Relative Energy Deficiency in Sport, Symptoms and Causes Beyond Athletes
- Jul 2
- 4 min read
AnneMarie Smellie is a UK-based neurodevelopmental practitioner, kinesiologist, and hypnotherapist with over 20 years’ experience helping children and adults build resilience, regulate anxiety, and strengthen brain-body foundations for learning and life.
As practitioners, we never stop learning. Recently, I attended a kinesiology conference where I was introduced to a condition I had never previously encountered: Relative Energy Deficiency in Sport, or RED-S. I was genuinely surprised. Having worked with clients for many years who present with chronic fatigue, poor recovery, hormonal imbalances, digestive issues, anxiety, and unexplained health concerns, I found myself wondering why RED-S is still relatively unknown outside sports medicine. The more I learned, the more I realised that the name itself may be part of the problem.
It isn't just about sport
Although RED-S was first recognised in athletes, it can affect anyone whose body does not have enough energy available to support all its normal physiological functions.
Energy availability simply means the amount of energy left over for the body to carry out essential processes after accounting for physical activity. When energy intake is consistently too low for the body's needs, the body begins to make adaptations in order to survive.
This isn't a sign of weakness. It's an intelligent survival response. The body starts prioritising the systems that are essential for immediate survival while reducing the energy available for processes that can temporarily function at a lower level. Over time, this can influence many different body systems.
The ripple effect throughout the body
Research has shown that RED-S may affect multiple aspects of health, including hormonal balance, bone health, muscle function and recovery, immune function, cardiovascular health, metabolic function, reproductive health, growth and development in adolescents, cognitive performance, and mood and psychological well-being.
Many people assume that someone experiencing RED-S will look obviously underweight. That isn't necessarily the case. Someone may appear perfectly healthy externally while their body is quietly adapting to an ongoing energy deficit.
More common than we might think
While elite athletes are certainly at risk, many others may unknowingly find themselves in a similar situation. Examples include highly active adults who train regularly without increasing their food intake, teenagers involved in multiple sports while going through rapid growth, individuals following highly restrictive diets, and people experiencing chronic stress, where the body's energy requirements may increase.
Those recovering from illness or surgery may also be affected, as can individuals whose digestive or nutritional challenges make it difficult to absorb or utilise nutrients effectively. The important point is that every person's energy needs are different. What is sufficient for one individual may be inadequate for another.
Looking beyond the symptoms
One aspect that particularly resonated with me was how easily RED-S symptoms could be mistaken for unrelated conditions. A person may experience persistent fatigue, poor concentration, brain fog, recurrent illness, frequent injuries, reduced exercise performance, low mood, anxiety, disturbed sleep, and hormonal changes, including irregular menstrual cycles.
Each symptom may be investigated individually, yet the underlying issue of insufficient energy availability may never be considered. As healthcare practitioners, this serves as an important reminder that symptoms rarely exist in isolation.
The importance of looking at the whole picture
As a kinesiologist, my work has always centred around understanding the body as an interconnected system. Rather than focusing on a single symptom, I aim to explore the broader picture. This means asking whether the body is receiving adequate nutrition, whether nutrients are being properly absorbed and utilised, whether chronic stress is increasing physiological demand, whether digestive issues could be affecting nutritional status, and whether recovery is keeping pace with physical and emotional demands.
These questions don't replace conventional medical assessment. Instead, they complement it by encouraging a broader understanding of the factors that may influence well-being. Whether RED-S is ultimately the explanation or not, considering overall energy availability is an important part of supporting long-term health.
Raising awareness
One of the greatest lessons I took away from the conference was the importance of awareness. We often admire people who continually push through exhaustion, train harder, eat less, or keep going despite feeling depleted.
Yet the body has remarkable wisdom. When it doesn't have enough energy, it adapts. Those adaptations may help us survive in the short term, but over time, they can affect health, performance, and quality of life.
RED-S reminds us that health is not simply about exercise, diet, or determination in isolation. It is about ensuring that the body's demands and its available resources remain in balance.
As practitioners, parents, coaches, and individuals, recognising when the body may be running on empty could allow us to intervene much earlier, supporting health before more significant problems develop.
Sometimes, the most valuable discovery isn't finding a new treatment. It is becoming aware of a condition that helps us ask better questions. Because when we ask better questions, we are often one step closer to finding the answers our clients have been searching for.
Read more from AnneMarie Smellie
AnneMarie Smellie, Neurodevelopmental Practitioner, Kinesiologist, and Hypnotherapist
AnneMarie Smellie is a UK-based neurodevelopmental practitioner, kinesiologist, and hypnotherapist with over 20 years of clinical experience. She specialises in anxiety, neurodiversity and learning differences, working at the intersection of brain development, nervous-system regulation and emotional resilience. Through her work at Quester Therapies, AnneMarie helps children and adults uncover and address the root causes behind behavioural, emotional, and cognitive challenges. Her writing focuses on practical, compassionate insights that make complex brain-body concepts accessible and empowering.
Disclaimer:
This article is intended for educational and informational purposes only and should not be taken as medical advice or used to diagnose or treat any health condition. RED-S, Relative Energy Deficiency in Sport, is a recognised medical syndrome that requires appropriate clinical assessment.
If you are experiencing persistent fatigue, recurrent injuries, hormonal changes, poor recovery, changes in menstrual function, or any other ongoing health concerns, it is important to consult your GP or another suitably qualified healthcare professional for assessment and advice.
As a kinesiologist, I believe in working alongside conventional healthcare by supporting individuals in exploring the broader factors that may influence their wellbeing, while encouraging appropriate medical investigation whenever needed.
