Relative Energy Deficiency In Sport -How It Affects A Runner’s Energy

A couple of decades ago, there was a condition frequently seen in competitive female athletes, particularly in sports that emphasize a lean physique or that involve a high energy output, including distance running, gymnastics, figure skating, and cross-country skiing, termed the female athlete triad.

This condition was characterized by the presence of three interrelated symptoms: disordered eating with a restricted caloric intake, amenorrhea (the absence of the menstrual period), and low bone density.

It was thought that athletes who restricted their caloric intake would lose too much body fat, and menstruation would stop. This, in turn, would cause deleterious consequences to bone health because estrogen is necessary for healthy bone development.

In more recent years, the female athlete triad has been replaced with a condition termed Relative Energy Deficiency in Sport, or RED-S. 

But, what is RED-S? How does relative energy deficiency in sport affect your athletic performance and health? Keep reading to find out!

In this guide, we will look at: 

  • What is Relative Energy Deficiency in Sport?
  • Symptoms of RED-S
  • Treating Red-S In Athletes

Let’s jump in!

A thin person, hand holding her up against a wall.

What is Relative Energy Deficiency in Sport?

Red-S was introduced to replace the female athlete triad by the International Olympic Committee in 2014.

RED-S can lead to a sequela of adverse effects on nearly every body system and can compromise athletic performance as well as long-term health if not treated and corrected, so early recognition and treatment are crucial. 

Although there are some overlapping characteristics between the female athlete triad and RED-S, there are some distinct differences that make relative energy deficiency in sport more applicable to a wider range of athletes.

One of the primary differences between the classic female athlete triad and RED-S is that RED-S can affect male and female athletes equally across all ages, levels, and sports.

More importantly, as the full name of RED-S (Relative Energy Deficiency in Sport) indicates, RED-S syndrome is characterized by a relative lack of available calories. 

One of the problems with the female athlete triad framework is that it focuses mostly on caloric restriction, insinuating a degree of anorexia or other eating disorder-like behavior. 

A thin runner in a sports bra and tights.

Although this isn’t necessarily wrong or inappropriate in all cases, it is also possible to experience the other two components of the female athlete triad (amenorrhea and low bone density) without deliberately or even unconsciously restricting caloric intake. 

It is possible to be in a relative energy deficit if you are burning so many calories through exercise training. 

You may still be eating what may seem like plenty of calories, but when the caloric balance is investigated in detail, the number of calories you are eating is not sufficient for the number of calories you are burning. 

In this way, it is possible to be suffering from RED-S without having an eating disorder or deliberately restricting your caloric intake. 

You may simply be underestimating the number of calories you need to be eating based on how much exercise you are doing. 

Additionally, the wider scope of relative energy deficiency in sport can help identify athletes at risk or who are suffering from RED-S syndrome who are deliberately overexercising but who do not necessarily have an eating disorder that meets the traditional diagnostic criteria set forth in the DSM-5.

An exhausted runner leaning on the guardrail of a bridge.

Because of the stigma that is attached to anorexia and eating disorders, a diagnosis of the female athlete triad was also somewhat stigmatized, and there was a tendency for diagnosticians to focus on only specific high-risk groups, such as competitive female athletes in sports that emphasize a lean physique and low body weight.

One of the good things about relative energy deficiency in sport is that there doesn’t seem to be quite the same stigma attached to the condition, allowing athletes who suffer from it to feel more comfortable speaking out about it.

This, in turn, helps raise awareness and may help other recreational athletes who are at risk or are currently suffering from relative energy deficiency in sport to seek treatment.

Unfortunately, despite the improvements in replacing the female athlete triad with RED-S—namely in the fact that it occurs equally among male and female athletes from all levels and across all sports, and that it isn’t necessarily caused by disordered eating but rather just an overall relative caloric deficit—RED-S is still often overlooked by coaches, athletic trainers, and physicians. 

It is often not diagnosed until the athlete experiences a severe injury or mental breakdown due to underlying relative energy deficiency in sport.

Some athletes and sports professionals have made efforts to increase awareness and access to resources for RED-S. 

