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RED-S: Understanding the Condition that Threatens Athletes' Health and Performance

Updated: Jun 15, 2023

Relative Energy Deficiency in Sports, also known as RED-S, manifests as an imbalance of energy available for the individual’s health and performance requirements. This results not only in inadequate energy for optimum athletic performance but also in insufficient energy to sustain optimal health, affecting a variety of physiological systems.

You can consult our specialised sports dietitian from this link to ensure you are fuelling your body with enough energy.

Athletes running in a competition
Relative energy deficiency in sports manifests as an imbalance of energy available for the individual’s health and performance requirements.

This blog includes the following:

What is RED-S

RED-S is a condition that occurs when an athlete does not consume enough energy to support their physical activity levels. This energy deficit and disordered eating patterns can cause rapid weight loss, which negatively impacts various physiological systems, including the endocrine, menstrual, musculoskeletal, immune, and cardiovascular systems.

The underlying cause and effect of relative energy deficiencies in sports can be severe if not treated immediately. Your sports performance may be limited due to a downregulation of physiological functions. Symptoms of irregular menstruation, decreased bone strength, and fatigue is most commonly experienced.

Keep in mind that your body functions from the energy on the inside. You must receive enough nutrients to support the efforts of your training and everyday work to be as effective and productive as you CAN be.

Green leafy vegetables and a portion of meat
Consuming enough food to support demands of training is necessary in overcoming RED-S

What health consequences are experienced with RED-S

Relative Energy Deficit in Sports can affect many physiological functions and athletic performance. Below is a list of the three most commonly experienced athletes with RED-S.

Decreased Energy Availability

Athletes suffering from RED-S can experience a loss in their strength and concentration due to a lack of energy availability. The main cause of RED-S is ongoing inadequate energy intake to support energy output = decreased energy availability.

Woman running in a race
Inadequate energy intake to support energy output results in decreased energy availability.


Losing your menstruation can indicate that your body is producing insufficient amounts of estrogen and an imbalance of other reproductive hormones. It can majorly affect your bones resulting in osteoporosis. Menstruation is an essential factor affecting both estrogen levels and bone health.

A red popsicle symbolizes menstruation
Amenorrhea is the absence of menstruation, often defined as missing one or more menstrual periods. Primary amenorrhea refers to the absence of menstruation in someone who has not had a period by age 15.


Osteopenia, also known as low bone mineral density, can drastically increase your chances of injury during training. If you are not eating and recovering right, the chances of having stress fractures are very high.

Overall, you can see how these three health consequences all contribute to the severity of each. For example, long-term decreased energy availability leads to amenorrhea, and the decreased estrogen and hormonal levels are what impact bone mineral density.

An x-ray of broken a broken clavicle
Amenorrhea may signal the start of estrogen insufficiency, which can have a negative impact on peak bone mass and the chance of developing osteoporosis in the long run.

Other symptoms of RED-S may include:

  • Weight loss/underweight

  • Recurrent illnesses e.g. colds and flu’s

  • Mood Changes

  • Delayed/disordered growth/development (children and teenagers)

  • Iron deficiency

  • Severe RED-S can affect the heart.

How does RED-S affect an athlete’s performance?

RED-S has a variety of detrimental effects on athletic performance. The development of weariness happens more quickly when working muscles have less energy available to them.

1. Reduced muscle growth and strength

Numerous causes, such as changes in neuromuscular function (how the nerve system regulates muscles), cortisol (the stress hormone), and low testosterone, frequently result in a reduction in muscle growth and strength (in both men and women). These reductions typically counteract any advantages in "power to weight ratio" that the athlete would seek by pursuing extreme leanness.

A boxer with less muscle
With reduced energy availability, muscular growth and maintenance is hindered. This can affect sports performance and the athlete's ability to progress

2. Reduced recovery

This makes it harder for the body to save adequate energy for successive workouts, raising the possibility of overtraining and persistent weariness. In order to adjust to training, energy is needed. Low energy availability prevents muscle, cardiovascular, and cardiovascular adaptation and development from happening as effectively, which impedes training success.

Exhausted athletes laying on the ground after a run.
When an athlete doesn't effectively recuperate from repeated, hard exercise, overtraining syndrome develops. This condition can lead to tiredness, deteriorating performance, and even injury.

3. Increased risk of injury

Sprains, strains, and bone-impact injuries can heal more slowly or become chronic if there is insufficient energy available to mend them. Stress fractures resulting from decreased bone density are frequent and can cause weeks or months of training to be missed.

An injured woman's leg, doing some therapy
When there is insufficient nutrients to support tendons, ligaments and muscles, athlete's become more prone to injury when their body is unable to support the impacts, weight and speed of their training.

