The Dangers of Under-Fuelling: Relative Energy Deficiency (RED)

By Antonia Osborne, Registered Sports Nutritionist & Performance Coach, MSc Clinical Nutrition

In a time where weight loss and cutting calories is glorified, and doing more exercise is considered better, there isn’t so much time and attention given to the other side of the equation.

This article explores what can happen to our health and performance when we under fuel and overtrain.

Low energy availability (LEA)

Low energy availability occurs when the calories from your diet are insufficient to support all of your energy expenditures - your health, general activity and any exercise and sport.

As a consequence, you have insufficient energy to meet all the needs of your body: calories are prioritised for what’s urgent versus longer term health. For example, the energy needs for a menstrual function are not considered urgent and therefore may shut down.

This can cause serious and detrimental issues for our health, wellbeing & performance.

When low energy availability lies on the adaptable end of the spectrum, it’s very short term and unlikely to result in health, wellbeing or performance issues.

Energy availability calculation:

Energy availability = (Energy intake (eating) - Exercise energy expenditure) / Fat free mass

If low energy availability lies towards the problematic end of the spectrum, then it's more severe in magnitude, longer term and results in health, wellbeing and performance issues.

What is RED-s?

Relative energy deficiency in sport (RED-S) is a consequence of long term problematic low energy availability, resulting in health and wellbeing issues, as well as decreased sports performance and increased injury risk.

Common features: a slowed metabolism, decreased sex hormone levels, disrupted or no menstrual cycle / reduced morning erections, impaired bone and cardiovascular health and decreased immunity.

More than 25% of athletes in general are at risk for low energy availability and up to 80% athletes in specific sports (athletics, cycling, gymnastics, swimming, rowing, triathlon) are likely to have RED-S.

RED-S was previously named “The Female Athlete Triad” but was renamed to include the multitude of physical and mental issues that occur as well as the fact that males suffer from it.

RED-s vs Overtraining syndrome (OTS) - what’s the difference?

RED-S and OTS share many commonalities - however they have different root causes:

OTS occurs due to inadequate recovery relative to training stress whereas RED-S occurs exclusively due to low energy availability.

There is some overlap - for example with RED-S, performance and recovery will be impaired. And often an athlete fails to increase their calories when they have an increase in training load, causing both overreaching and low energy availability.

Also when you don’t eat enough to support your training, your training stress will increase and your ability to recover will be impaired, driving overreaching which can lead to OTS.

Unlike in OTS, RED-S has a negative impact on bone health - decreasing bone density and increasing risk for bone stress fractures and injuries.

And whilst central nervous system dysfunction is present in both OTS and RED-S, sex hormone dysfunction is prominent in RED-S.

Can RED-S affect males?

Although RED-S is more common in females, it affects males too. It’s most commonly seen in cycling, endurance sports such as running and rowing and weight class sports.

Males levels of sex hormones are impacted (signs such as reduced morning erections) and bone health deteriorates.

For males, in general RED-S occurs at a lower energy deficiency as females are more sensitive to an energy deficiency.

Is RED-s always related to an eating disorder?

Low energy availability and therefore RED-S can occur for both unintentional and intentional reasons.

It can simply be that the person is under-fueling because they don’t understand their needs and/or don’t practically maintain their energy needs.

However, there is also a strong relationship between eating disorders, disordered eating and RED-S.

In this case the person needs to be treated for the eating disorder or be supported with the disordered eating first, in order to address the RED-S.

Tips for preventing RED-s

Follow a personalised diet to meet your energy availability & lifestyle

Proper nutrition is paramount for preventing low energy availability and RED-S - calories, macronutrients, micronutrients and timing. Understanding your specific needs and honouring them is where it is at. Period. This includes what to eat, how much to eat and importantly when to eat - timing is key.

2. Educate yourself

Take the time to understand and appreciate the substantial impact that RED-S can have on health and performance - as an individual, parent or coach. Reading an evidence-based article like this is a great first step, before potentially revisiting the information or discussing it with a registered sports nutritionist/dietician or health practitioner.

3. Create a healthy mindset

How we think and feel about ourselves influences our behaviours. Become aware and honest about any driving factors that could impact your habits around fuelling your body. Through increased awareness, you can then become more intentional about fuelling yourself. A healthy internal dialogue can be helpful, i.e “how can i best fuel and nourish my body to thrive?”

