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Metabolic Health

Low energy availability and blood glucose levels

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Low energy availability and blood glucose levels
Good morning Vibers! How’s your week going? To brighten up your day, we’re bringing you a new blog post, which might introduce you to a new concept: energy availability. This concept is relatively new in the field of sports nutrition and refers to the amount of energy provided by the diet per kilogram of lean body mass. Keep reading to learn more about low energy availability and blood glucose.
 
Over the past few weeks, we’ve been evaluating the blood glucose curves of our clients and have noticed some trends related to low energy availability. A deficient diet in a person or athlete can not only affect their performance but also other aspects of their health. Therefore, it’s crucial to understand how our bodies function in this situation.

What is energy availability?

Energy availability (EA) is defined as the amount of dietary energy available to maintain physiological functions (thermoregulation, immune system maintenance, growth, reproduction, etc.) after subtracting the energy expenditure from exercise. Therefore, the concept of energy availability is closely related to the proper functioning of our bodies.

When energy availability falls into a negative balance, the human body reacts by minimizing the energy required to perform the basic physiological functions mentioned earlier. This negative balance of energy availability is known as low energy availability. This occurs when the calories consumed are not sufficient to support the energy expenditure from exercise, and as a result, physiological processes become compromised.

💡 When the calories consumed are insufficient to support energy expenditure, it is considered low energy availability.

Insufficient EA can develop due to four main factors: eating disorders, weight loss restrictions, lack of appetite induced by exercise, or excessive exercise.

But how can energy availability be calculated? It is calculated using the following formula (1):

EA = Energy Intake (EI) (Kcal) – Exercise Energy Expenditure (EEE) (Kcal) / Fat-Free Mass (FFM) (Kg)

Imagine we have a female runner weighing 46 kg with 15% body fat. The amount of lean body mass would be 39 kg, which can be calculated through anthropometric measurements or with a bioimpedance scale. The runner’s energy intake is 2400 kcal/day, and her exercise energy expenditure is 1050 kcal/day.

EA = 2400 kcal – 1050 kcal/39 kg = 34.6 kcal/kg per FFM

Therefore, after using the equation and calculating this woman’s energy availability, it must be assessed whether her levels are adequate. Values <30 kcal/kg are considered low energy availability. However, optimal levels are considered to be 45 kcal/kg. In conclusion, the female runner is not in a state of low energy availability, although she could increase her energy intake to reach the established optimal levels.

At Glucovibes, through our app, we have tools and mechanisms to identify low EA, as we see it reflected in blood glucose levels.

Low energy availability and performance

Low energy availability negatively impacts many bodily functions. For example, in women, it is very common to see its impact on the suppression of the reproductive system and the disruption of the menstrual cycle, as a mechanism to conserve energy. Other hormonal pathways are also altered, leading to consequences related to the endocrine system. These include elevated cortisol levels, and reductions in triiodothyronine (T3), luteinizing hormone (LH) pulsatility, and hypoestrogenism.

Menstrual dysfunction related to low EA is associated with a higher risk of stress-related bone injuries that can affect training and competition. Therefore, low EA can impair not only health but also sports performance due to the harmful endocrine effects associated with it. In this sense, multiple studies associate low EA with decreased sports performance. This drop in performance is associated with other related parameters. For example, an interesting study concludes that decreased neuromuscular performance is associated with lower FFM in the leg, low glucose, estrogen, and T3 levels, and elevated cortisol (2).

In this regard, blood glucose is a sensitive parameter that allows us to identify symptoms of low EA, especially in the long term or chronically. The authors of a study proposed that, as a result of insufficient EA, consistently low blood glucose levels could lead to increased cortisol and reduced T3, as well as decreased muscle mass in the long term, all of which have been associated with decreased neuromuscular performance (3). We can confirm these results through our blood glucose and lifestyle analyses, as we are already doing with various users of our app.

How to avoid low energy availability

As mentioned earlier, to avoid low energy availability, the balance must be positive. That is, there must be energy available for the body’s physiological processes after subtracting that used for sports. To achieve this, it is very important to:

  • Identify and monitor the symptoms of low energy availability, such as consistently low blood glucose levels, chronic fatigue, decreased performance, amenorrhea, anemia, stress fractures, poor injury recovery, etc. (4).
  • Properly assess dietary intake and body composition to calculate energy availability, as explained earlier.
  • Ensure that the individual’s energy availability is >30 kcal/kg per FFM and aim to maintain optimal levels of 45 kcal/kg per FFM.
  • Gradually increase dietary intake by 300-500 kcal/day if there is low energy availability (5,6).
  • Meet carbohydrate needs (5-7 g/kg/day) and include high-quality proteins (1.2-1.6 g/kg/day), which can vary greatly between individuals (7).
  • Promote post-exercise recovery for good recovery (0.5-1.5 g of carbs per kg of body weight).

In summary, low energy availability is defined as insufficient energy to carry out human physiological processes after subtracting that used for sports. This leads to the immune, reproductive, endocrine systems, etc., being compromised, directly affecting the individual’s health and sports performance.

Consistently low blood glucose levels can be an indicator of low energy availability, and therefore, it is essential to know the athlete’s nutritional needs. These symptoms can be detected and prevented through proper control and nutritional planning. Discover your true energy needs with Glucovibes.

References

  • [1] Weiss Kelly AK, Hecht S; COUNCIL ON SPORTS MEDICINE AND FITNESS. The Female Athlete Triad. Pediatrics. 2016 Aug;138(2):e20160922. doi: 10.1542/peds.2016-0922.
  • [2] Tornberg Å.B., Melin A., Koivula F.M., Johansson A., Skouby S., Faber J., Sjödin A. Reduced neuromuscular performance in amenorrheic elite endurance athletes. Med. Sci. Sports Exerc. 2017;49:2478–2485.
  • [3] Logue DM, Madigan SM, Melin A, Delahunt E, Heinen M, Donnell SM, Corish CA. Low Energy Availability in Athletes 2020: An Updated Narrative Review of Prevalence, Risk, Within-Day Energy Balance, Knowledge, and Impact on Sports Performance. Nutrients. 2020 Mar 20;12(3):835.
  • [4] Nattiv A, Loucks AB, Manore MM, Sanborn CF, Sundgot-Borgen J, Warren MP; American College of Sports Medicine. American College of Sports Medicine position stand. The female athlete triad. Med Sci Sports Exerc. 2007; 39(10):1867-82.
  • [5] Rosen DS, The Committee on Adolescence. Identification and Management of Eating Disorders in Children and Adolescents. Pediatrics 2010; 126 (6) 1240-1253.
  • [6] De Souza MJ, Nattiv A, Joy E, Misra M, Williams NI, Mallinson RJ, Gibbs JC, Olmsted M, Goolsby M, Matheson G, Panel de Expertos.Br J Sports Med. 2014; 48(4):289.
  • [7] Burke, L. M., Hawley, J. A., Wong, S. H., & Jeukendrup, A. E. Carbohydrates for training and competition. Journal of Sports Sciences. 2011; 29 (1), S17-27.