Energy Availability (EA)

What is energy availability (EA), and why does it matter?

This is a repost of my Instagram post:

The plain text of the slides can be found below the images.

What is Energy Availability (EA)?

Energy availability (EA) is the energy available after you subtract your exercise energy expenditure (EEE) from your dietary energy intake (EI). EA = EI - EEE.

EA is the remaining energy available for physiological functions, health, recovery, and training adaptations.

EA can be lowered by increased training and/or decreased food intake, and often unknowingly by increasing training volume, increasing recreational activity, and/or experimenting with skipping meals, fasting, exclusive diets such as “clean eating”, paleo, vegan, low-carbohydrate, ketogenic, and carnivore.

Low energy availability (LEA) is seen in athletes who are over-training, chronically dieting, and/or have disordered eating behaviours such as meal skipping, binge eating, restricting certain foods, and using laxatives or diet pills.

Low energy availability (LEA) affects hormones, metabolism, protein synthesis (e.g., bones, muscles, tendons), immune, cardiovascular, reproductive, and psychological health. Negatively impacts performance, progressive training adaptations, recovery, and body-composition. LEA impairs use of glucose and fat for energy, reduces oxygen delivery, lowers metabolic rate, increases fatigue, disrupts sleep, increases cortisol and cholesterol, decreases testosterone, oestrogen, growth hormone, lowers libido, disrupts menstrual cycle, and may lead to osteoporosis and injury (e.g., fractures).

Importantly, though weight loss requires and often signifies an energy deficit, low energy availability (LEA) is not always accompanied by weight loss.

Seen in normal weight female athletes without menstrual cycles (e.g., functional hypothalamic amenorrhea), as the body adapts to survive and maintain energy balance.

LEA leads to a negative energy balance and thereby weight loss because the body’s energy reserves (e.g., adipose tissue and body proteins) substantially contribute to fuel needs. However, longterm LEA causes metabolic and physiological adaptations in order to reduce total energy expenditure to prevent further weight loss and promote survival, whereby the body obtains a new energy balance steady state. Therefore, an athlete may be weight stable and not excessively low in body mass or body fat levels yet have impaired physiological function secondary to LEA.

Melin, A., et al. (2019). Energy Availability in Athletics: Health, Performance, and Physique.

EA is defined in kcal per kg of fat-free mass (FFM).

In female athletes, <30 kcal/kg FFM/day is typically defined as clinical LEA, causes severe endocrine and metabolic alterations, and loss of reproductive function. However in some women, amenorrhea (absence of menstruation) has been shown to occur at >30 kcal/kg FFM/day. Declines in insulin, IGF-1, thyroid hormone (T3), bone protein synthesis, and bone mineralisation can occur within 5 days of the onset of LEA.

Subclinal LEA is 30-45 kcal/kg FFM/day. EA of at least 45 for sedentary eumenorrheic (menstruating) normal weight women, and 40 for exercising men appears to ensure optimal EA for physiological functions.

The Relative Energy Deficiency in Sport (RED-S) model describes health outcomes and potential performance effects resulting from LEA in athletes.

  • High EA - Healthy weight gain or weight maintenance. Training at moderate intensity ~1.5–2 hr/day.
    • Females: >45 kcal/kg FFM/day
    • Males: >40 kcal/kg FFM/day
  • Optimal EA - Weight maintenance providing adequate energy for all physiological functions. During periods with injury with alternative or rehabilitation training at low/moderate intensity ~1.5 hr/day.
    • Females: ≥45 kcal/kg FFM/day
    • Males: ≥40 kcal/kg FFM/day
  • Subclinical LEA - May be tolerated for short periods during a well-constructed weight-loss program.
    • Females: 30–45 kcal/kg FFM/day
    • Males: 30–40 kcal/kg FFM/day
  • Clinical LEA - Health implications with impairment of many body systems including training adaptation and performance.
    • <30 kcal/kg FFM/day

A female athlete (60 kg, 18% body-fat) consumes around 2200 kcal (EI) per day. She starts a new training program which expends ~500 kcal (EEE) over the 2 hour session.

60 kg * (1 - (18/100)) = 49 kg FFM
2200 kcal (EI) - 500 kcal (EEE) = 1700 kcal
1700 kcal / 49 kg FFM = 35 kcal/kg FFM (Subclinical LEA)

Recommendation of >45 kcal/kg FFM/day for maintaining weight whilst training ~1.5-2 hours at moderate intensity…

46 kcal * 49 kg FFM = 2254 kcal
2254 kcal + 500 kcal (EEE) = 2754 kcal (EI)
2754 kcal (EI) - 500 kcal (EE) = 2254 kcal
2254 kcal / 49 kg FFM = 46 kcal/kg FFM (High EA)

2754 kcal covers her training session expenditure, and provides the essential available energy for good health, recovery, and to support progressive training adaptations.

Body-composition testing services are easily found, and can determine your fat-free mass (FFM) with various levels of accuracy at relative costs. If possible choose “DEXA”, followed by “Bod Pod”, “ISAK”, and finally “Bioimpedance Analysis (BIA)”. Bathroom scales use BIA and have a margin of error of >5%, so be wary.

FFM accuracy will likely impact calculations by ~100-200 kcal, but as your aim should always be about finding the maximum you can eat to support your body, always choose the higher kcal intake.

Estimating your exercise expenditure is not so easy. But search for a “MET calculator” online which can help you.

IMPORTANT, if you are in any doubt about anything whatsoever in regards to this post, please contact me or a Sports Dietitian or nutritionist. We are here to help you make appropriate and healthful decisions.

BASEM: Health4Performance - To raise awareness and improve identification and effective management of athletes/dancers at risk of RED-S. For those concerned about RED-S, there are signposts to the appropriate personnel and resources.

#TRAINBRAVE - The #TRAINBRAVE campaign aims to inspire more athletes to share their stories and raise awareness of the risks of eating disorders and RED-s.

The EN:SPIRE Clinic - The UK’s first Sport and Dance RED-s, Overtraining and Eating Disorder Specific recovery clinic.

Energy Availability (EA) Calculator - May aid in understanding your current EA and required energy intake to reach EA guidelines.