Published on 03 June 2026
If you are active in sport but not consuming sufficient energy through food you may be at risk of RED-S which affects both health and performance. Having low energy availability means your body will not be properly equipped to cope with exercise and normal functions.
What are the symptoms of RED-S?
Symptoms can vary significantly and may include:
- Long-lasting fatigue
- Muscle soreness
- Hormonal imbalances
- Recurrent illnesses – even the common cold
- Bone injuries including stress fractures
- Digestive issues
- Poor sleep
- Night hunger
- Feeling cold persistently
Are there psychological signs as well?
Yes, you may have mood changes with increased irritability, anxiety, and persistent depression. Furthermore, you may experience severe mental tiredness with poor focus and brain fog.
Who can be affected?
It used to be thought that women particularly were susceptible to having RED-S but research has shown that anyone regardless of gender, age, and levels of exercise experienced can have the condition.
What may happen?
You may experience a reduction in overall muscle strength, endurance, co-ordination and performance in your chosen sports activities.
What should you do?
Low energy availability and RED-S can be difficult to identify and often are not diagnosed. If you are concerned, you might want to consider seeing a sports medicine specialist who will look at your overall health and wellbeing.
A DEXA scan may be advised – it is the gold standard method to determine bone mineral density and body composition in athletes suspected of having RED-S. The scan evaluates physiological damage caused by chronic low energy availability.
Looked for are signs of osteopenia and osteoporosis which are key indicators of low bone health.
The scan accurately measures fat mass and muscle tissue and this assists sports dieticians in calculating your resting metabolic rate and how many calories you need to resolve any energy deficit.
For athletes recovering from RED-S, a DEXA scan is typically repeated every six to 12 months so that improvements in bone density and lean mass can be tracked.
Levels of risk
You may be considered to by at high risk of having RED-S if you use extreme techniques to lose weight or have signs of a serious medical condition related to RED-S.
If you have lost a significant amount of weight in the past month, have irregular periods or a history of bone fractures, then you may be at moderate risk.
A person at low risk is an individual who has a healthy physique, does not adopt an unhealthy diet or exercise strategies and is in overall good health.
Avoid fasting
Fasting can increase stress hormone levels and drain energy storage in the body – as a result, it can be more difficult to train well and to recover properly after exercise.
If your body does not have sufficient energy available, even for short periods during the day, then there can be an increased risk of having RED-S.
Don’t trust your appetite
A training session may suppress your appetite so you may have to eat even if you are not hungry. On particularly active days you may need to continue eating even though hunger has been dispelled.
Nutrition guidance
It is not just specific forms of exercise which use energy – your usual activities such as walking the dog, cycling to the office, or being energetic at work all add to your energy needs and should be considered when determining your energy demands.
Eating enough
Typically, women need to eat at least 2,000 kcal per day and men 2,500 kcal a day. If you have RED-S you my need a much greater intake because you are likely to be more active than is usual and need to make up for a lack of calories over time.
A woman weighing 60 kg, having 20% body fat, and participating in exercise which burns 500 kg per day, should be eating at least 3,100 kcal a day to maintain normal function.
Contact us for help with RED-S
If you are concerned about having RED-S then consider booking an appointment with one of our Private GPs or with our registered Nutritional Therapist.
To book, or for more information, complete our online enquiry form, contact us using Livechat or call our Private Patient Team on 01580 363158.