What You Need to Know

RED-S stands for Relative Energy Deficiency in Sport and is exactly what the name implies: a shortage of energy available to keep up with the demands of exercise, on top of essential daily functions (e.g. growth, respiration and digestion).

The term ‘low energy availability’ is used to describe the negative balance (whether intentional or unintentional) between energy intake and expenditure (i.e. food consumed vs physical exertion). In the face of sustained low energy availability, the body goes into 'energy saving mode' which negatively affects almost every system in the body. One concerning effect of RED-S is suppression of the reproductive system (which can result in irregular of missing periods among females), but RED-S can affect any athlete, of any age, gender or level, size or weight and carries serious long-term health and performance implications.

Almost any athlete or exerciser - male or female - whose training demands significant energy output can be at risk of RED-S - from recreational runners to Olympic gymnasts. There is no minimum standard, activity level or years of experience required. One recent study found no difference in the prevalence of restrictive eating, menstrual dysfunction, primary amenorrhea, or injuries between elite and recreational female athletes across a sample set of over 800 athletes.

Athletes from endurance sports or those which promotes a low body weight (e.g. for aesthetics or performance) tend to be at the greatest risk of RED-S for two main reasons.

1) Endurance sports, by nature, demand a lot of energy which can easily be underestimated

2) Where there are pressures to look a certain way or achieve a certain weight, athletes are more likely to manipulate their food intake in order to gain a perceived performance advantage

Certain sports (such as long distance running, climbing, gymnastics, rowing and cycling) involve both a high training load and pressure regarding body composition, making these athletes most susceptible to RED-S.

Causes of RED-S range from unintentional underfuelling (simply misjudging the nutritional requirements of their training/competition load) to a clinical eating disorder. Reasons inbetween can include disordered eating or simply failing to match an increase in training load/intensity with an increase in energy input.

Often, the true cause can be difficult to determine since disordered eating or exercise behaviours are likely to be kept secret and are commonly accompanied by denial. If you, as their coach, are able to confront an athlete early on, it can significantly increase their chances of recovery. Read our tips on how, here.

RED-S is typically diagnosed by a sports specialist via blood tests and an assessment of your relationship with training and nutrition. Unfortunately, many regular doctors won't have heard of RED-S, or will know very little about it if they do.

Whilst every individual is unique, there are a number of common symptoms that you, and they, can look out for. Although many of these symptoms are subtle and therefore difficult to detect, picking up on them early on can significantly help an athlete avoid the long-term consequences of this condition.

Ultimately, determining whether an athlete is experiencing RED-S involves looking at the bigger picture. Their physical and mental health, training and nutrition all need to be considered but there are others tools which can help them and their doctor reach a diagnosis. Other methods of assessing their heath status will involve blood testing for various hormone levels and bone density testing via a DEXA scan (to establish their current bone health status).

We've recommended a few specialists in this field here.

The symptoms of RED-S often overlap with those of the 'Female Athlete Triad', which as the name suggests, focusses only on females and comprises three inter-related parts: insufficient energy intake, amenorrhea (missing periods) and decreased bone density. However, part of the International Olympic Committee's goal in coining the term RED-S was to highlight the fact that low energy availability impacts males as well as females, alongside those who don’t necessarily define themselves as ‘athletes’. And, whilst menstrual function and bone health are often both impacted by low energy availability, the term RED-S describes a far broader range of physiological and psychological consequences across both genders.

As an observer, it can be difficult to distinguish ‘athletic’ from ‘disordered’ eating, but there are a few differences to look out for. Athletic eating is more likely to be directed towards performance improvements, rather than weight loss or altered body composition. There is more emphasis on what needs to be eaten to maintain health and performance, than what is forbidden or unnecessary. Athletic eating habits tend to 'normalise’ in the off-season and in retirement, while disordered eating habits are often maintained or even exacerbated during periods of rest - perhaps for reasons of perceived control or fear surrounding weight gain.

The difference between disordered eating and a clinical eating disorder* (like anorexia or bulimia) surrounds how much the disordered behaviours disrupt someone’s daily life and impair their ability to function. In many cases, disordered eating is a pre-cursor for a clinical eating disorder, but any level of disordered eating can have a significant impact on an athlete's overall health and performance.

It’s important to look hard for the presence of disordered eating behaviours (see below), not simply because they can quickly develop into more serious conditions, but also because they can be difficult to detect – especially among those determined to mask the issue. If you suspect your athlete may exhibit any of the below, try to open up a discussion quickly, directly and confidentially. Find are our tips on how, here.

What does disordered eating look like?

• Sticking to a rigid routine surrounding food and exercise
• Feeling anxious about eating around others or going to new places to eat
• Attaching guilt and/or shame to eating certain foods
• Generally being preoccupied with food, weight and body image in a way that negatively impacts quality of life
• Feeling out of control around food
• Using exercise, food restriction or fasting to ‘make up for’ eating ‘bad’ foods
• Exercising to ‘earn’ food
• Restricting food intake on rest days

*Clinical eating disorders, such as anorexia nervosa or bulimia nervosa, are diagnosed according to specific and narrow criteria surrounding body weight and eating behaviours. Many people experience some degree of disordered eating which falls short of an official diagnosis. It is still crucial to identify and monitor these with help from a medical professional before a full blown eating disorder develops.

It’s incredibly hard to get an accurate idea of prevalence but current best estimates suggest eating disorders are twice as likely to develop among athletes than non-athletes (Torstveit et al., 2008). Eating disorders have the highest mortality rate among all mental disorder.

Since the initial signs and symptoms of RED-S tend to be relatively subtle in isolation, it can be easy for an athlete to dismiss them. Unfortunately, many athletes who suffer the consequences of RED-S may initially experience some desired outcome i.e. weight loss, desired aesthetic or performance advantage. Then, when correlation is confused with causation, it can fuel the fire to maintain the unhealthy behaviours behind the achieved outcome and ignore the warning signs until they become a bigger issue. By that point, the behaviours may well be ingrained and difficult to let go of - meaning a tendency to avoid seeking solutions that involve changing them (i.e. doing less and eating more).

Since causes of low energy availability range from unintentional on one end of a spectrum, to a diagnosable eating disorder on the other, there are multiple reasons that an athlete may be in a state of RED-S. If they aren't exhibiting any signs of disordered eating, it could be that the athlete is simply misjudging their nutritional requirements.

Though it's sometimes hard to believe when someone already seems to eat a great deal, it can incredibly easy to underestimate the nutrition required to match the demands of training. This isn't helped by the countless social media icons and bloggers who promote restrictive eating behaviours and provide misguided information on the internet.

An increase in training volume or intensity (when it isn’t matched with an increase in caloric intake) can lead to RED-S over a period of time. Even adding in extra drill sessions, strength and conditioning work, extended warm-ups or cool-downs can contribute to decreased energy availability if these activities are not compensated for with the right nutrition.

Thankfully, unintentional under-fueling should be relatively easily resolved once an athlete is armed with the right information. If you think this could be the cause of your athlete's issue, we strongly advise seeking help from a dietitian. Visit our resources page for recommendations.

A word of caution: Even unintentional under-eating can develop into something more intentional overtime. If, for example, the negative energy balance results in weight loss which brings about a short-term performance benefit, it can perpetuate a desire to maintain this weight, or lose more.

Torstveit, M.K., Rosenvinge, J.H. & Sundgot-Borgen, J. (2008). Prevalence of eating disorders and the predictive power of risk models in female elite athletes: a controlled study. Scandinavian Journal of Medicine & Science in Sports, 18, 108-118.