How to Prevent RED-S

Consume a balanced and adequate diet:

The best way to prevent RED-S is to maintain a balanced nutrition intake that matches the energy requirements of the individual’s life and sporting demands. Athletes should work hand in hand with a Sports Dietitian to develop individualised nutrition plans based on their training intensity, training phase, and upcoming competition and sporting goals. The number of calories, carbohydrates, protein, and fat varies among athletes and is not a one size fits all approach. Consulting with a sports dietitian will make this process easier and allow the athlete to know what their body requires to perform optimally.

Avoid losing weight quickly:

Depending on the athlete's body composition goals or demands of their sport, they might try to lose weight quickly to meet the requirements of a weight class, suggestions from their coach, or external pressures. Losing weight is not always a problem in sports; however, rapid weight loss can impact athletes' health and performance. Seeking assistance from a Sports Dietitian can assist the athlete in reaching weight loss goals in a gradual and sustainable manner. It can reduce its impact on sports performance and maintain a healthy relationship with food. Athletes involved in weight-making sports are encouraged to seek nutritional advice at least 12 weeks before the competition date to ensure adequate time to make healthy changes.

Avoid over-exercising:

Athletes’ nutritional demands are incredibly high based on their energy requirements for their sport. Excessive exercise can be prescribed, or external pressures to complete additional training sessions can cause the athlete to become more of a nutritional deficit and find it hard to meet requirements due to limited time. As an athlete, ensure that you know which training sessions, exercises, and intensity are required to progress in your sport and avoid completing training which is proving no true benefit to your goals as an athlete.

How to Recover from RED-S

Gradually increasing food intake with the following tips:

1. Start small:

Progressively increase your food consumption to gradually match your energy expenditure. Facilitating the change slowly will ensure that you reduce the shock to your body and allows you to adapt easier.

2. Pay attention to nutrient-dense foods:

Prioritise consuming a whole-food diet, rich in vitamins, minerals, and other necessary nutrients. Lean protein sources, nutritious grains, fruits, and veggies are a few excellent examples.

3. Eat more frequently:

Try to spread out your meals throughout the day by eating smaller, more frequent meals rather than three large ones each day. This may enable you to eat more calories overall and supply your body with continuous energy without feeling too full!

4. Hydrate:

Recovering from RED-S requires maintaining hydration. Aside from electrolyte-rich beverages like sports drinks or coconut water, ensure you drink enough water.

5. Supplement with necessary vitamins and minerals:

Get regular blood tests and check if you are meeting your optimal ranges for these nutrients. Seeking help from a health professional who is equipped in understanding optimal ranges will then be able to provide you with a necessary supplement plan.

Keep in mind that the objective is to increase your food intake in a healthy, sustainable manner that meets your body's demands and aids with RED-S recovery. To create a customized nutrition plan appropriate for you, speak with a healthcare practitioner or a registered sports dietitian.

Types of whole grain diet
Gradually increasing your food can reverse the effects of low energy availability and RED-S symptoms.

Repair relationship with food (if disordered eating patterns are prevalent)

If disordered eating behaviors are pervasive during a RED-S recovery phase, it could be beneficial to:

1. Seek expert assistance:

You may address any disordered eating behaviors and create healthy habits by speaking with a qualified dietitian, sports dietitian, or psychologist.

2. Practice mindfulness:

If you have a history of disordered eating, mindful eating can help you pay close attention to your hunger level and fullness cues.

An image of a woman practicing mindfulness in an open space
Using breathing techniques, guided imagery, and other stress-reduction techniques are all part of practicing mindfulness.

Understanding body's requirements for sporting demand and how it affects performance

It's vital to understand the body's demands for athletic demand and how these needs might affect performance when recovering from RED-S. Monitoring your energy levels, your ability to recover, and how your body responds to different forms of exercise may give useful insights into your dietary needs.

By taking a thorough approach to understanding your body's demands, you may make the necessary changes to your diet and eating habits to improve your athletic performance and general health while recovering from RED-S.

Potential requirement for increasing body weight to a healthy range for the athlete

Altering body composition, and in particular, body weight to the individual’s healthy range may indeed be necessary for the athlete. This can enhance general health and performance by restoring hormonal balance. However, it is critical to do so in a slow and regulated manner to ensure that the weight gain is related to an increase in muscle mass rather than just body fat. A healthcare expert or accredited sports dietitian can assist the athlete in making safe and successful modifications to their nutrition and physical activity to attain a healthy weight.

At the Olympic trials in Eugene, Oregon, Annie Kunz competed in the women's heptathlon 100-meter hurdles. Image resource www.npr.orgathlete who looks healthy while doing sport
Due to their high daily energy expenditure, weight management for athletes and active people is distinct; as a result, the emphasis is typically centered on altering the nutrition side of the energy balance equation.

To put it all together, RED-S can negatively affect athletic performance by reducing energy availability to working muscles, leading to a more rapid onset of fatigue, decreased muscle size and strength, impaired recovery, hindered adaptation to training, and increased injury risk. The best way to prevent RED-S is to maintain a balanced diet that matches the athlete's energy requirements and, when body composition changes are necessary, seek help from an accredited sports dietitian.


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