This week, we take another look at low energy availability (LEA) with a particular interest in male endurance athletes.

Energy Availability (EA) = the energy available for normal physiological functioning once exercise energy expenditure has been accounted for.

i.e. if you consume 2500kcal, burn 1,000kcal in training, you have 1,500kcal left ‘available’.

LEA is the underlying cause of Relative Energy Deficiency in sport (RED-S), which has large detrimental consequences to both sporting performance and health.

Research in LEA is far more advanced in females, where the known threshold for LEA is 30kcal/kg fat free mass (FFM).

For example, a 65kg female athlete with 20% body fat would have 52kcal FFM. Therefore, LEA threshold = 1,560kcal/day.

In male athletes, a clearly defined LEA threshold is lacking.

Identifying RED-S in athletes is relatively straightforward; diagnosing LEA before symptoms arise is more challenging.

During period of energy restriction, energy conservation occurs. This is the sparing of energy at the cost of growth and reproduction. In return, resting metabolic rate (RMR) decreases.

Therefore, being able to identify changes in actual RMR and predicted RMR can be a tool to monitor early onset of LEA in males – this however is difficult to measure. Therefore, cognitive restraint (mind control over food) has been suggested to be a better and more accessible screening tool.

Jurov et al (2022) aimed to establish LEA cut off in healthy male endurance athletes during a single week in preseason. Over the 7 day testing period, calorie intake was estimated and averaged at 3078kcal/day, with an exercise energy expenditure of 1173kcal – therefore, EA was 1,905kcal, giving them an EA score of 29.5kcal/kg/FFM.

Interestingly, 30kcal/kg/FFM is the threshold for LEA in females, however there was no difference in males who consumed above or below this cut off – Meaning that the threshold for males is below females as they are less sensitive to metabolic and psychological disturbances.

Previous research in male athletes suggest that prolonged EA <25 kcal/kg FFM/day could be the critical threshold, but this is yet to be confirmed in male endurance athletes.

That being said, this study confirmed that high cognitive restraint (CR) can be used for early detection in energy conservation, and LEA (High CR = High food restriction).

More interestingly those who had a higher level of CR had lower RMR, which could signify energy conservation and early detection of LEA.

Finally, there was no relationship between performance variables and LEA in this small group of athletes (n=12). Therefore, perhaps performance isn’t the best measure for LEA?

That being said, the development of RED-S is a consequence of LEA over a prolonged period, which this study was not able to detect. However, the use of CR screening and psychological evaluation may be a worthy tool for athletes to identify LEA.