Energy availability in athletes: How important is the concept of inadequate energy intake?

Energy availability in athletes is a growing area of focus for sports nutritionists. But how important is the concept of inadequate energy intake for both health and performance?

Original study

Charlton, B. T., Forsyth, S., & Clarke, D. C. (2022). Low Energy Availability and Relative Energy Deficiency in Sport: What Coaches Should Know. International Journal of Sports Science & Coaching, 17479541211054458.

Click here for abstract

Background & Objective

I have worked in professional sport for nine years now and have certainly seen elements of disordered eating and eating disorders with the athletes I have supported in rugby, football and boxing. I’m not convinced many of the athletes knew they had various traits of disordered eating patterns, nonetheless, let’s dive into this area a little deeper.

Since 1992, the term Female Athlete Triad has been used to describe the combination of amenorrhea, osteoporosis, and disordered eating. However, developments have been made and as of 2007, the Triad is now described as a disorder that features menstrual dysfunction, altered bone health and low energy availability (LEA) with or without an eating disorder.

In 2014, the International Olympic committee produced a consensus statement which encompasses the full scope of this symptomology and was given a new term, the Relative Energy Deficiency in Sport (RED-S). Importantly it was highlighted that this new framework includes males and recreational athletes. The video link below is an outstanding listen on this.

The purpose of this review was to synthesise available evidence and provide coaches with the scientific basis underlying the concepts of LEA disorders. An overview of RED-S is provided and importantly nutritional guidelines to help prevent LEA.

What They Did

The authors synthesised evidence from peer-reviewed studies published between 1986 and 2021 that they believe are essential for coaches to know so they can better guide their athletes and prevent LEA.

The review is split into the following sections:

1. The female athlete triad and relative energy deficiency in sport: diagnosis, mechanism, and prevalence 
2. Performance and health impairments of LEA and RED-S which is then further broken down to:
   A) Hormonal and metabolic function
   B) Bone health
   C) Cognitive ability and mental health 
3. Nutritional practices to help prevent LEA and RED-S
4. Monitoring athletes for risk of LEA
5. Supporting athletes at risk of LEA

What They Found

The signs of the female athlete triad exist on a continuum from healthy to pathological. Optimal energy availability will result in normal menstruation and optimal bone health.  Low energy availability will result in hypothalamic amenorrhea and unfortunately can lead to Osteoporosis. Males show signs and symptoms of the Triad with the exception of irregular menstrual patterns. Hence the adoption of RED-S defined as “impaired physiological functioning caused by relative energy deficiency and includes but is not limited to, impairments of metabolic rate, menstrual function, bone health, immunity, protein synthesis and cardiovascular health.”

Commonly reported performance impairments of RED-S are broken into two areas – physiological and psychological. The physiological components include decreased training response, glycogen stores, endurance performance and muscle strength. The psychological effects include decreased coordination, concentration, impaired judgement, depression and irritability. RED-S impairs the physiological functions that support athlete growth, development, health and performance. The main effects can impact the endocrine system including menstrual function, bone health and metabolism.

The most effective approach to mitigate the adverse performance and health consequences of RED-S is through proper nutrition and the need to obtain sufficient total energy from food. Energy requirements will depend on sex, body mass, biological age and energy expenditure from training and competing.

In addition to carbohydrate, protein and fat, micronutrient intake is important. Calcium, Iron and Vitamin D should be consumed in line with recommendations to ensure adverse health effects are not present.

Monitoring early signs of LEA include injury, illness, prolonged under performance compared to normal (one of the most obvious), feeding and diet behaviours outside of what you would expect, athlete self-criticism, social withdrawal and depression.

They found the first step in supporting your athlete through LEA is to document the signs and symptoms that you observe. The next step is to speak with the athlete (and parents if a youth) stating your observations are consistent with those of RED-S. The final step is to encourage the athlete to consult with a sports medicine physician who is a specialist in managing these disorders.

Practical Takeaways

Several challenges hinder the diagnosis of RED-S. The first is the spectrum of dysfunction that can present between individuals. The second challenge is the accurate assessment of energy intake. The third challenge is that RED-S specific questionnaires are still being developed and validated almost every month. The podcast below discusses this in more detail.

LEA is the underlying mechanism that causes RED-S. Energy availability is calculated as energy intake minus exercise energy expenditure, with each term in the equation expressed in units of kilocalories per kilogram of fat-free mass. 

The accepted daily energy expenditure for female athletes ages 11 to 18 is approximately 2200 kcal, while that for males of the same age range is 2500-3000 kcal. 

Athletes are advised to consume 5-12g of carbohydrate per kg of body mass per day, however in practice I would never have an athlete reaching 12g per kg of body mass! (Maybe in endurance cycling but certainly not football or rugby). My advice would be to periodise carbohydrate intake aligned to the specific body composition, training, and competition goals – i.e., fuel for the work required. Protein intake between 1.2-1.7g per kilogram of body mass per day is suggested and this should increase 1.2-1.5 times the athlete’s body weight if they are injured. Fat intake should equate 15-30% of total intake. 

When supporting athletes at risk of LEA, the earlier the plan of action is implemented, the sooner the athlete may be able to return to form and the lower the risk of long-term impacts on physical and mental health. The coach should always communicate with the athlete and ensure conversations remain private whilst respecting the athlete’s autonomy (it is their choice to seek medical support). 

Finally, and a very important point, coaches must respect their scope of practice; they are not medical professionals, and they cannot diagnose illnesses, injuries or disorders.

James Morehen’s Comments

“All athletes are at risk of LEA but is it a problem for everyone? Some of the boxers I work with experience elements of under-fuelling, but this is strategically planned into their overall nutritional strategy to help them make weight. Personally, I think acute bouts of LEA are ok, but if this transitions into chronic periods of time, then that’s when the health and performance problems will arise.

“As nutritionists, we are uniquely positioned to be able to spot the early signs of eating disorders or disordered eating before these manifest into LEA and RED-S. I would encourage other practitioners to quickly get to know their athletes’ habitual eating behaviours at meal times and observe if these change from the norm.”

Want to learn more? Then check these out…

Watch this video
Listen to this podcast
Read this infographic

Want more research reviews like this?

Every coach understands the importance of staying up-to-date with the latest sports performance research like this, but none have the time, energy, or even enjoys spending hours upon hours searching through PubMed and other academic journals. Instead, your precious time is better-spent coaching, programming, and managing all the other more important aspects of your job.

The solution…

The Performance Digest
The Performance Digest is a monthly summary of the latest sports performance research reviewed by our team of hand-selected experts. We sift through the 1,000+ studies published in the realms of sports performance every, single month and review only those which are important to you. Each monthly issues contains 15 research reviews in all of the following disciplines:

Coaching Science

Strength & Conditioning

Technology & Monitoring

Fatigue & Recovery

Youth Development

Nutrition

Injury Prevention & Rehab

This comprehensive topic base ensures you’re constantly expanding your knowledge and accelerating your career as quickly as humanly possible. The reviews are also hyper-focused, 1-page summaries, meaning there’s no jargon or wasted time. We cut right to the chase and tell you what you need to know so you can get back to coaching.

Join the thousands of other coaches who read it every, single month. Click here to get instant access for free…