Discovering Low Energy Availability in Athletes: Causes, Effects, and Definitions

What are the "athlete triad," "relative energy deficiency in sport," and "low energy availability"? History and idea definition.

RED-S is a condition that happens when people who are physically active don't have enough energy in their body. This can cause problems with their body's systems like the endocrine system (which helps control the hormones in your body), the physiological system (which helps control how your body functions), the metabolic system (which helps control how your body gets energy from food), and the psychological system (which controls your thoughts and feelings). Low energy availability, or not having enough energy from food, is what causes these problems. The "triad" model also explains how low energy availability can cause problems with bones and the reproductive system in athletes. The RED-S model is similar to the triad model, but it also looks at how low energy availability can affect other systems in the body in both men and women (if you want to understand more about the RED-S and Triad model, please read at the science article).

Tests with female athletes

Energy availability is the amount of energy from food that is needed to keep the body working normally. Professor Anne Loucks did a study to see if exercise or low energy availability was the cause of problems with hormones in female athletes. She found that low energy availability was the cause of hormone problems, not exercise.

Diseases caused by

Eating disorders, osteoporosis (when bones become weak and can break easily), and menstrual dysfunction (when a woman's period is not regular) are some of the problems that can be caused by low energy availability in female athletes. Male athletes can also have problems with their bones and reproductive system because of low energy availability.

Energy balance simple explained

There are different ways to measure energy availability, but one way is to look at energy balance. Energy balance is the difference between the energy you eat and the energy you use. If you have a positive energy balance, it means you are eating more energy than you are using and you will gain weight. If you have a negative energy balance, it means you are using more energy than you are eating and you will lose weight. If you have no energy balance, it means you are eating the same amount of energy as you are using and your weight will stay the same.

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What exactly is RED-S?

Sports nutrition is now highly buzzed about the relative energy deficit in sport (RED-S), and for good cause. It is believed that the theoretical model known as the RED-S, which was first developed in 2014, may be able to explain the formation of a variety of indications and symptoms that might harm the health and performance of physically active people (both males and females). Endocrine, physiological, metabolic, and psychological dysregulations are some of these impacts, which are hypothesized to eventually have an impact on physical ability and performance.

RED-S explains the causes of a broad variety of symptoms and indicators that might harm the health and performance of physically active people (both sexes)

Typically, a person is referred to have "RED-S" when many of these systems exhibit abnormal function. It is believed that "energy availability" or more particularly "LOW energy availability" is what has caused these changes (or LEA, see explanation below).

What The Triad Is?

It's interesting that there is another model, known as the "triad" model, which also offers a theoretical foundation for comprehending the detrimental impacts of LEA. This model, which was initially referenced in the literature in 1993 and was officially formed by a committee of specialists in 1997, was originally known as the "female athlete triad." The discovery was made in an attempt to address the widespread occurrence of female athletes exhibiting the "triad" of symptoms of eating disorders, osteoporosis, and menstrual dysfunction (reduced energy availability).

We now have a better grasp of how to identify this ailment and what are the usual signs and symptoms owing to the decades of study that have strongly supported this paradigm. Parallels have been found between this disease and reports of bone and reproductive system dysregulation in exercising guys too in the "male athlete triad" more recently, in the past few of years.

Do the RED-S and triad models vary from one another?

The RED-S model, which was developed by a different team of academics and practitioners, is based on the triad but emphasizes two theoretical claims more strongly: 1) The potential impact on men as well as females, and 2) The potential impact on a wider range of systems/areas in addition to the bone and reproductive system. Due to its history, the triad model initially placed a greater emphasis on females, and the bulk (though not all) of the impacts were related to bone and reproductive function.

Researchers from all across the globe are working to support both ideas as we presently increase our knowledge of them. No matter the model, poor energy availability is at the center of these two crucial models and is believed to be the primary cause of all the indications and symptoms they describe.

What exactly is energy availability

Mathematically, energy availability is defined as the "dietary energy available to sustain normal physiological function" and is computed as follows:

Energy availability = (Daily energy intake - Daily exercise energy expenditure) / Fat Free Mass (FFM)

The difference between dietary energy intake and energy used during exercise, normalized to fat-free mass (the most metabolically active component of our body mass). The end result is the amount of dietary energy "available" (in kcal/kg FFM/day) to support healthy tissue and organ function (the energy necessary to maintain all the cells in your body functioning normally).

The outcome is the amount of dietary energy "available" (in kcal/kg FFM/day) to support healthy tissue and organ function.

This equation was used in important human studies under the direction of Prof. Anne Loucks to determine whether exercise stress *per se* or the quantity of energy available was the cause of endocrine reactions linked to the female triad (after factoring in exercise energy expenditure). This study demonstrated that limited calorie availability, not exercise stress, was what was causing hormone dysregulations.

Okay, I get that. But what does "LOW energy availability" mean?

The computation of energy availability may be done in a variety of ways, and while the idea behind it is similar to that of energy balance, it is distinct. It's important to note that an energy availability of 45 kcal/kg/FFM day is roughly equivalent to an energy balance of zero (no net loss or gain of body weight over time). Some people refer to this as normal or adequate energy availability. However, the explanation of how these differ is a bit longer than the length of a blog post allows.

It's crucial to understand that a 45 kcal/kg/FFM day energy availability is basically comparable to a zero energy balance.

According to Prof. Loucks' study, poor energy availability is instead defined as being at or below a daily threshold of 30 kcal/kg FFM/day, which has been shown to have a demonstrable impact on females' hormonal indicators for the reproductive system and bone metabolism. But in 3-6 day laboratory-based investigations, sedentary ladies were the major subjects of this crucial study. Is there a universal threshold of poor energy availability of 30 kcal/kg FFM/day? for further information on whether this threshold can be extended to fieldwork and to both sexes.

Deep dive sources

  1. Areta JL, Taylor HL, Koehler K. Low energy availability: history, definition and evidence of its endocrine, metabolic and physiological effects in prospective studies in females and males. Eur J Appl Physiol. 2021;121:1–21.
  2. Mountjoy M, Sundgot-Borgen J, Burke L, Ackerman KE, Blauwet C, Constantini N, et al. International Olympic Committee (IOC) Consensus Statement on Relative Energy Deficiency in Sport (RED-S): 2018 Update. International Journal of Sport Nutrition and Exercise Metabolism. 2018;28:316–31.
  3. De Souza MJ, Nattiv A, Joy E, Misra M, Williams NI, Mallinson RJ, et al. 2014 Female Athlete Triad Coalition Consensus Statement on Treatment and Return to Play of the Female Athlete Triad: 1st International Conference held in San Francisco, California, May 2012 and 2nd International Conference held in Indianapolis, Indiana, May 2013. British Journal of Sports Medicine. 2014;48:289–289.
  4. Loucks AB. Exercise Training in the Normal Female: Effects of Low Energy Availability on Reproductive Function. In: Hackney AC, Constantini NW, editors. Endocrinology of Physical Activity and Sport. Cham: Springer International Publishing; 2020 [cited 2020 Mar 31]. p. 171–91.

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