4. Create healthy habits through planning

Whilst mindset is key, practicality is underrated. When you train a lot, or have high calorie needs and lead a full on life, making healthy habits become autopilot is game changing. And this is where planning and prepping is necessary! This means always having your pre and post workout ready to consume immediately at the right times, having meals planned and prepped and snacks easy to access.

5. Monitor and review

Have regular check in points to assess how well you’re adhering to your diet, your training volume and if any stresses are occurring. With this information you can then adapt accordingly.

How to know if you have RED-S

It can be challenging to “know” since signs and symptoms can be subtle and take time to manifest. Some key signs include absent or dysregulated menstrual cycles, bone stress injuries, sudden or significant weight loss, recurrent injuries or illnesses, decreased performance, mood changes and lack of normal growth and development.

If you have any suspicions that you could be suffering from RED-S, regardless of not “knowing”, it’s best to seek support - such as reaching out to a registered sports and exercise nutritionist or dietician or specialist in the area. Early detection is key for helping to mitigate the risk of long term health consequences!

If you think your energy availability may be low…

Seek awareness

Often situations can occur for a long time before we begin to do anything to change them. This is usually down to lack of awareness. The other driving force can be fear. In the case of low energy availability and RED-S, fear of weight gain is common. Once you’re aware of your situation and any feelings, you can then make practical changes based on the objective reality to optimise your health and performance.

2. Increase your energy availability

If you think you could be at any risk of low energy availability and can adequately and safely increase your energy availability with ease, then do so. As well as increasing your overall calorie intake, increasing total carb intake is very helpful since carbs independent of energy availability play a role in levels of sex hormones, thyroid hormones and stress hormones as well as bone remodelling and iron levels. Your overall diet is central to reversing low energy availability and the associated hormonal state - calorie intake, macronutrients, micronutrients and meal/snack timing. Training done in a fed state (so a carb rich pre workout) and immediately refuelling are musts to mitigate a rise in stress hormone levels.

3. Seek support

If you are battling with either of points 1 or 2, or in any way feel that support could help you and your health and performance, reach out to a registered sports nutritionist or dietician. Being supported and guided can facilitate reaching health and performance goals more effectively and help mitigate the risk of further escalation to RED-S signs and symptoms.

Treatment of RED-s

Treatment can often require a multidisciplinary team of health professionals including a Sport & Exercise Physician, a Sports Nutritionist/Dietician, a Sports Psychologist and an Exercise Physiologist. Treatment depends on the person, their situation and addressing their symptoms and root cause. It allways requires increasing energy availability through increasing energy intake and may require reducing energy expenditure too.

Additionally, specific dietary needs must be met, such as having the appropriate amount of certain macronutrients such as carbohydrates and fats for hormonal health, as well as certain nutrients like calcium, iron and vitamin D. Supplementation may also be necessary.

Restoring hormonal health, a clear sign being regular periods, as quickly as possible, is always the goal. This in turn will positively impact other health issues over time - bone health takes a longer period of time to be affected.

Other coexisting conditions such as depression, anxiety and psychological issues will also need to be addressed. So mindset and mental health is key.

Takeaways:

RED-S is caused by problematic low energy availability: when calories in do not meet needs for health, living & exercise.
RED-S results in a multitude of health & performance issues: physical & psychological
RED-S is treated by increasing energy availability: primarily through diet & reducing exercise. Treatment can involve a Sports Nutritionist/Dietician & expert team.

If you think that you could be at risk of low energy availability, reaching out to a registered Sports Nutritionist or Dietician is a great first step to assessing your individual situation and taking the appropriate action to optimise your health and performance - prevention is best!

References

Mountjoy et al. 2023. 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sports (REDs).

Braeden et al. 2022. Low energy availability and Relative Energy Deficiency in Sport: What coaches should know.

Cabre et al. 2022. Relative energy deficiency in sports (REDs): scientific, clinical and practical implications for the female athlete.

Keay 2017. Relative energy deficiency in sports (REDs): practical considerations for endurance athletes.

Keay 2018. Raising awareness of REDs in male and female athletes and dancers.

ABOUT THE AUTHOR:

Antonia Osborne
*Registered Sports Nutritionist & Performance Coach*

Bio:

Antonia’s obsession with health & fitness began back at school with ballet. Her first degree was in Human Biology & Physiology and she then went back to study an MSc in Clinical Nutrition to pursue a career as a Registered Sports Nutritionist & Performance Coach. She now works with athletes, weekend warriors and high performers, coaching them to make sustainable changes with their nutrition, sleep, movement & mindset to feel their best!

Instagram: @antoniaosbornenutrition

Website: antoniaosbornenutrition.com