Relative Energy Deficiency in Sport (RED-S) sheds light on the complex factors that affect athletes and active individuals. At its core, RED-S is inadequate energy availability (EA) relative to an athlete’s volume or intensity of training or competition.

Previously, this was known as the “female athlete triad” characterized by three key issues, seen in some females involved in competitive sports or intense workouts. These include

1.     Disordered eating (e.g. anorexia nervosa, bulimia nervosa)

2.     Amenorrhea (loss of regular menstrual cycle)

3.     Osteoporosis (weakening of bones due to loss of bone mineral density)

This definition does not include the broad spectrum of factors affecting active men and women today. The prevalence of issues such as eating disorders is higher in both adolescent and adult women than men (20% and 13% vs. 8% and 3%, respectively). However, both men and women face similar pressures and body-focused expectations. In fact, some studies have found body image pressures and distortions to be even greater for men.

What is adequate energy availability?

“Adequate energy availability” is having enough energy (calories from protein, fat and carbohydrate) to support the body’s level of physical activity plus daily living functions. For active individuals, EA is the energy remaining to support all body functions after accounting for the energy needed for exercise. In low EA, the amount of energy consumed isn’t enough for exercise and body functions.

For example, Jim consumes around 2000 calories/day and always makes sure he eats a balanced breakfast, lunch and supper. Jim has been very cautious when it comes to making “healthy” food choices and spends a lot of time worrying about his eating. He finds that he often misses his snack due to his busy work day or because he is trying to make it to the track to train for his half marathon coming up. On average, he burns around 600 calories/day training and his metabolic rate is 1800 calories/day, when all his additional movement and body functions are taken into account. He has been feeling exhausted by 4 pm, is losing weight rapidly and can’t seem to get over his cold.

Jim is in a state of inadequate energy availability (low EA).

Consequences of RED-S


1)     Decreased hormone production: Hormone production happens only if you consume an adequate amount of energy, particularly fat and protein. With negative energy balance, hormone production (e.g. estrogen and testosterone) is reduced, directly impacting other body functions.

2)     Depleted energy stores: Low energy availability can result in reduced glucose (energy) available for use in the body, resulting in the use of stored fat for energy and an overall reduced metabolic rate. 

3)     Nutritional deficiencies: Those who are under-fueling their bodies often present with nutritional deficiencies such as anemia. Low iron can increase fatigue and risk of injury.

4)     Impaired growth and development:A reduced metabolic rate directly reduces the production of growth hormones and decreases muscle protein synthesis. This affects growth and development.

5)     Impaired menstrual function:Withreduced hormone production and low body weight, females in negative energy balance can experience a loss of menstruation or an irregular menstrual cycle. This may result in anxiety, unexpected pregnancy or infertility.

6)     Poor bone health: Loss of bone mass is often a result of nutritional deficiencies and reduced production of estrogen in females and testosterone in males. In extreme cases, bone loss can be irreversible and result in stress fractures.

7)     Depression and anxietyThese conditions can both cause, or occur as a result of, low energy availability, impacting an individual’s optimal performance. These conditions can also result in impaired gastrointestinal function and stomach upset.

8)     Heart disease: Low energy availability can result in less favourable blood lipid profiles (i.e. increased “bad” cholesterol and reduced “good” cholesterol) increasing risk of heart disease.

9)     Increased risk of illness:Adequate protein is required to build antibodies. An energy deficit puts you at increased risk of illness due to a reduction in antibody production.

Early signs of RED-S

Perhaps you have experienced one or more of these conditions and have never really considered that it could be linked to low EA. A common misconception about RED-S is that it only affects elite athletes or individuals involved in competitive sports. However, with our health-fixated culture, orthorexia has made developing RED-S more likely, even for recreational individuals (like Jim).

With social media providing access to “before and after photos” and “clean eating” posts, well-intentioned changes to eating and physical activity have the potential to result in serious health consequences. Because RED-S can be intentional or unintentional, it may be misdiagnosed or overlooked.

Take some time today to check in with yourself by asking these questions:

  • How are my energy levels throughout the day?
  • Do I take time to eat consistently throughout the day (every 2-3 hours)?
  • What is my mindset around my food choices? Do I experience guilt/shame with food?
  • What is my motivation to exercise? Do I experience guilt/shame with exercise?
  • Have I been sick frequently lately?
  • Have I been losing weight unintentionally?

These questions will allow you to recognize early signs and symptoms of RED-S. A formal table for classification of risk of RED-S is available here. However, it is advisable to consult with a physician and registered dietitian to diagnose specific conditions, such as an eating disorder, or to assess bone mineral density.

Bringing awareness to RED-S and the impact it has on both males and females is essential to ensure you are maintaining a healthy relationship with food, fitness and yourself.

AFLCA Members

Are you looking for practical nutrition tools for your clients? Log in to the AFLCA Members section of the website and order free resources today! 



Share this post

Barbara Winzeler, RD

Registered Dietitian

Barbara (BSc, RD) is an Edmonton-based registered dietitian and blogger for Nourish Move Thrive®. She enjoys helping her clients develop healthy relationships with food and themselves.

Sign up to receive Nourish Move Thrive updates twice a month!