development, sleep, and injury risk may

change. Understanding these transitions can help individuals continue training effectively while supporting

long-term health and performance through every stage of life.

References

Elliott-Sale, K. J., Tenforde, A. S., Parziale, A. L., Holtzman, B., & Ackerman, K. E. (2018). Endocrine effects

of relative energy deficiency in sport. International Journal of Sport Nutrition and Exercise Metabolism,

28(4), 335–349. https://doi.org/10.1123/ijsnem.2018-0127

Logue, D., Madigan, S. M., Delahunt, E., Heinen, M., Mc Donnell, S. J., Corish, C. A., & Warrington, G. D.

(2018). Low energy availability in athletes: A review of prevalence, dietary patterns, physiological health,

and sports performance. Sports Medicine, 48(1), 73–96. https://doi.org/10.1007/s40279-017-0790-3

Mountjoy, M., Sundgot-Borgen, J., Burke, L., Ackerman, K. E., Blauwet, C., Constantini, N., Lebrun, C.,

Lundy, B., Melin, A., Meyer, N., Sherman, R., Steffen, K., Budgett, R., & Ljungqvist, A. (2018). IOC consensus

statement on relative energy deficiency in sport (RED-S): 2018 update. British Journal of Sports Medicine,

52(11), 687–697. https://doi.org/10.1136/bjsports-2018-099193