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What is RED S? (Relative Energy Deficiency in Sport)

Over the course of this blog I will try to discuss some of the warning signs of RED-S, what I as a Dietitian would look for and how you could begin to treat it.


What really is RED-S? (Relative Energy Deficiency in Sport)

This is a condition where the body is not provided enough energy for it to perform it's necessary functions. Things like keeping itself warm, making proteins for muscle or keeping bones strong.

You could think of it as a very tired builder with poor building materials trying to build a house. They won't do as good a job as an energetic builder with the best materials and therefore the house will not be as well built or maintained.

This doesn't have to be due to restrictive eating and a relationship with food. It is about energy balance. Matching the energy going in to the energy going out. You could be eating a reasonable amount of food, but you are doing so much activity you could never replace the amount of energy required.

Every part of your body requires energy to maintain it, with the exception of fat stores. As a rule of thumb, every kilogram of non-fat body mass needs 45 Calories a day to survive and be well maintained. But if you are doing a lot of exercise the energy is used for exercise rather than to helping the cells in your body survive.

This can mean cells in your body do not have the energy to perform tasks they are meant to or your body does not have the energy to make the cells needed to do vital jobs around the body.

For example there are cells called Osteoblasts which rebuild bone more strongly. If these are not receiving enough energy they will not do their job and bones will get weaker. Over time you may even end up with fewer Osteoblasts and bones are not maintained as well.

This can result in individuals due to insufficient nutrient intake or due to exceptionally high amounts of exercise. This can also occur in individuals of normal body size and shape.

Women are particularly susceptible to low energy availability (Throughout this blog I'm going to be referring to low energy availability. If there is low energy available to your body you may develop relative energy deficiency in sport (RED-S). low energy availability and relative energy deficiency are not the same thing) as their bodies try to maintain fertility in addition to other body systems. This makes evolutionary sense, there is a better chance of the species survival and of passing on genes if a woman is always ready of bearing a child. However, this means a woman's threshold before body systems begin being shut down is much lower than a mans. Their body will shut down other body systems to prioritise reproduction. If reproductive systems stop it is likely there have been other systems being deprioritised much before.

Your body can cope and adapt to short term low energy states with no ill effect. There is a current craze for fasting and this seems to have beneficial effects to some people despite being in a low energy state for several hours. The risk of complications from low energy availability increases when the duration is longer, low energy states are encountered frequently or the energy deficit is extremely large.

Our bodies are designed to be active, however not designed to be as active as elite training programs demand. Some training programs can take body energy systems to a point where the intestines cannot absorb enough food to meet energy demands. Especially in younger athletes who's intestines are still developing to be capable of absorbing high amounts of nutrition.


What happens in RED-S?

Low energy availability to the body and brain can manifest in different ways depending on the person. Below is a diagram from the International Olympic Committee showing the possible systems affected.

relative energy deficiency in sport RED-S diagram of body systems affected

I won't go through each one in detail. As discussed above, the issues occur because cells no longer have the energy they need to perform their tasks.

The impact on psychological and emotional health is interesting as these, in some cases, can lead to low energy availability. However, low energy availability could also lead to such issues. If the body is feeling exhausted it will try to reduce your energy usage by making you feel emotions which prevent you from being as active.


What I assess as a clinician

  • Training history

  • Diet history

  • Weight history

  • Menstrual history

  • Readiness to train

  • Maybe blood tests

    • female: follicle-stimulating hormone (FSH), luteinising hormone (LH), oestradiol, testosterone, pregnancy test;

    • male: testosterone, LH; and

    • all athletes: full blood count (FBC), thyroid function tests, ferritin, vitamin B12, vitamin D, morning cortisol, prolactin.

Particularly as a dietitian I will conduct a thorough diet history requiring three days of intensively weighing each meal and documenting exact intakes of food. Using this I can analyse and assess intake of not only energy, but all nutrients. Then I can compare this against reported training to assess energy availability and micronutrient deficiencies.

explanation to calculate low energy availability for RE-S assessment

My Experience of low energy availability

I do not believe I have ever experienced RED-S. However, during training camps, when I was an elite rower, I have without a doubt experienced symptoms resulting from low energy availability. Situations where I could not eat enough to meet the energy demands of the training program. This would present as low motivation to train (which would probably lead to poor performance in races also), increased susceptibility to illnesses and injury and finally, and worst of all, I would begin to lose my appetite. Losing your appetite during high training load begins a negative spiral.

preventing relative energy deficiency in sport RED-S by eating processed food

I was fortunate as a heavy weight rower I was always pushed to be as heavy as I could be and therefore motivated to eat as much as I could. I was also fortunate to be given nutritional education from the GB rowing team and have reasonable knowledge myself due to studying Biochemistry. From this education I knew it was okay for me to use processed foods to meet calorie deficits. I would regularly have donuts or cookies or milk shakes. However, I would only have these after my main meals to make sure I was meeting my micronutrient requirements.

There were situations where I refused to train because motivation was low or I felt on the edge of illness or injury. This likely was detrimental for selection with some coaches, but for my health was positive. However, I ignored this attitude from coaches as I believed I knew what was best for myself and my performances. Training does not matter at the end of the day. It is the result in your event which matters.

This highlights the need for a holistic approach to training. Some coaches are led by numbers and ignore how the body feels. There are several good questionnaires to assess readiness to train which could prevent development of RED-S.


What to change if you have RED-S?

Simply put, there needs to be more energy going in and less energy going out.

To achieve this it may be necessary to find the underlying cause. What is the motivator which has lead to this situation? Is it internal or external? Is there a body image pressure where an individual is attempting to make themselves look leaner? Is their sport a weight sensitive sport? Have they been in an exceptionally hard training block?

It may be necessary in the short term to replace micronutrient deficiencies with supplements and use highly processed foods to meet energy demands. Highly processed foods are more easily absorbed by the intestines and can lead to increased energy levels. In longer term this is not a solution due to the lack of micro nutrients in highly processed foods.

This condition is treatable and reversible. But requires changes in behaviour and mindset. Multiple healthcare professionals may be required for diagnosis and treatment.


Thank you for reading my blog. If you have found it useful please click the 'Heart' icon.

You can contact me here for appointment availability and information for other clinicians I partner with to offer appointments.


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