For example, Team GB runner Pippa Woolven, who suffered from the condition for quite a number of years, established an organization called Project RED-S to provide an online resource for athletes to obtain proper medical, nutritional, and psychological support when dealing with relative energy deficiency in sport.

A person making a pained face.

Symptoms of RED-S

Much like in the case of the female athlete triad, for females who suffer from RED-S prior to menopause, one of the common side effects of the condition is hypothalamic amenorrhea. 

This refers to the absence of menstruation due to low levels of hormones produced by the hypothalamus that otherwise control a healthy menstrual cycle.

The reason that the menstrual cycle can stop when you are in a relative energy deficit is that the body needs a certain amount of energy to produce the reproductive hormones that are required for the menstrual cycle.

Unfortunately, the consequences of hypothalamic amenorrhea caused by relative energy deficiency in sport are not isolated to just the inability to get pregnant while suffering from the condition.

A tablet that says Amenorrhea and a stethoscope.

Estrogen plays numerous essential roles in the female body, including supporting proper bone health, cardiovascular health, cognitive health, and mood stability.

Therefore, the effects of RED-S on the female body can be far-reaching and surprisingly long-lasting, even once the condition has resolved if it persisted for many years.

Males who suffer from RED-S are not immune to adverse hormonal changes and systemic deleterious effects of the condition.

Much in the same way that the female body needs an adequate amount of energy to produce estrogen and female sex hormones (as well as androgen hormones such as testosterone), the male body needs enough energy available to produce testosterone.

Male athletes who suffer from relative energy deficiency in sport often have clinically low levels of testosterone, with resultant symptoms such as decreased muscle mass, decreased athletic performance, decreased sexual performance, hair loss, and infertility.

In addition to hormonal imbalances and related consequences, RED-S can increase the risk of injuries and illness, compromise recovery, decrease performance, and lead to fatigue.

A runner sitting on a cement bench exhausted.

Treating Red-S In Athletes

Recovery from RED-S often involves a multidisciplinary approach, targeting nutrition, training, and psychological support, depending on the individual and the primary underlying cause for the relative energy deficit. 

In most cases, there is some amount of reluctance to consume enough calories, whether diagnosable as a clinical eating disorder or more along the lines of disordered eating patterns. 

These issues are often not solvable by just seeking nutrition support in terms of what the athletes should be eating, but also addressing the underlying psychological difficulties or anxieties with increasing caloric intake or eating certain types of foods that the athlete deems “unhealthy.”

The athlete may or may not need to stop training or participating in their sport, depending on the severity of the condition and any current clinical manifestations. 

In many cases, RED-S is not even diagnosed until a severe injury has occurred as a result of prolonged relative energy deficiency in sport. 

A runner bending down.

In these cases, the athlete may be forced to stop training or significantly reduced training, which can at least temporarily help restore energy balance. 

However, it is important to set the athlete up for future success once the injury has healed so that he or she can also recover from RED-S. 

Again, this comes down to trying to identify underlying causes and whether the athlete has been deliberately overexercising or overtraining or was simply unaware of how many calories he or she was burning and eating.

Psychological support is often necessary to help the athlete establish a healthier relationship with their body, their diet, and their exercise patterns, as well as to derive meaning and value in other aspects of their life so as to put less emphasis on their sport and their physical body. 

Again, this may or may not be necessary, depending on the individual situation.

A bowl of cereal, fruit and granola and a person making heart shape with their hands.

Overall, the key to successfully treating RED-S, recovering a healthy relationship with food and exercise, and restoring health is to identify the issue as soon as possible and take a multi-pronged approach to treatment.

Athletes who believe they are potentially suffering from relative energy deficiency in sport should be encouraged to seek support. 

The more the athletic and medical community can do to destigmatize the condition and bring an open dialogue to RED-S, the easier it will be for athletes to seek the support they need to get on the road to recovery.

For more information on how many calories you should consume as an athlete, check out our guide: How Many Calories Should A Runner Eat? Calculate Your Total.

A happy runner running on gravel.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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