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What is Low Energy Availability and How Do We Calculate It?

Low Energy availability (LEA) underpins Relative Energy Deficiency in Sport (RED-S). It occurs when there is a mismatch in energy consumed (calories) through diet and the energy expended through exercise. When this mismatch occurs there isn’t sufficient energy left to the body to efficiently run functions such as bone, thermoregulation, protein synthesis, immune and reproductive systems.

For active individuals, the cost of exercise can be significant, if this energy expenditure is not accounted for by an increased energy intake it creates low energy availability.

Figure 1. Energy availability is the dietary energy left over to the body after the energy expended from exercise has been accounted for.

How is energy availability calculated?

Energy availability is expressed in a calculation as calories per kilogram of fat free mass. For example, an energy availability of 45 Kcal/KG/FFM means there are 45 calories per kilogram of fat free mass left over to the body for key bodily functions. Assessing energy availability in the field can be fraught with error due to inaccuracies of measuring self reported dietary intake and energy expended during exercise. Such assessments should not be used in isolation to diagnose the health implications of low energy availability. A clinical assessment by a medical professional is the key to diagnosis with additional multi-disciplinary input. Elegant lab controlled studies have demonstrated menstrual dysfunction occurs and an energy availability cut off below 30Kcal/KG/FFM. However recent studies that have assessed athletes in the field have not shown such a clear cut off, most likely due to the inaccuracies described above. Thus further emphasising the importance of clinical management in the diagnosis and recovery of low energy availability.

Figure 2. Example of different levels of energy availability. Energy availability is calculated as Energy consumed (calories) - Energy spent in the exercise (calories)] / kg FFM (fat free mass

Changing energy requirements

Ensuring adequate energy availability day to day means having an understanding of your nutrition requirements across different training scenarios. Just as your training is periodised with variation across the week, your nutrition and fuelling levels need to match this. When trainings become longer and more intense this can significantly increase expenditure that needs to be accommodated for with increased fuelling. A key nutrition behaviour that helps in this regard is focusing on pre, during and post training nutrition. If athletes focus on being organised and committed in this area, as well as eating energy appropriate meals then they will naturally increase their energy intake when training sessions increase in frequency.

Figure 3. Changing energy requirements for different training day scenarios

How we work with our patients to achieve optimal energy availability

Whether working with elite athletes, weekend warriors or those wanting to lose weight ensuring energy availability is optimal for their needs is at the forefront of our nutrition plans. We provide bespoke, periodised plans to help you across your training week. This is then accompanied by fuelling options to ensure you can meet these requirements with each meal and snack that you incorporate.